Handgrip strength and risk of malnutrition are associated with an increased risk of hospitalizations in inflammatory bowel disease patients

Background

In patients with inflammatory bowel disease (IBD), frailty is independently associated with mortality and morbidity.

Objectives

This study aimed to extend this work to determine the association between the clinical frailty scale (CFS), handgrip strength (HGS), and malnutrition with IBD-related hospitalizations and surgeries.

Design

IBD patients ⩾18 years of age were prospectively enrolled from two ambulatory care clinics in Alberta, Canada.

Methods

Frailty was defined as a CFS score ⩾4, dynapenia as HGS < 16 kg for females and <27 kg for males, malnutrition using the subjective global assessment (SGA), and the risk of malnutrition using either the abridged patient-generated SGA (abPG-SGA), or the Saskatchewan Inflammatory Bowel Disease Nutrition Risk Tool (SaskIBD-NRT). Logarithm relative hazard graphs and multivariable logistic regression models adjusting for relevant confounders were constructed.

Results

One hundred sixty-one patients (35% ulcerative colitis, 65% Crohn's disease) with a mean age of 42.2 (±15.9) years were followed over a mean period of 43.9 (±10.1) months. Twenty-seven patients were hospitalized, and 13 patients underwent IBD-related surgeries following baseline. While the CFS (aHR 1.34; p = 0.61) and SGA (aHR 0.81; p = 0.69) did not independently predict IBD-related hospitalizations, decreased HGS (aHR 3.96; p = 0.03), increased abPG-SGA score (aHR 1.07; p = 0.03) and a SaskIBD-NRT ⩾ 5 (aHR 4.49; p = 0.02) did. No variable was independently associated with IBD-related surgeries.

Conclusion

HGS, the abPG-SGA, and the SaskIBD-NRT were independently associated with an increased risk of IBD-related hospitalizations. Future studies should aim to validate other frailty assessments in the IBD population in order to better tailor care for all IBD patients.

A204 COST-EFFECTIVENESS OF THERAPIES AFTER FAILURE OF CONVENTIONAL THERAPY FOR PATIENTS WITH MODERATE-TO-SEVERE ULCERATIVE COLITIS IN THE CANADIAN HEALTHCARE SYSTEM

Background

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon which requires ongoing medical therapy. The therapeutic options for moderate-to-severe UC include biologics and small molecules, which are effective but come with a significant cost. As such, their exact positioning in the therapeutic algorithm remains unclear.

Purpose

The aim of our study was to assess and compare the cost-effectiveness of infliximab, adalimumab, vedolizumab, golimumab, ustekinumab and tofacitinib for the management of moderate-to-severe UC from the perspective of the Canadian public healthcare system.

Method

A Markov model was constructed to simulate the disease course of UC patients after initiating each available therapy. Drug costs were obtained from the Alberta Health Drug Benefit List and the remaining costs were determined from the CIHI Patient Cost Estimator. Transition probabilities were obtained from a review of the literature, and loss of response and complication rates were obtained from randomized controlled trials. Our main analysis used a time horizon of 5 years, and time horizons of 1- and 10-years were also assessed in our sensitivity analysis. Probabilistic sensitivity analysis was performed to characterize uncertainty related to all parameters.

Result(s)

Infliximab costs $26,611 per quality-adjusted life year (QALY) using a 5-year time horizon. Adalimumab costs $20,783 per QALY. Vedolizumab costs $40,553 per QALY. Golimumab costs $34,316 per QALY. Ustekinumab costs $26,366 per QALY. Lastly, tofacitinib costs $25,572 per QALY. At a willingness-to-pay threshold of $50,000 per QALY, sensitivity analysis revealed that infliximab, adalimumab, vedolizumab, golimumab, ustekinumab and tofacitinib had a 36%, 12%, 1%, 1%, 44% and 6% probability of being cost-effective, respectively.

Conclusion(s)

Our economic model concluded that adalimumab is the most cost-effective first-line therapy for UC patients who have failed conventional therapy.

Please acknowledge all funding agencies by checking the applicable boxes below

None

Disclosure of Interest

None Declared

A118 BALLOON-ASSISTED ENTEROSCOPY TIMING INCREASES DIAGNOSTIC YIELD IN PATIENTS WITH OVERT OBSCURE GASTROINTESTINAL BLEEDING: A RETROSPECTIVE STUDY

Background

Obscure gastrointestinal bleeding (OGIB) is defined as bleeding from an unknown etiology despite initial investigations with upper endoscopy and colonoscopy, of which 75-80% is attributed to a small bowel (SB) source. OGIB poses a significant diagnostic and therapeutic challenge, resulting in high morbidity and mortality with increased utilization of health care resources. Balloon-assisted enteroscopy (BAE) is a useful procedure for the evaluation and management of small bowel bleeding, with reported diagnostic and therapeutic rates up to 87% and 80%, respectively.

Purpose

This retrospective study aims to evaluate the diagnostic and therapeutic yields in a large cohort of adult patients presenting with different subtypes of OGIB who have undergone BAE, as well as to assess for association between various patient and disease factors, and clinical outcomes.

Method

We performed a retrospective review of 1057 cases of BAE at a large quaternary referral centre between 2016 to 2021 and 158 OGIB cases were identified. Sex, age, and, preprocedural variables including indication, time from video capsule endoscopy (VCE) to BAE and subclassification of SB bleed were collected. Endoscopic modality, findings, and therapeutic interventions were used to calculate diagnostic and therapeutic yields. The association between the timing of BAE relative to VCE and clinical outcomes including rebleeding rate, diagnostics and therapeutic yields were assessed. Bleeding free-survival was estimated using Kaplan-Meier function. All data analyses were performed with SPSS.

Result(s)

The overall diagnostic yield of BAE was 74%. Patients with active overt bleeding were found to have a statistically significant higher yield compared to those with inactive overt bleeding (94% vs 67%, P= 0.03). The therapeutic yield was 51%, with a significantly higher rate of injection therapy and hemoclip placement in those with active overt bleeding compared to those with inactive overt and occult bleeding (P< 0.001). BAE performed within 72 hours of overt GI bleeding was found to have a statistically significant higher diagnostic yield when compared to procedures performed after 72 hours (94% vs 67%, p =0.05). Univariable analysis revealed higher diagnostic yield in patients requiring transfusion within the past 12 months (P= 0.02) Finally, rebleeding-free survival in all patients at 1 year and 5 years was 98% and 68%, respectively.

Image

Conclusion(s)

Balloon-assisted enteroscopy continues to be an effective diagnostic and therapeutic modality for the investigation of obscure gastrointestinal bleeding. Our retrospective study shows a higher diagnostic yield in those presenting with active overt GI bleed as well as those who underwent BAE within 72 hours of overt GI bleeding. Furthermore, patients who required transfusion within the past 12 months are more likely to have a positive BAE finding.

Please acknowledge all funding agencies by checking the applicable boxes below

None

Disclosure of Interest

None Declared

Breastfeeding Patterns in Mothers with Inflammatory Bowel Disease: A Pilot Prospective Longitudinal Study

BACKGROUND

Breastfeeding practices in patients with inflammatory bowel disease (IBD) remain unknown. We aimed to characterize these practices and describe factors that may lead to early discontinuation.

METHODS

This was a pilot, prospective, longitudinal study enrolling mothers with IBD from 2014 to 2017. Patients completed surveys on breastfeeding at time of delivery and up to 12 months postpartum. Breastfeeding discontinuation rates were reported for all patients with IBD and compared between patients with ulcerative colitis and Crohn's disease. Reproductive knowledge was defined using the Crohn's and Colitis Pregnancy Knowledge score. The Mann-Whitney U test assessed for differences between continuous variables, whereas categorical variables were compared using the chi-square test.

RESULTS

A total of 74 mothers with IBD were included, 47 with ulcerative colitis and 27 with Crohn's disease. Breastfeeding rates in mothers with IBD was 94.6% at delivery, 73.9% at 3 months postpartum, 55.2% at 6 months postpartum, and 30.1% at 12 months postpartum. The most common reasons for discontinuing breastfeeding before 6 months postpartum included perceived insufficient milk production and concerns of infant medication exposure through breast milk. Compared with those who continued breastfeeding beyond 6 months postpartum, those who discontinued had lower median Crohn's and Colitis Pregnancy Knowledge scores (14.0 vs 9.0; P = .04).

CONCLUSIONS

Though most mothers with IBD initiate breastfeeding at time of delivery, about half continue beyond 6 months postpartum. Common reasons for this include perceived insufficient milk production and medication concerns. Larger studies are required to validate our findings in more generalizable settings such as primary and secondary care.

A116 CLINICAL OUTCOMES OF PATIENTS UNDERGOING BALLOON-ASSISTED ENDOSCOPY FOR SUSPECTED SMALL BOWEL BLEEDING

Background

Obscure gastrointestinal bleeding (OGIB) accounts for approximately 50% of all GI bleeds. This refers to bleeding from an unknown etiology despite initial investigations with upper endoscopy and colonoscopy, of which 75–80% is attributed to a small bowel source, also termed as small bowel bleeding. Various diagnostic and therapeutic modalities have been used to investigate sources of OGIB. Balloon-assisted enteroscopy (BAE) is a useful procedure for managing small bowel bleeding, with reported diagnostic and therapeutic rates up to 87% and 80%, respectively.

Aims

The aims of this study are to evaluate the outcomes of patients with OGIB who have undergone BAE, as well as to explore correlations between the timing of BAE and clinical outcomes.

Methods

We performed a retrospective review of 342 patients who underwent BAE at a tertiary referral centre between 2016 to 2021, of which 116 underwent evaluation for OGIB. Aside from gender and age, preprocedural variables including endoscopy indication, timing from video capsule endoscopy (VCE) and overt GI bleed were collected to allow for further stratification of data. Endoscopic variables including modality, findings, and therapeutic interventions were used to calculate diagnostic and therapeutic yields. Furthermore, the association between timing of BAE after VCE and clinical outcomes including rebleeding rate, diagnostics and therapeutic yields were assessed. All data analyses were performed with SPSS.

Results

The overall diagnostic yield was 70.3%. Patients with active overt bleeding were found to have a higher yield compared to those with occult and inactive overt bleeding (78.6% vs 72.5% vs 64.6%, respectively). Amongst all OGIB presentations, the most common findings were vascular lesions including angiodysplasia, arteriovenous malformations, and dieulafoy lesions. The majority of lesions were found within the proximal jejunum. Subgroup analysis did not show a statistically significant difference in diagnostic yields between BAE with and without prior VCE (75.9% vs 77.8, P = 0.605). The therapeutic yield was 51.1% with a higher yield found in those presenting with active overt bleeds compared to occult and inactive overt cases. Compared to BAE performed after 30 days of overt GI bleeding, those completed within 30 days was found to have a higher diagnostic and therapeutic rate (80.0% vs 60.0%, 70.0 vs 30.0%, respectively).

Conclusions

Balloon-assisted enteroscopy continues to be an effective diagnostic and therapeutic modality for the investigation of obscure gastrointestinal bleeding. Our retrospective study shows a higher diagnostic and therapeutic rate in those presenting with active overt GI bleed as well as those who underwent BAE within 30 days of overt GI bleeding

Funding Agencies

None

A31 OUTCOMES OF PATIENTS UNDERGOING REPEAT VIDEOCAPSULE ENDOSCOPY (VCE) PRESENTING WITH OBSCURE GASTROINTESTINAL BLEEDING (OGIB)

Background

Videocapsule Endoscopy (VCE) as well as balloon-assisted enteroscopy (BAE) are useful tools in the diagnosis and management of obscure gastrointestinal bleeding (OGIB). There is limited data assessing the diagnostic yield of VCE in subjects with OGIB according to different subtypes: 1) obscure overt 2) inactive overt and 3) active overt.

Aims

We evaluated the diagnostic yield and outcomes of patients undergoing a second VCE in OGIB.

Methods

This is a retrospective analysis of all patients who underwent more than one VCE completed at the University of Alberta from January 1, 2015 to August 31, 2021. Demographic and background information was collected including previous endoscopy results, cross-sectional imaging, and subsequent interventions. Patient data was analyzed according to subtype of OGIB at presentation.

Results

During the study period, there were 59 subjects who met inclusion criteria. The indication for VCE was recurrent iron deficiency anemia (IDA), active OGIB, and/or inactive OGIB in 38 subjects. The median time to VCE after initial endoscopic evaluation was 61 days. Median age of cases was 61.5 years and 49% were female.

Initial VCE had clinically significant positive findings in 68% of cases (Table 1). The diagnostic yield was 75%, 56% and 74% in active OGIB, inactive OGIB, and IDA, respectively. Active bleeding or fresh blood was present in 33% of VCEs for active OGIB compared to 11% of inactive OGIB and 13% of subjects with IDA.

At second VCE investigation, there were positive findings in 42% of cases. Findings on second VCE differed from initial VCE in 17 of 38 cases. Findings that changed clinical management were found in 76% of patients after first and second VCE.

BAEs were performed in 20 subjects after VCE, with therapeutics applied in 75%. The most common findings were arteriovenous malformations (AVMs) (65%) and erosions/ulcers (15%).

Conclusions

The diagnostic yield of VCE is high in appropriately selected patients and did not significantly differ in patients with IDA, active, and inactive OGIB. Serial VCE is appropriate for the investigation of suspected recurrent small bowel bleeding when initial workup is nondiagnostic.

Funding Agencies

None

A160 MOLECULAR ANALYSIS OF THE INJURY-REPAIR RESPONSE IN ULCERATIVE COLITIS REVEALS HETEROGENEITY IN DISEASE ACTIVIT

Background

Ulcerative colitis (UC) is a chronic inflammatory condition affecting the colonic epithelium. We used an established microarray-based system to analyze a set of 128 UC biopsies (113 patients), assessing gene expression associated with the colon’s response to injury in UC.

Aims

Our aim was to describe the burden of injury in UC biopsies and to explore molecular heterogeneity across disease activity, as assessed by the endoscopic Mayo score.

Methods

128 UC colon biopsies were collected at the University of Alberta Hospital (Edmonton, AB) and Cedars-Sinai Hospital (Los Angeles, CA) during standard of care colonoscopy and processed using Affymetrix microarrays. Principal component analysis (PCA) and archetypal analysis (AA) visualized relationships between biopsies and previously annotated injury-associated transcript sets. AA assigned each biopsy to one of three groups, and scores to each biopsy relating it to all three groups.

Results

Spearman correlations (Table 1A) were highest between the endoscopic Mayo score and the injury-repair-associated transcripts (IRRAT, 0.64, P=4.7x10-16), immunoglobulin transcripts highly associated with chronic injury and fibrosis (IGT, 0.63, P=3.0x10-15), endothelial transcripts (ENDAT, 0.61, P=1.8x10-14), and parenchymal dedifferentiation i.e. epithelial solute carrier loss (CT2, -0.60, P=6.5x10-14).

PCA separated injury from no injury in PC1 (Figure 1A). T cell transcripts (QCATs), interferon-gamma inducible transcripts (GRITs) and targets of biologics (IL12, TNFA, ITGA4/B7) separated from injury transcripts in PC2.

We assigned three AA groups and visualized biopsies in PCA (Figure 1B, colored by AA membership). Group 1 (grey, N=44) biopsies had little parenchymal dedifferentiation and low expression of injury-associated transcripts. Groups 2 (red, N=44) and 3 (blue, N=40) had increased expression of injury-associated transcript sets and dedifferentiation compared to Group 1 (Table 1). Although Group 3 was endoscopically similar to Group 1 (P&gt;0.05), Group 3 showed elevated injury-associated transcript set expression (e.g. IRRAT) and increased parenchymal dedifferentiation (CT2).

Conclusions

Assessment of UC biopsies using AA and previously annotated injury-associated gene sets reveals two groups of biopsies that are endoscopically similar though one group has increased molecular abnormalities, thus revealing heterogeneity unrelated to the Mayo score. A molecular system based around PCA and AA could enhance and refine UC disease assessment by allowing for quantitation and qualification of injury in biopsies obtained at endoscopy i.e. a level of resolution beyond conventional endoscopic scoring.

Funding Agencies

None

A93 USEFULNESS OF A NOVEL SMARTPHONE APP IN GASTROINTESTINAL ENDOSCOPY TO TRACK PROCEDURE NUMBERS AND THERAPEUTIC INTERVENTIONS

Background

Endoscopy teaching is an integral part of gastroenterology (GI) training. Though the number of completed endoscopic procedures does not equate competency, procedure tracking is useful for monitoring an individual’s learning progress. Currently, procedure tracking is typically done on an informal basis using paper or electronic spreadsheets. These methods are non-standardized and may not be shareable between trainees and their programs.

Endostation is a smartphone app created by the University of Alberta Therapeutic Endoscopy Program to facilitate the tracking of endoscopic procedures. The app allows trainees to record the number of endoscopies and details such as cecal intubation (CI), ERCP cannulation, and therapeutic interventions. Data can be accessed by users via the app and website (www.endostation.ca), allowing for close monitoring of trainees’ learning progress.

Aims

Our primary objective was to evaluate the usefulness of the app for tracking the number of endoscopic procedures and therapeutic interventions. Our secondary objective was to evaluate the acquisition of endoscopy skills based on quality endoscopic parameters such as CI rate and ERCP cannulation rate.

Methods

One therapeutic endoscopy fellow and two GI residents were recruited for the study. Participants were asked to document their procedures over the study period (9-month for therapeutic endoscopy fellow, 12-month for GI residents). Total number of procedures was summed for each trainee. Acquisition of endoscopy skills was tracked by comparing success rates of CI and ERCP cannulation at different points within the study period.

Results

The therapeutic endoscopy fellow recorded 415 cannulation attempts, 209 sphincterotomies, 282 stone extractions, 71 plastic stent placements, and 37 metal stent placements. There was a significant difference in the cannulation success rate when comparing the 1^st trimester and the 3^rd trimester of the study period (68% vs 85%; p= 0.0012) (Fig 1).

The two GI residents respectively recorded 335 and 170 colonoscopies plus 454 and 305 gastroscopies. Resident 1 recorded 58 polypectomies, 9 esophageal variceal banding, and 16 non-variceal hemostasis. Resident 2 recorded 17 polypectomies, 12 esophageal variceal banding, and 9 non-variceal hemostasis. The CI success rate was significantly higher for both residents when comparing the first 4 months of training vs the last 4 months [24% vs 88% for resident 1 (p=0.00001); 15% vs 42% for resident 2 (p= 0.001)] (Fig 1).

Conclusions

The smartphone app (Endostation) was a useful tool for endoscopic procedure tracking. Data from the app was useful in demonstrating improvement in CI rate and ERCP cannulation rate over the study period.

Funding Agencies

None

A146 THE EFFECTIVENESS OF USTEKINUMAB DOSE ESCALATION IN PATIENTS WITH ULCERATIVE COLITIS

Background

Ustekinumab (UST), an IgG1 antibody that targets IL-12/23, is an effective and safe treatment option for patients with inflammatory bowel disease (IBD). Cohort studies have shown that dose escalation is an effective strategy for reinducing and maintaining remission in Crohn’s disease patients who do not respond or lose response to standard dosing of UST. There are currently no published studies evaluating effectiveness of UST dose escalation in ulcerative colitis (UC) patients.

Aims

To assess the effectiveness of UST dose escalation in patients with moderate-to-severe UC who have not responded to or lost responsiveness to standard maintenance dosing (90mg SC every 8 weeks).

Methods

A retrospective cohort study was conducted at three centers. Consecutive patients with moderate-to-severe UC initiated on ustekinumab were enrolled.

Results

Data on 43 patients (26 males) are reported (to date, patients from 1 of 3 centres have been reviewed). Mean age was 40.2 years (±15.6). Mean duration of disease was 8.5 years (±5.8). Mean duration of follow up while on UST was 8.8 months (±7.2). In total, 28% (12) of patients underwent dose escalation: 8% (1) by way of IV reinduction, 58% (7) through interval shortening (every 4 weeks), and 33% (4) by both interval shortening and IV reinduction. Mean time to first dose escalation was 6.2 months (±4.1). Mean time to second dose escalation was 5.1 months (±1.2). Seven percent (3) of patients discontinued UST, with the mean timeframe being 5.3 months (±2.9). Three patients discontinued UST due to primary non-response with one proceeding onto surgery.

Time to normalization of CRP and FCP after initiation of UST is shown in Table 1.

Conclusions

Preliminary data demonstrates that 28% of patients in this cohort required UST dose escalation, with 33% requiring a second dose escalation. Only 7% of patients discontinued UST at 9 months of follow up. Longer term follow up of this cohort would determine if dose escalation is an effective strategy to extend durability of ustekinumab.

Table 1. Normalization of CRP and FCP

Funding Agencies

None

A57 ULCERATIVE COLITIS DISEASE ACTIVITY IS DOMINATED BY INNATE IMMUNITY AND FEATURES OF TISSUE REMODELING

Background

Ulcerative colitis (UC) is a chronic inflammatory condition affecting the colonic epithelium, with potential roles for the inflammasome, complement activation, T cells, and the microbiome in pathogenesis. We applied an established method of microarray-based gene expression analysis to a set of 128 UC biopsies (from 113 patients), to elucidate the molecular changes associated with active UC.

Aims

Our aim was to describe the molecules most associated with UC disease activity (the endoscopic Mayo score) and to annotate these molecules into biological processes.

Methods

128 UC colonic biopsies were collected at the University of Alberta Hospital (Edmonton, Alberta) and Cedars-Sinai Hospital (Los Angeles, California) during standard of care colonoscopy. Biopsies were processed using Affymetrix microarrays. Gene expression data from the population was visualized using volcano plots (showing fold change and association between genes and endoscopic Mayo score), and heatmaps (showing expression of the top 30 genes in a previously established cell panel). Overexpression of top genes was analyzed using Gene Ontology and KEGG pathways.

Results

The volcano plot (Figure 1A) showed strong associations between the endoscopic Mayo score and components of innate immunity, e.g. complement factor B (CFB), C1-inhibitor (also known as SERPING1), chitinase 3-like 1 (CHI3L1), and inflammasome genes (ZBP1 and PIM2). Moderate associations with calprotectin (S100A8 and S100A9), other inflammasome components (CASP1 and NLRP3), and T cell transcripts (i.e. CTLA4, PDL1) were observed. Targets of biologic therapy (TNFA, ITGA4/B7, IL12B) were weakly associated with the endoscopic Mayo score.

Expression of the top genes in a cell panel (Figure 1B) showed primary expression in monocytes, macrophages, dendritic cells, and polymorphonucleocytes, with some expression in colon epithelial and endothelial cells. Minimal expression was found in CD4/CD8 T cells or NK cells.

Pathway analysis represented extracellular matrix remodeling, complement regulation, and TNFA signaling, but revealed no pathways associated with adaptive immunity (Table 1).

Conclusions

UC disease activity, as assessed by the endoscopic Mayo score, was strongly associated with tissue remodeling and molecules of innate immunity that were largely found in myeloid cells, colon epithelium, and endothelium. Cognate T cells were not dominant features of UC disease activity. These data suggest that the driver of ongoing UC activity is independent of the cognate T cell response.

Funding Agencies

None

Using Patient Completed Screening Tools to Predict Risk of Malnutrition in Patients With Inflammatory Bowel Disease

Background

Malnutrition is associated with adverse clinical outcomes in patients with inflammatory bowel disease (IBD), however, malnutrition screening is not routinely performed. This study aimed to identify the prevalence of malnutrition in patients with IBD and compare the accuracy of patient completed screens to a gold-standard malnutrition assessment tool: the dietitian-completed subjective global assessment (SGA).

Methods

This cross-sectional study was conducted at 2 hospitals and 2 ambulatory care clinics in Alberta, Canada. Patients with IBD completed 4 malnutrition screening tools: abridged patient-generated SGA (abPG-SGA), Malnutrition Universal Screening Tool (MUST), Canadian Nutrition Screening Tool (CNST), and Saskatchewan IBD-nutrition risk (SaskIBD-NR). Risk of malnutrition was calculated for each tool and differences were compared between IBD subtype and body mass index (BMI) categories. Sensitivity and specificity, negative and positive predictive values (NPV and PPV), and area under the receiver operating characteristic curve (AUC) were calculated compared to SGA.

Results

Patients with Crohn's disease (n = 149) and ulcerative colitis (n = 96) participated in this study. Overall prevalence of malnutrition using SGA was 23% and malnutrition risk for CNST, abPG-SGA, SaskIBD-NR, and MUST was 37%, 36%, 36%, and 27%, respectively. Overall, the abPG-SGA had the highest sensitivity (83%), PPV (53%), and NPV (94%), and largest AUC (0.837) compared to SGA. For patients with a BMI ≥25 kg/m², sensitivity and PPV of the abPG-SGA decreased to 73% and 41%, respectively, with a AUC of 0.841.

Conclusions

Malnutrition is prevalent in patients with IBD and using malnutrition risk screening tools such as the abPG-SGA may be useful to identify patients who would benefit from further assessment.

Combination Therapy Does Not Improve Rate of Clinical or Endoscopic Remission in Patients with Inflammatory Bowel Diseases Treated With Vedolizumab or Ustekinumab

BACKGROUND & AIMS

Patients with Crohn's disease (CD) or ulcerative colitis (UC) often receive combination therapy with an immunomodulator and tumor necrosis factor antagonists, especially infliximab. However, the benefits of combination therapy with vedolizumab and ustekinumab are unclear.

METHODS

We performed a retrospective study of patients with CD or UC initiating vedolizumab or ustekinumab therapy at Massachusetts General Hospital (USA), Alberta Health Sciences (Canada), or Nancy University Hospital (France) with at least 1 year of follow up. The primary outcome was clinical remission or response at week 14, based on the Harvey Bradshaw index for CD or simple clinical colitis index or partial Mayo score for UC. We separately examined week 30 and week 54 clinical outcomes, endoscopic response, and durability of therapy using multivariable regression models and adjusting for relevant confounders.

RESULTS

Our study included 549 patients (263 with UC, 286 with CD) receiving maintenance therapy with vedolizumab and 363 patients (4 with UC, 359 with CD) receiving maintenance therapy with ustekinumab with 1 year of follow up. The mean disease duration was 13-15 years. One-hundred thirty-one patients receiving vedolizumab (23.9%; 78 receiving thiopurine, 53 receiving methotrexate) and 120 patients receiving ustekinumab (33.1%, 57 receiving thiopurine, 63 receiving methotrexate) were receiving combination therapy. For vedolizumab, there was no difference in clinical response or remission with combination therapy vs monotherapy at week 14 (68.2% vs 74.1%; P = .22), week 30 (74.3% vs 75.6%; P = .78) or week 54 (78.3% vs 72.9%, P = .33). For ustekinumab, there was no difference in clinical response or remission with combination therapy vs monotherapy at week 14 (54.6% vs 65.8%; P = .08), week 30 (71.6% vs 77.4%; P = .33) or week 54 (62.1% vs 67.0%; P = .52). There were similar proportions of patients remaining on treatment or with endoscopic response at 1 year among patients receiving combination or monotherapy with vedolizumab or ustekinumab.

CONCLUSIONS

In patients with CD or UC initiating ustekinumab or vedolizumab therapy, combination therapy with immunomodulators did not increase rates of clinical remission or response, endoscopic remission, or persistence of therapy at 1 year.

Fecal Calprotectin May Predict Adverse Pregnancy-Related Outcomes in Patients with Inflammatory Bowel Disease

BACKGROUND

The role of fecal calprotectin in predicting pregnancy-related outcomes in inflammatory bowel disease (IBD) remains unknown.

AIM

To determine whether increased fecal calprotectin during pregnancy is associated with adverse pregnancy outcomes in IBD.

METHODS

This is a multicenter cohort study of women with IBD who underwent fecal calprotectin monitoring during pregnancy. Fecal calprotectin levels were stratified by trimester, and adverse pregnancy-related outcomes were recorded. The Mann-Whitney U test assessed differences between continuous variables, whereas categorical variables were compared using the Chi-squared test.

RESULTS

Eighty-five women with IBD were included. First trimester fecal calprotectin was higher in patients who underwent emergency Cesarean birth compared to those who had a vaginal delivery (503 ug/g, IQR 1554.3 ug/g vs. 130 ug/g, IQR 482 ug/g, p = .030, respectively) and in those who delivered infants with low birth weight compared to normal birth weight (1511 ug/g, IQR 579 ug/g vs. 168 ug/g, IQR 413 ug/g, p = .049, respectively). Third trimester fecal calprotectin was higher in those with non-elective induction of labor (334.5 ug/g, IQR 1411.0 ug/g) compared to those with spontaneous delivery (116.5 ug/g, IQR 227.1 ug/g) (p = .025). Those with a fecal calprotectin ≥ 250 ug/g in the second trimester had an increased incidence of infants with low birth weight (35.3% vs. 3.8%) (p = .049), whereas those with a fecal calprotectin ≥ 250 ug/g in the third trimester had an increased incidence of non-elective induction of labor (43.8% vs. 10.3%, p = .030).

CONCLUSIONS

Fecal calprotectin may be a useful noninvasive marker to predict adverse pregnancy-related outcomes in patients with IBD.

A163 MAJORITY OF INFLAMMATORY BOWEL DISEASE PATIENTS WITH RECURRENT CLOSTRIDIOIDES INFECTION DO NOT REQUIRE FECAL MICROBIOTA TRANSPLANTATION

Background

Patients with inflammatory bowel disease (IBD) are at increased risk of developing Clostridioides difficile infection (CDI) and have worse outcomes including higher rates of colectomy and death, and experience higher rates of recurrent CDI (rCDI). However, it is still not clear whether rCDI is a cause of refractory IBD or a consequence of the inflammatory state in the colon.

Aims

We aimed to assess the outcomes of rCDI in patients with active IBD compared to inactive IBD in the era of fecal microbiota transplantation (FMT)

Methods

This is a retrospective cohort of adult IBD patients with rCDI at the IBD centre at the University of Alberta hospital between 2014–2017. rCDI was defined as a recurrent episode occurring within 60 days of the prior after successful treatment with antibiotics. We collected demographic and clinical characteristics, along with the rCDI-related and FMT outcomes in patients with active and inactive IBD. Active IBD was based on clinical assessment using a combination of disease severity scores (Harvey Bradshaw Index, partial Mayo scores), presence of active disease on colonoscopy, clinical symptoms and/or treatment escalation or change in the month leading up to rCDI diagnosis.

Results

Over the study period, 56 IBD patients (50% ulcerative colitis, 28/56) had a total of 85 rCDI episodes. Thirty-four percent (19/56) of patients had two or more rCDI episodes. Forty-one percent (35/85) of rCDI episodes were toxin positive while the remainder were only PCR positive. Thirty-nine percent (33/85) had active IBD at the time of CDI diagnosis. Patients with active IBD were more likely to have rCDI (1.7 rCDI episodes vs. 1.5, p=0.018). IBD treatment escalation was also more likely in the active IBD cases (79% vs. 44%, p = 0.002) with the use of steroids (27% vs 2%, p = 0.001) and addition of biologics (18% vs. 2%, p = 0.013). Active IBD cases were also more likely to be hospitalized (30% vs. 10%, p = 0.02) and were more likely to receive FMT (27% vs. 4%, p = 0.003). There was no difference in the time between rCDI episodes, antibiotic exposure or colectomy rates between the two groups.

Conclusions

Compared to IBD patients in remission, patients with active IBD are more likely to experience rCDI, IBD treatment escalation and FMT. It is interesting to note that only 27% of patients with recurrent CDI required FMT suggesting CDI may be a marker of active or refractory disease rather than a cause. Larger, prospective studies are needed to help clarify this association.

Funding Agencies

None

Systematic review with meta-analysis: efficacy of balloon-assisted enteroscopy for dilation of small bowel Crohn's disease strictures

BACKGROUND

Evidence for endoscopic balloon dilation of small intestinal strictures in Crohn's disease (CD) using balloon-assisted enteroscopy is scarce.

AIM

To evaluate endoscopic balloon dilation for the treatment of small intestinal CD strictures using balloon-assisted enteroscopy.

METHODS

Citations in Embase, MEDLINE, and Cochrane were systematically reviewed. In a meta-analysis of 18 studies with 463 patients and 1189 endoscopic balloon dilations, technical success was defined as the ability to dilate a stricture. Individual data were also obtained on 218 patients to identify outcome-relevant risk factors.

RESULTS

In the pooled per-study analysis, technical success rate of endoscopic balloon dilation was 94.9%, resulting in short-term clinical efficacy in 82.3% of patients. Major complications occurred in 5.3% of patients. During follow-up, 48.3% of patients reported symptom recurrence, 38.8% were re-dilated and 27.4% proceeded to surgery. On the per-patient-based multivariable analysis, that patients with disease activity in the small intestine had lower short-term clinical efficacy (odds ratio 0.32; 95% confidence interval 0.14-0.73, P = 0.007). Patients with concomitant active disease in the small and/or large intestine had an increased risk to proceed toward surgery (hazard ratio 1.85; 95% confidence interval 1.09-3.13, P = 0.02 and hazard ratio 1.77; 95% confidence interval 1.34-2.34, P < 0.001).

CONCLUSIONS

Balloon-assisted enteroscopy for dilatation of CD-associated small intestinal strictures has high short-term technical and clinical efficacy and low complication rates. However, up to two-thirds of patients need re-dilation or surgery.

A222 EPIDEMIOLOGICAL, PHENOTYPIC AND CLINICAL PATTERNS OF EXTRAINTESTINAL MANIFESTATIONS IN INFLAMMATORY BOWEL DISEASE

Background

Inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), may affect multiple organ systems. The extraintestinal manifestations (EIMs) occur frequently, considerably increase morbidity and mortality, and strongly influence the quality of life in IBD patients.

Aims

To establish the all-time prevalence of EIMs in a large cohort of IBD patients and assess risk factors contributing to their development.

Methods

We conducted a retrospective cohort study of IBD patients followed at the Division of Gastroenterology, University of Alberta, diagnosed between 1954 and 2019. We recorded demographic, clinical, and biochemical data. The EIMs included dermatological, musculoskeletal, ophthalmological, hepatobiliary, urogenital, and pulmonary manifestations. The chi-square and Mann-Whitney tests (median, IQR) were used to evaluate differences. Univariate logistic regression was used to determine the association of EIMs with demographic and disease-specific variables across CD and UC, with predictors (p≤0.05) further incorporated into multivariate regression models.

Results

We analyzed data of 4493 IBD patients: 2354 with CD and 2139 – with UC, aged 18–96 years. Males were underrepresented in the CD cohort compared to the UC (47.8% vs 52.8%; p=0.001), with longer disease duration (16.3, IQR 16.1 vs 12.3, IQR 12.4 years; p≤0.001). The EIMs were slightly more prevalent in the CD group compared to UC (22.2% vs 20.4%; p=0.134), along with a significantly higher proportion of patients with over two EIMs (4.1% vs 1.7%; p≤0.001). The EIMs’ pattern varied substantially between the IBD subtypes (Figure). In the CD cohort, the most common EIM was peripheral arthropathy (4.1%), followed by ankylosing spondylitis (4.0%) and nephrolithiasis (3.6%). Among CD patients, disease duration ≥20 years (OR 1.70, 95% CI 1.17–2.48; p=0.006), iron (OR 1.54, 95%CI 1.13–2.09; p=0.006) and calcium (OR 2.28, 95% CI 1.21–4.27; p=0.010) deficiencies were identified as risk factors for EIMs. The UC patients most frequently had primary sclerosing cholangitis (9.6%) with peripheral arthropathy and nephrolithiasis each being present in 2.2% of patients. In the UC cohort, three variables demonstrated the most significant associations with EIMs: male sex (OR 1.75, 95% CI 1.32–2.32; p≤0.001), disease duration ≥20 years (OR 1.93, 95% CI 1.35–2.74; p≤0.001), and pan-colonic disease extent (OR 2.12, 95% CI 1.03–4.36; p=0.041) (Table).

Conclusions

Our data demonstrate that over one-fifth of IBD patients had at least one EIM over the course of the disease and the EIMs pattern varies substantially across CD and UC. Identification of risk factors allowing prediction of EIMs would increase awareness, assist in their early recognition, and tailor further management.

Funding Agencies

AbbVie

Canadian Association of Gastroenterology Clinical Practice Guideline for the Management of Luminal Crohn's Disease

BACKGROUND & AIMS

Crohn's disease (CD) is a lifelong illness with substantial morbidity, although new therapies and treatment paradigms have been developed. We provide guidance for treatment of ambulatory patients with mild to severe active luminal CD.

METHODS

We performed a systematic review to identify published studies of the management of CD. The quality of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development and Evaluation (GRADE) approach. Statements were developed through an iterative online platform and then finalized and voted on by a group of specialists.

RESULTS

The consensus includes 41 statements focused on 6 main drug classes: antibiotics, 5-aminosalicylate, corticosteroids, immunosuppressants, biologic therapies, and other therapies. The group suggested against the use of antibiotics or 5-aminosalicylate as induction or maintenance therapies. Corticosteroid therapies (including budesonide) can be used as induction, but not maintenance therapies. Among immunosuppressants, thiopurines should not be used for induction, but can be used for maintenance therapy for selected low-risk patients. Parenteral methotrexate was proposed for induction and maintenance therapy in patients with corticosteroid-dependent CD. Biologic agents, including tumor necrosis factor antagonists, vedolizumab, and ustekinumab, were recommended for patients failed by conventional induction therapies and as maintenance therapy. The consensus group was unable to clearly define the role of concomitant immunosuppressant therapies in initiation of treatment with a biologic agent.

CONCLUSIONS

Optimal management of CD requires careful patient assessment, acknowledgement of patient preferences, evidence-based use of existing therapies, and thorough assessment to define treatment success.

Systematic review of nutrition screening and assessment in inflammatory bowel disease

BACKGROUND

Malnutrition is prevalent in inflammatory bowel disease (IBD). Multiple nutrition screening (NST) and assessment tools (NAT) have been developed for general populations, but the evidence in patients with IBD remains unclear.

AIM

To systematically review the prevalence of abnormalities on NSTs and NATs, whether NSTs are associated with NATs, and whether they predict clinical outcomes in patients with IBD.

METHODS

Comprehensive searches performed in Medline, CINAHL Plus and PubMed. Included: English language studies correlating NSTs with NATs or NSTs/NATs with clinical outcomes in IBD. Excluded: Review articles/case studies; use of body mass index/laboratory values as sole NST/NAT; age < 16.

RESULTS

Of 16 studies and 1618 patients were included, 72% Crohn’s disease and 28% ulcerative colitis. Four NSTs (the Malnutrition Universal Screening Tool, Malnutrition Inflammation Risk Tool (MIRT), Saskatchewan Inflammatory Bowel Disease Nutrition Risk Tool (SaskIBD-NRT) and Nutrition Risk Screening 2002 (NRS-2002) were significantly associated with nutritional assessment measures of sarcopenia and the Subjective Global Assessment (SGA). Three NSTs (MIRT, NRS-2002 and Nutritional Risk Index) were associated with clinical outcomes including hospitalizations, need for surgery, disease flares, and length of stay (LOS). Sarcopenia was the most commonly evaluated NAT associated with outcomes including the need for surgery and post-operative complications. The SGA was not associated with clinical outcomes aside from LOS.

CONCLUSION

There is limited evidence correlating NSTs, NATs and clinical outcomes in IBD. Although studies support the association of NSTs/NATs with relevant outcomes, the heterogeneity calls for further studies before an optimal tool can be recommended. The NRS-2002, measures of sarcopenia and developments of novel NSTs/NATs, such as the MIRT, represent key, clinically-relevant areas for future exploration.

Early Initiation of Tumor Necrosis Factor Antagonist-Based Therapy for Patients With Crohn's Disease Reduces Costs Compared With Late Initiation

BACKGROUND & AIMS

Antagonists of tumor necrosis factor (TNF) are effective for induction and maintenance of remission of Crohn's disease (CD) and are generally prescribed when patients do not respond to conventional, less-costly medical therapies. Early initiation of anti-TNF therapy reduced rates of surgery and dose escalation due to loss of response. However, these drugs are expensive, so studies are needed on the cost effectiveness of early initiation. We aimed to determine the cost effectiveness of initiating treatment early in the disease course (within 2 years of CD diagnosis) vs later in the disease course (more than 2 years after diagnosis).

METHODS

We constructed a Markov model of a hypothetical cohort of patients with CD in Canada to simulate disease progression after initiation of infliximab or adalimumab therapy. We used published loss-of-response rates to compare the lifetime cost effectiveness of early vs late initiation of anti-TNF therapies. Transition probabilities and utilities were obtained through a literature search, and costs were obtained from the Alberta Ministry of Health. Sensitivity analysis was used to characterize uncertainty.

RESULTS

Early initiation of infliximab yielded an additional 0.72 quality-adjusted life-years (QALYs) and saved $50,418 compared with late initiation. Early initiation of adalimumab yielded an additional 0.54 QALYs and saved $43,969. At a willingness-to-pay threshold of $50,000, early initiations of infliximab or adalimumab therapy had a 74% chance of being cost effective compared with late initiation.

CONCLUSIONS

In a Markov model analysis, we found initiation of either infliximab or adalimumab within 2 years of CD diagnosis to provide significant cost savings and QALYs compared with later initiation (more than 2 years after diagnosis).

Clinical Practice Guideline for the Medical Management of Perianal Fistulizing Crohn's Disease: The Toronto Consensus

BACKGROUND

Fistulas occur in about 25% of patients with Crohn's disease (CD) and can be difficult to treat. The aim of this consensus was to provide guidance for the management of patients with perianal fistulizing CD.

METHODS

A systematic literature search identified studies on the management of fistulizing CD. The quality of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development and Evaluation (GRADE) approach. Statements were developed through an iterative online platform using a modified Delphi process, then finalized, and voted on by a group of specialists.

RESULTS

The quality of evidence for treatment of fistulizing CD was generally of very low quality, and because of the scarcity of good randomized controlled trials (RCTs), these consensus statements generally provide conditional suggestions (5 of 7 statements). Imaging and surgical consultations were recommended in the initial assessment of patients with active fistulizing CD, particularly those with complicated disease. Antibiotic therapy is useful for initial symptom control. Antitumor necrosis factor (anti-TNF) therapy was recommended to induce symptomatic response, and continued use was suggested to achieve and maintain complete remission. The use of concomitant immunosuppressant therapies may be useful to optimize pharmacokinetic parameters when initiating anti-TNF therapy. When there has been an inadequate symptomatic response to medical management strategies, surgical therapy may provide effective fistula healing for some patients.

CONCLUSIONS

Optimal management of perianal fistulizing CD requires a collaborative effort between gastroenterologists and surgeons and may include the evidence-based use of existing therapies, as well as surgical assessments and interventions when needed. 10.1093/ibd/izy247_video1izy247.video15978518763001.

Innovative Online Educational Portal Improves Disease-Specific Reproductive Knowledge Among Patients With Inflammatory Bowel Disease

BACKGROUND

Inflammatory bowel disease (IBD) is often diagnosed in early adulthood, affecting patients through their reproductive years. Many patients, lacking knowledge about IBD and reproduction, make uninformed decisions. Although patients have turned to the Internet for information, it remains unclear if online resources are effective for improving and retaining IBD-specific reproductive knowledge. We aimed to elucidate if a multimedia vs text-only online educational intervention could improve IBD-specific reproductive knowledge for more than 6 months.

METHODS

We developed a website covering genetics, fertility, surgery, pregnancy, medications, delivery, and postpartum in the context of IBD. Adult IBD patients were randomized into study groups (multimedia or text-only) and provided 60-day access. Participants completed pre-, post-, and 6+ month-postintervention pregnancy knowledge (CCPKnow) questionnaires. Results were compared using nonparametric tests.

RESULTS

Of 111 registered participants, 78 (70.3%) completed pre- and postintervention questionnaires, and 37 (47.4%) subsequently completed the 6+ month questionnaire. Demographics were as follows: median age (interquartile range [IQR]) 29.3 (25.6-32.9) years, Crohn's disease n = 54 (69.2%), females n = 63 (80.3%), of which n = 5 (7.9%) were pregnant and n = 19 (30.2%) had previously been pregnant. The median CCPKnow scores (/17) (IQR) were 8.0 (3.0-10.0) pre-intervention, 16.0 (13.00-17.00) postintervention, and 14.0 (12.0-15.0) 6+ months postintervention. The median within-subject increase in score was 6.5 pre- to postintervention, and 4.0 pre- to 6+ months postintervention (both P < 0.001). The median increase in score (pre- to post-) was 8.0 for the multimedia group and 6.0 for the text-only group (P = 0.216).

CONCLUSIONS

An evidence-based, online educational portal can significantly improve and maintain IBD-specific reproductive patient knowledge for more than 6 months.

Clinical Practice Guideline for the Medical Management of Perianal Fistulizing Crohn's Disease: The Toronto Consensus

Background

Fistulas occur in about 25% of patients with Crohn's disease (CD) and can be difficult to treat. The aim of this consensus was to provide guidance for the management of patients with perianal fistulizing CD.

Methods

A systematic literature search identified studies on the management of fistulizing CD. The quality of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development and Evaluation (GRADE) approach. Statements were developed through an iterative online platform using a modified Delphi process, then finalized, and voted on by a group of specialists.

Results

The quality of evidence for treatment of fistulizing CD was generally of very low quality, and because of the scarcity of good randomized controlled trials (RCTs), these consensus statements generally provide conditional suggestions (5 of 7 statements). Imaging and surgical consultations were recommended in the initial assessment of patients with active fistulizing CD, particularly those with complicated disease. Antibiotic therapy is useful for initial symptom control. Antitumor necrosis factor (anti-TNF) therapy was recommended to induce symptomatic response, and continued use was suggested to achieve and maintain complete remission. The use of concomitant immunosuppressant therapies may be useful to optimize pharmacokinetic parameters when initiating anti-TNF therapy. When there has been an inadequate symptomatic response to medical management strategies, surgical therapy may provide effective fistula healing for some patients.

Conclusions

Optimal management of perianal fistulizing CD requires a collaborative effort between gastroenterologists and surgeons and may include the evidence-based use of existing therapies, as well as surgical assessments and interventions when needed.

Canadian Association of Gastroenterology Clinical Practice Guideline for the Management of Luminal Crohn's Disease

Background & Aims

Crohn’s disease (CD) is a lifelong illness with substantial morbidity, although new therapies and treatment paradigms have been developed. We provide guidance for treatment of ambulatory patients with mild to severe active luminal CD.

Methods

We performed a systematic review to identify published studies of the management of CD. The quality of evidence and strength of recommendations were rated according to the Grading of Recommendation Assessment, Development and Evaluation (GRADE) approach. Statements were developed through an iterative online platform and then finalized and voted on by a group of specialists.

Results

The consensus includes 41 statements focused on 6 main drug classes: antibiotics, 5-aminosalicylate, corticosteroids, immunosuppressants, biologic therapies, and other therapies. The group suggested against the use of antibiotics or 5-aminosalicylate as induction or maintenance therapies. Corticosteroid therapies (including budesonide) can be used as induction, but not maintenance therapies. Among immunosuppressants, thiopurines should not be used for induction, but can be used for maintenance therapy for selected low-risk patients. Parenteral methotrexate was proposed for induction and maintenance therapy in patients with corticosteroid-dependent CD. Biologic agents, including tumor necrosis factor antagonists, vedolizumab, and ustekinumab, were recommended for patients failed by conventional induction therapies and as maintenance therapy. The consensus group was unable to clearly define the role of concomitant immunosuppressant therapies in initiation of treatment with a biologic agent.

Conclusions

Optimal management of CD requires careful patient assessment, acknowledgement of patient preferences, evidence-based use of existing therapies, and thorough assessment to define treatment success.

A Cholangioscopy-Based Novel Classification System for the Phenotypic Stratification of Dominant Bile Duct Strictures in Primary Sclerosing Cholangitis-the Edmonton Classification

Background

Primary sclerosing cholangitis (PSC) is a chronic inflammatory condition causing bile duct strictures. Differentiating inflammatory strictures from malignant transformation is challenging. Cholangioscopy allows direct visualization with the option to biopsy. We describe our experience of cholangioscopy in PSC and propose a novel stricture classification system based on cholangioscopic findings.

Methods

All patients with PSC and a dominant stricture referred for cholangioscopy were reviewed. Based on visual characteristics with direct cholangioscopy, we propose a novel classification system for the extrahepatic form of PSC.

Results

The proposed Edmonton Classification system for extrahepatic PSC strictures consists of the following phenotypes: 1) ‘inflammatory type’, with mucosal erythema and active inflammatory exudate, 2) ‘fibro-stenotic type’, with concentric fibrotic scars, and 3) ‘nodular or mass-forming type’, with a mass in the involved segment of extrahepatic bile duct. From 2011–2017, 30 patients with PSC and a dominant stricture (21 M, mean age 46 years) underwent 32 cholangioscopy procedures. Cholangioscopy was technically successful in 29 of 32 procedures (91%). In these 29 stricture cases, inflammatory type was seen in 16 (55%), fibro-stenotic type in seven (24%) and nodular or mass-forming type in five (17%). In one (4%) procedure, there was no stricture or abnormality identified.

Conclusion

Cholangioscopy is effective and safe for the evaluation of dominant biliary strictures in PSC. Based on our experience with cholangioscopy, we propose a novel classification system of extrahepatic PSC phenotypes: the Edmonton Classification.

Dried plum diet protects from bone loss caused by ionizing radiation

Bone loss caused by ionizing radiation is a potential health concern for radiotherapy patients, radiation workers and astronauts. In animal studies, exposure to ionizing radiation increases oxidative damage in skeletal tissues, and results in an imbalance in bone remodeling initiated by increased bone-resorbing osteoclasts. Therefore, we evaluated various candidate interventions with antioxidant or anti-inflammatory activities (antioxidant cocktail, dihydrolipoic acid, ibuprofen, dried plum) both for their ability to blunt the expression of resorption-related genes in marrow cells after irradiation with either gamma rays (photons, 2 Gy) or simulated space radiation (protons and heavy ions, 1 Gy) and to prevent bone loss. Dried plum was most effective in reducing the expression of genes related to bone resorption (Nfe2l2, Rankl, Mcp1, Opg, TNF-α) and also preventing later cancellous bone decrements caused by irradiation with either photons or heavy ions. Thus, dietary supplementation with DP may prevent the skeletal effects of radiation exposures either in space or on Earth.

Inflammation and epithelial cell injury in AIDS enteropathy: involvement of endoplasmic reticulum stress

Immunosuppressive lentivirus infections, including human, simian, and feline immunodeficiency viruses (HIV, SIV, and FIV, respectively), cause the acquired immunodeficiency syndrome (AIDS), frequently associated with AIDS enteropathy. Herein, we investigated the extent to which lentivirus infections affected mucosal integrity and intestinal permeability in conjunction with immune responses and activation of endoplasmic reticulum (ER) stress pathways. Duodenal biopsies from individuals with HIV/AIDS exhibited induction of IL-1β, CD3ε, HLA-DRA, spliced XBP-1(Xbp-1s), and CHOP expression compared to uninfected persons (P<0.05). Gut epithelial cells exposed to HIV-1 Vpr demonstrated elevated TNF-α, IL-1β, spliced Xbp-1s, and CHOP expression (P<0.05) together with calcium activation and disruption of epithelial cell monolayer permeability. In addition to reduced blood CD4(+) T lymphocyte levels, viral loads in the gut and plasma were high in FIV-infected animals (P<0.05). FIV-infected animals also exhibited a failure to gain weight and increased lactulose/mannitol ratios compared with uninfected animals (P<0.05). Proinflammatory and ER stress gene expression were activated in the ileum of FIV-infected animals (P<0.05), accompanied by intestinal epithelial damage with loss of epithelial cells and leukocyte infiltration of the lamina propria. Lentivirus infections cause gut inflammation and ensuing damage to intestinal epithelial cells, likely through induction of ER stress pathways, resulting in disruption of gut functional integrity.

Conditional expression of a Gi-coupled receptor in osteoblasts results in trabecular osteopenia

G protein-coupled receptors (GPCRs) coupled to activation of Gs, such as the PTH1 receptor (PTH1R), have long been known to regulate skeletal function and homeostasis. However, the role of GPCRs coupled to other G proteins such as Gi is not well established. We used the tet-off system to regulate the expression of an activated Gi-coupled GPCR (Ro1) in osteoblasts in vivo. Skeletal phenotypes were assessed in mice expressing Ro1 from conception, from late stages of embryogenesis, and after weaning. Long bones were assessed histologically and by microcomputed tomography. Expression of Ro1 from conception resulted in neonatal lethality that was associated with reduced bone mineralization. Expression of Ro1 starting at late embryogenesis resulted in a severe trabecular bone deficit at 12 wk of age (>51% reduction in trabecular bone volume fraction in the proximal tibia compared with sex-matched control littermates; n = 11; P < 0.01). Ro1 expression for 8 wk beginning at 4 wk of age resulted in a more than 20% reduction in trabecular bone volume fraction compared with sex-matched control littermates (n = 16; P < 0.01). Bone histomorphometry revealed that Ro1 expression is associated with reduced rates of bone formation and mineral apposition without a significant change in osteoblast or osteoclast surface. Our results indicate that signaling by a Gi-coupled GPCR in osteoblasts leads to osteopenia resulting from a reduction in trabecular bone formation. The severity of the phenotype is related to the timing and duration of Ro1 expression during growth and development. The skeletal phenotype in Ro1 mice bears some similarity to that produced by knockout of Gs-alpha expression in osteoblasts and thus may be due at least in part to Gi-mediated inhibition of adenylyl cyclase.

Nop53p is a novel nucleolar 60S ribosomal subunit biogenesis protein

Ribosome biogenesis in Saccharomyces cerevisiae occurs primarily in a specialized nuclear compartment termed the nucleolus within which the rRNA genes are transcribed by RNA polymerase I into a large 35 S rRNA precursor. The ensuing association/dissociation and catalytic activity of numerous trans-acting protein factors, RNAs and ribosomal proteins ultimately leads to the maturation of the precursor rRNAs into 25, 5.8 and 18 S rRNAs and the formation of mature cytoplasmic 40 and 60 S ribosomal subunits. Although many components involved in ribosome biogenesis have been identified, our understanding of this essential cellular process remains limited. In the present study we demonstrate a crucial role for the previously uncharacterized nucleolar protein Nop53p (Ypl146p) in ribosome biogenesis. Specifically, Nop53p appears to be most important for biogenesis of the 60 S subunit. It physically interacts with rRNA processing factors, notably Cbf5p and Nop2p, and co-fractionates specifically with pre-60 S particles on sucrose gradients. Deletion or mutations within NOP53 cause significant growth defects and display significant 60 S subunit deficiencies, an imbalance in the 40 S:60 S ratio, as revealed by polysome profiling, and defects in progression beyond the 27 S stage of 25 S rRNA maturation during 60 S biogenesis.

IFN-gamma is an absolute requirement for spontaneous acceptance of liver allografts

Experimental liver allografts undergo spontaneous acceptance despite undergoing rejection during the first few weeks post transplant. We explored the role of interferon-gamma (IFN-gamma) in the spontaneous acceptance of mouse liver allografts. Strain of mouse (CBA) liver allografts transplanted into normal BALB/c mice developed histologic changes typical of rejection that spontaneously regressed, permitting long-term survival of these allografts similar to that of syngeneic grafts. In contrast, CBA liver allografts in IFN-gamma-deficient hosts manifested not only infiltration but also hemorrhage and necrosis, with no survival beyond 14 days. Despite differences in survival, local expression of cytotoxic T-cell genes in the transplant was not increased in IFN-gamma-deficient hosts, but livers in interferon-gamma-deficient mice (GKO) hosts displayed much less induction of major histocompatibility complex (MHC) class I and II expression. To determine whether the difference in survival was secondary to the direct effects of IFN-gamma on the liver, we transplanted livers from IFN-gamma-receptor-deficient mice into normal hosts. Liver allografts lacking IFN-gamma receptors also developed hemorrhage and necrosis with minimal induction of MHC expression. Thus IFN-gamma mediates a direct effect on rejecting liver allografts that reduces hemorrhage and necrosis, induces MHC expression, and is absolutely required for spontaneous acceptance.

The skeletal structure of insulin-like growth factor I-deficient mice

The importance of insulin-like growth factor I (IGF-I) for growth is well established. However, the lack of IGF-I on the skeleton has not been examined thoroughly. Therefore, we analyzed the structural properties of bone from mice rendered IGF-I deficient by homologous recombination (knockout [k/o]) using histomorphometry, peripheral quantitative computerized tomography (pQCT), and microcomputerized tomography (muCT). The k/o mice were 24% the size of their wild-type littermates at the time of study (4 months). The k/o tibias were 28% and L1 vertebrae were 26% the size of wild-type bones. Bone formation rates (BFR) of k/o tibias were 27% that of the wild-type littermates. The k/o bones responded normally to growth hormone (GH; 1.7-fold increase) and supranormally to IGF-I (5.2-fold increase) with respect to BFR. Cortical thickness of the proximal tibia was reduced 17% in the k/o mouse. However, trabecular bone volume (bone volume/total volume [BV/TV]) was increased 23% (male mice) and 88% (female mice) in the k/o mice compared with wild-type controls as a result of increased connectivity, increased number, and decreased spacing of the trabeculae. These changes were either less or not found in L1. Thus, lack of IGF-I leads to the development of a bone structure, which, although smaller, appears more compact.

Microchimerism in sensitized renal patients

BACKGROUND

Patients exposed to allogeneic human tissue sometimes produce anti-HLA antibody for many years in the absence of further obvious antigen exposure. To investigate the mechanism of sustained sensitization, we identified females awaiting renal transplantation with high panel-reactive antibody but no exposure to allogeneic tissue for at least 1 month.

METHODS

We analyzed peripheral blood microchimerism using nested polymerase chain reaction amplification specific for the SRY region of the Y chromosome.

RESULTS

Microchimerism was detected in 3 of 10 patients but in none of 8 normal female subjects. In two cases, the amplified DNA polymerase chain reaction product was sequenced and was confirmed to be identical to the SRY gene. The estimated level of chimerism as compared with serial dilutions of DNA from male peripheral blood leukocytes was about 1/50000.

CONCLUSION

These results do not establish causality but support the possibility that antigens from microchimeric donor cells may sustain the HLA antibody response in certain patients.

Programmed administration of parathyroid hormone increases bone formation and reduces bone loss in hindlimb-unloaded ovariectomized rats

Gonadal insufficiency and reduced mechanical usage are two important risk factors for osteoporosis. The beneficial effects of PTH therapy to reverse the estrogen deficiency-induced bone loss in the laboratory rat are well known, but the influence of mechanical usage in this response has not been established. In this study, the effects of programed administration of PTH on cancellous bone volume and turnover at the proximal tibial metaphysis were determined in hindlimb-unloaded, ovariectomized (OVX), 3-month-old Sprague-Dawley rats. PTH was administered to weight-bearing and hindlimb-unloaded OVX rats with osmotic pumps programed to deliver 20 microg human PTH (approximately 80 microg/kg x day) during a daily 1-h infusion for 7 days. Compared with sham-operated rats, OVX increased longitudinal and radial bone growth, increased indexes of cancellous bone turnover, and resulted in net resorption of cancellous bone. Hindlimb unloading of OVX rats decreased longitudinal and radial bone growth, decreased osteoblast number, increased osteoclast number, and resulted in a further decrease in cancellous bone volume compared with those in weight-bearing OVX rats. Programed administration of PTH had no effect on either radial or longitudinal bone growth in weight-bearing and hindlimb-unloaded OVX rats. PTH treatment had dramatic effects on selected cancellous bone measurements; PTH maintained cancellous bone volume in OVX weight-bearing rats and greatly reduced cancellous bone loss in OVX hindlimb-unloaded rats. In the latter animals, PTH treatment prevented the hindlimb unloading-induced reduction in trabecular thickness, but the hormone was ineffective in preventing either the increase in osteoclast number or the loss of trabecular plates. Importantly, PTH treatment increased the retention of a baseline flurochrome label, osteoblast number, and bone formation in the proximal tibial metaphysis regardless of the level of mechanical usage. These findings demonstrate that programed administration of PTH is effective in increasing osteoblast number and bone formation and has beneficial effects on bone volume in the absence of weight-bearing and gonadal hormones. We conclude that the actions of PTH on cancellous bone are independent of the level of mechanical usage.

Alcohol-induced bone disease: relationship to age and parathyroid hormone levels

Alcohol abuse leads to osteopenia and fractures. Epidemiological evidence suggests that older alcoholics are at substantially greater risk of fractures than younger alcoholics. To examine the interaction of age and alcohol abuse on bone mineral homeostasis, we studied 27 subjects with a history of 10 more years of alcohol abuse ranging in age from 26-68 years. They were evaluated for disordered bone mineral homeostasis by assessing bone density (by quantitative computed tomography of the lumbar spine), histomorphometry of a transcortical biopsy from the iliac crest, serum levels of vitamin D metabolites and parathyroid hormone, and serum and urine levels of bone minerals. Seventeen of the subjects were found to have spinal compression fractures by routine radiologic procedures. The older the subject the more likely the subject was to have such a fracture. Bone densitometry indicated a marked reduction in spinal bone density with 15 subjects below 2 SD of normal aged-matched controls. Bone density fell sharply with the age of the subject. Histomorphometry of iliac crest bone biopsies revealed no evidence of osteomalacia, but total resorption surfaces were increased. Consistent with the lack of osteomalacia were the normal levels of the vitamin D metabolites. The increased total resorption surfaces were correlated with high normal or elevated levels of parathyroid hormone as indicated both by radioimmunoassay and by urinary cAMP levels. Bone formation and active bone resorption (resorption surfaces containing osteoclasts) did not correlate with parathyroid hormone levels, however, but correlated negatively with age.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated 1,25-dihydroxyvitamin D levels in patients with chronic obstructive pulmonary disease treated with prednisone

Glucocorticoid administration is a well established cause of osteopenia. Mechanisms underlying the deleterious effect of glucocorticoids on bone may include direct inhibition of bone formation as well as indirect effects through changes in intestinal calcium absorption, renal calcium excretion, and/or levels of the calciotropic hormones. To further examine the potential role of the calciotropic hormones we measured serum levels of PTH and 1,25 dihydroxyvitamin D [1,25(OH)2D], as well as serum and urine levels of calcium and vertebral bone density in patients with chronic obstructive pulmonary disease being managed with or without prednisone. Patients treated with prednisone had lower spinal bone density (53 vs. 106 mg/cm3) and higher serum calcium (2.40 vs. 2.33 mmol/l), urine calcium (6.9 vs. 2.7 mmol/24h), and 1,25(OH)2D levels (147 vs. 95 pmol/L). Compared to the patients not treated with glucocorticoids. PTH levels also tended to be higher (33 vs. 26 microliters-eq/ml), but the difference was not significant. Serum and urine calcium levels correlated positively with 1,25(OH)2D levels, but none of these measurements correlated with PTH levels. Our results suggest that prednisone treatment alters the regulation of 1,25(OH)2D production, and this may contribute to the loss of bone mineral induced by prednisone.

Set-point for parathyroid hormone release increases with postmaturational aging in the rat

The plasma concentration of immunoreactive PTH (iPTH) increases with postmaturational aging in both humans and animals. In the present study we determined the basal, maximally stimulated, and maximally suppressed levels of iPTH and the concentration of whole blood ionized calcium sufficient to produce half-maximal suppression of the plasma concentration of iPTH (set-point for PTH release) in male Fischer 344 rats aged 3, 6, 12, 18, 24, and 28 months. Basal iPTH increased 2.3-fold from 3 to 28 months of age, whereas basal blood ionized calcium remained unchanged. The set-point for PTH release increased steadily and significantly (P < 0.001) from 1.19 +/- 0.09 mM at 3 months to 1.37 +/- 0.13 mM at 24 months and then declined slightly to 1.32 +/- 0.11 mM at 28 months of age. Basal iPTH correlated significantly with set-point. Neither maximally stimulated nor maximally suppressed iPTH levels showed any significant change with advancing age. These results suggest that the age-related increase in basal plasma iPTH in the rat may be in part a consequence of an increase in the set-point for PTH release.

Kinetics of 1,25-dihydroxyvitamin D metabolism in the aging rat

To determine whether postmaturational aging influences the kinetics of 1,25-dihydroxyvitamin D [1,25(OH)2D] metabolism in the rat, we measured the metabolic clearance (MCR) and production (PR) rates of 1,25(OH)2D in 6-, 12-, 18-, and 24-mo-old Fischer 344 rats using the constant infusion method. Plasma calcium, phosphorus, and parathyroid hormone (PTH), urinary calcium and phosphorus, and glomerular filtration rate (GFR) were also measured. MCR and PR increased 57 and 91%, respectively (when expressed per rat), and 32 and 39%, respectively (when expressed per kg body wt), between 6 and 24 mo of age, with the greatest increase occurring between 18 and 24 mo. The plasma concentration of 1,25(OH)2D remained unchanged. Plasma PTH, when compared with 6-mo-old animals, was significantly elevated at 18 mo (147%) and even higher at 24 mo (240%). GFR (51Cr-labeled EDTA clearance) remained unchanged through 18 mo but tended to be reduced at 24 mo. Plasma phosphorus tended to decrease with age, whereas plasma calcium, urinary calcium, and urinary phosphorus did not differ among the age groups. These data indicate that both clearance and production of 1,25(OH)2D increase with postmaturational aging in the rat. They also suggest that the early age-related rise in plasma PTH is neither a consequence of low plasma calcium nor of renal insufficiency.

1,25-Dihydroxyvitamin D3 and muscle strength in the elderly: a randomized controlled trial

An unexplained loss of muscle strength occurs with aging. Vitamin D deficiency can cause myopathy and administration of 1,25-dihydroxyvitamin D3 [1,25-(OH2)D3] to persons with low serum concentrations can improve strength. To test the hypothesis that the weakness associated with aging is in part due to inadequate serum concentrations of [1,25-(OH2)D3], we conducted a randomized, controlled, double blinded trial in 98 men and women volunteers over 69 yr old. Treatment consisted of 0.25 micrograms 1,25-(OH)2D3, orally, twice per day or identical placebo for 6 months. Leg muscle strength of the quadriceps was measured with an isokinetic dynamometer. There was no difference between the two groups at 1 week, 1 month, or 6 months of treatment in any of the measures of muscle strength. We conclude that oral administration of 0.5 micrograms 1,25-(OH)2D3/day does not improve muscle strength in older persons. Further research is needed to determine the etiology of the decline in muscle strength associated with aging.

Assessment of the free fraction of 25-hydroxyvitamin D in serum and its regulation by albumin and the vitamin D-binding protein

We measured the free fraction of 25-hydroxyvitamin D (25OHD) in human serum and determined that 25OHD bound to a component with an affinity constant of 7 X 10(8) M-1 and a concentration of 4.5 X 10(-6) M. This concentration was equal to that of the vitamin D-binding protein (DBP) in the same serum sample. We removed DBP from the serum using actin affinity columns and found that the affinity for 25OHD of the remaining serum components was equivalent to that of human serum albumin (6 X 10(5) M-1). We then measured the free fractions of 25OHD, DBP, and albumin in normal and cirrhotic subjects. We calculated that 88 +/- 3% (+/- SD) and 83 +/- 8% of the 25OHD were bound to DBP in the serum of normal and cirrhotic subjects, respectively. We compared previously reported data for the free fraction and the free concentration of 1,25-dihydroxyvitamin D in these subjects with the current data for the free fraction and free concentration of 25OHD. The total concentrations and free fractions of both metabolites correlated to each other and to the DBP and albumin concentrations in these subjects, but the free concentrations of these metabolites did not. We conclude that 25OHD, like 1,25-dihydroxyvitamin D, is transported in blood bound primarily to DBP and albumin. Changes in the concentrations of DBP and albumin affected the total and free fractions of 25OHD in serum, but the actual free concentration of 25OHD was independent of such changes.

Skeletal response to dietary calcium in a rat model simulating weightlessness

Unweighting the hindlimbs of a rat by tail suspension leads to a decrease in bone in the unweighted hindlimbs, but not in the normally weighted forelimbs. We evaluated whether increments in dietary calcium could prevent this. Growing rats were fed diets ranging in calcium content from 0.1% to 2.4%. After the rats were suspended for two weeks, we found no differences between suspended and control animals fed the same diet with respect to calcium transport or serum levels of calcium, phosphorus, 1,25-dihydroxyvitamin D, and parathyroid hormone. In both groups, increasing dietary calcium reduced active intestinal calcium transport and serum 1,25-dihydroxyvitamin D levels. The calcium content of the tibia and lumbar vertebra (but not the humerus) was reduced in suspended rats compared to control rats fed the same diet. However, increasing dietary calcium increased the calcium content of all bones in both suspended and control animals. The bone formation rate at the tibiofibular junction (measured by double-label tetracycline) was reduced in the suspended animals compared to controls and was not altered by dietary calcium. However, the marrow area of the tibia, an indication of bone resorption, did not differ between suspended and control animals and was equally reduced in both groups when dietary calcium was increased. Our data suggest that the deleterious effects of skeletal unweighting on bone formation cannot be explained by changes in the calciotropic hormones and are not reversed by increments in dietary calcium. However, increasing dietary calcium can increase bone calcium, even in unweighted limbs, by decreasing bone resorption.

Free 1,25-dihydroxyvitamin D levels in serum from normal subjects, pregnant subjects, and subjects with liver disease

We measured the free concentration of 1,25-dihydroxyvitamin D (1,25[OH]2D) using centrifugal ultrafiltration, and the level of vitamin D-binding protein (DBP) in 24 normal subjects, 17 pregnant subjects, and 25 alcoholic subjects with liver disease. Our objective was to determine whether the increase in total 1,25(OH)2D levels in pregnant women and the reduction in total 1,25(OH)2D levels in subjects with liver disease reflected a true difference in free 1,25(OH)2D levels or whether such differences were due solely to the variations in DBP levels (and thus, the amount of 1,25[OH]2D bound) in these groups. In subjects with liver disease the mean total 1,25(OH)2D concentration (22.6 +/- 12.5 pg/ml) and the mean DBP concentration (188 +/- 105 micrograms/dl) were nearly half the normal values (41.5 +/- 11.5 pg/ml and 404 +/- 124 micrograms/dl, respectively, P less than 0.001), whereas the mean free 1,25(OH)2D level was similar to normal values (209 +/- 91 fg/ml and 174 +/- 46 fg/ml, respectively). In contrast, in pregnant subjects the mean total 1,25(OH)2D level (82 +/- 21 pg/ml) and mean DBP level (576 +/- 128 micrograms/dl) were significantly higher than normal (P less than 0.001). Although the mean percent free 1,25(OH)2D level in pregnant subjects was below normal (0.359 +/- 0.07% vs. 0.424 +/- 0.07%, P less than 0.001), the mean free 1,25(OH)2D level was 69% higher than normal (294 +/- 98 fg/ml vs. 174 +/- 46 fg/ml, P less than 0.001). When data from all three groups were combined, there was a linear correlation between total 1,25(OH)2D and DBP levels but not between DBP and percent free 1,25(OH)2D levels; the increased DBP levels in the pregnant subjects were associated with less of an effect on percent free 1,25(OH)2D than were the reduced DBP levels in the subjects with liver disease. Our data suggest that (a) free 1,25(OH)2D levels appear to be well maintained even in subjects with liver disease and reduced DBP levels, (b) free 1,25(OH)2D levels are increased during pregnancy despite the increase in DBP levels, and (c) free 1,25(OH)2D levels cannot be inferred accurately from measurements of total 1,25(OH)2D and DBP levels alone in subjects with various physiologic and pathophysiologic conditions.

Metabolic alkalosis in models of primary and secondary hyperparathyroid states

Hyperchloremic metabolic acidosis has been reported in clinical states of primary and secondary hyperparathyroidism (HPT). Acute administration of parathyroid hormone (PTH) decreases renal acidification in humans and dogs, but the renal and systemic acid-base effects of chronic HPT have not been extensively investigated. In chronically thyroparathyroidectomized (TPTX) dogs (group I), bPTH 1-5 U/kg twice daily resulted in sustained hypophosphatemia, hypercalcemia, and Cl- -resistant metabolic alkalosis that was of renal origin at least in part: delta [HCO3-]p + 4.1 +/- 0.8 meq/liter, P less than 0.01; delta [H+]p -4 +/- 1 neq/liter, P less than 0.001, days 10-12. The cumulative change (sigma delta) in net acid excretion (NAE) was +44 meq (day 9, P less than 0.05). Similarly, metabolic alkalosis of renal origin, at least in part, occurred when PTH was administered by chronic continuous intravenous infusion (group II). Since chronic administration of calcitriol in dogs results in metabolic alkalosis, plasma calcitriol concentration was measured and found not to be increased by chronic intravenous PTH administration. In intact dogs (group III), a continuous chronic intravenous infusion of the Ca2+ chelator, Na4EGTA (3.0 mmol/kg daily), substituted for an equimolar amount of prechelated EGTA (CaNa2EGTA), resulted in a model of hypocalcemic HPT and severe Cl- -resistant metabolic alkalosis: delta [HCO3-]p +9.1 +/- 1.9 meq/liter, P less than 0.05; delta [H+]p -5 +/- 1 neq/liter, P less than 0.01, days 6-8. NAE decreased significantly. Thus, whereas metabolic alkalosis induced by PTH administration could be accounted for by increased NAE (group I), EGTA-induced metabolic alkalosis was accounted for by an extrarenal mechanism of base input to extracellular fluid (group III). Neutralization of the extrarenal base input by chronic administration of HCl during the period of EGTA-induced HPT did not preclude the development of metabolic alkalosis (group V), suggesting that a renal component was present in EGTA-induced metabolic alkalosis as well as in models of primary HPT (groups I and II). During the steady state, in this group as in the groups administered PTH, the net endogenous load of acid to the systemic circulation requiring renal excretion was unchanged from control, as indicated by stable values of NAE not significantly different from control. Yet metabolic alkalosis persisted in the steady state.(ABSTRACT TRUNCATED AT 400 WORDS)