Kidney biopsy for the diagnosis and treatment of kidney diseases. Recommendations from the French speaking Society of Nephrology (SFNDT) and French National Authority for Health (HAS) 2022

Kidney Biopsy (KB) is a crucial diagnostic tool in the field of renal diseases and is routinely performed in nephrology departments. A previous survey conducted by the Société Francophone de Néphrologie Dialyse Transplantation (SFNDT) revealed significant disparities in clinical practices, sometimes conflicting with the existing literature and recently published recommendations. In response, the SFNDT wished to promote the development of best practice guidelines, under the auspices of the French National Authority for Health (HAS), to establish a standardized framework for performing kidney biopsies in France.

Glomerular filtration rate estimation in adults: myths and promises

BACKGROUND

In daily practice, glomerular filtration rate (GFR) is estimated with equations including renal biomarkers. Among these biomarkers, serum creatinine remains the most used. However, there are many limitations with serum creatinine we will discuss in the current review. We will also discuss how creatinine-based equations have been developed and what we can expect from them in terms of performance to estimate GFR.

SUMMARY

Different creatinine-based equations have been proposed. We will show the advantages of the recent European Kidney Function Consortium (EKFC) equation. This equation can be used in children and adults. This equation can also be used with some flexibility in different populations.

KEY MESSAGES

GFR is estimated by creatinine-based equations, but the most important for nephrologists is probably to know the limitations of these equations.

Glomerular Filtration Rate Measured Based on Iomeprol Clearance Assessed at CT Urography in Living Kidney Donor Candidates

Background Estimating glomerular filtration rate (GFR) from serum creatinine can be inaccurate, and current procedures for measuring GFR are time-consuming and cumbersome. Purpose To develop a method for measuring GFR based on iomeprol clearance assessed at CT urography in kidney donor candidates and compare this with iohexol clearance (reference standard for measuring GFR). Materials and Methods This cross-sectional retrospective study included data from kidney donor candidates who underwent both iohexol clearance and CT urography between July 2016 and October 2022. CT-measured GFR was calculated as the iomeprol excretion rate in the urinary system between arterial and excretory phases (Hounsfield units times milliliters per minute) divided by a surrogate for serum iomeprol concentration in the aorta at the midpoint (in Hounsfield units). Performance of CT-measured GFR was assessed with use of mean bias (mean difference between CT-measured GFR and iohexol clearance), precision (the distance between quartile 1 and quartile 3 of the bias [quartile 3 minus quartile 1], with a small value indicating high precision), and accuracy (percentage of CT-measured GFR values falling within 10%, 20%, and 30% of iohexol clearance values). Intraobserver agreement was assessed for 30 randomly selected individuals with the Lin concordance correlation coefficient. Results A total of 75 kidney donor candidates were included (mean age, 51 years ± 13 [SD]; 45 female). The CT-measured GFR was unbiased (1.1 mL/min/1.73 m2 [95% CI: -1.9, 4.1]) and highly precise (16.2 mL/min/1.73 m2 [quartiles 1 to 3, -6.6 to 9.6]). The accuracy of CT-measured GFR within 10%, 20%, and 30% was 61.3% (95% CI: 50.3, 72.4), 88.0% (95% CI: 80.7, 95.4), and 100%, respectively. Concordance between CT-based GFR measurements taken 2 months apart was almost perfect (correlation coefficient, 0.99 [95% CI: 0.98, 0.99]). Conclusion In living kidney donors, GFR measured based on iomeprol clearance assessed at CT urography showed good agreement with GFR measured based on iohexol clearance. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Davenport in this issue.

Diagnostic standard: assessing glomerular filtration rate

Creatinine-based estimated GFR (eGFR) is imprecise at individual level, due to non-GFR-related serum creatinine determinants, including atypical muscle mass. Cystatin C has the advantage of being independent on muscle mass, a feature that led to the development of race- and sex-free equations. Yet, cystatin C-based equations do not perform better than creatinine-based equations to estimate GFR, unless both variables are included together. The new race-free Chronic Kidney Disease Epidemiology (CKD-EPI) equation, had slight opposite biases between Black and Non-Black subjects in USA, but performs poorer than that the previous version in European populations. The European Kidney Function Consortium (EKFC) equation developed in 2021 can be used both in children and adults, is more accurate in young and old adults, and is applicable to non-white European populations, by rescaling the Q factor, i.e. population median creatinine, in a potentially universal way. A sex- and race-free cystatin C-based EKFC, with the same mathematical design, has also be defined. New developments in the field of GFR estimation would be standardization of cystatin C assays, development of creatinine-based eGFR equations that would incorporate muscle mass data, implementation of new endogenous biomarkers, and the use of artificial intelligence. Standardization of different GFR measurement methods would also be a future challenge, as well as new technologies for measuring GFR. Future research is also needed on discrepancies between cystatin C and creatinine, which is associated with high risk of adverse events: standardize the definition of discrepancy, and understand its determinants.

New and old GFR equations: a European perspective

Glomerular filtration rate (GFR) is estimated in clinical practice from equations based on the serum concentration of endogenous biomarkers and demographic data. The 2009 creatinine-based Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI2009) was recommended worldwide until 2021, when it was recalibrated to remove the African-American race factor. The CKD-EPI2009 and CKD-EPIcr2021 equations overestimate GFR of adults aged 18-30 years, with a strong overestimation in estimated GFR (eGFR) at age 18 years. CKD-EPICr2021 does not perform better than CKD-EPI2009 in US population, overestimating GFR in non-Black subjects, and underestimating it in Black subjects with the same magnitude. CKD-EPICr2021 performed worse than the CKD-EPI2009 in White Europeans, and provides no or limited performance gains in Black European and Black African populations. The European Kidney Function Consortium (EKFC) equation, which incorporates median normal value of serum creatinine in healthy population, overcomes the limitations of the CKD-EPI equations: it provides a continuity of eGFR at the transition between pediatric and adult care, and performs reasonably well in diverse populations, assuming dedicated scaling of serum creatinine (Q) values is used. The new EKFC equation based on cystatin C (EKFCCC) shares the same mathematical construction, namely, it incorporates the median cystatin C value in the general population, which is independent of sex and ethnicity. EKFCCC is therefore a sex-free and race-free equation, which performs better than the CKD-EPI equation based on cystatin C. Despite advances in the field of GFR estimation, no equation is perfectly accurate, and GFR measurement by exogenous tracer clearance is still required in specific populations and/or specific clinical situations.

Development and validation of a new equation based on plasma creatinine and muscle mass assessed by CT scan to estimate glomerular filtration rate: a cross-sectional study

Background

Inter-individual variations of non-glomerular filtration rate (GFR) determinants of serum creatinine, such as muscle mass, account for the imperfect performance of estimated GFR (eGFR) equations. We aimed to develop an equation based on creatinine and total lumbar muscle cross-sectional area measured by unenhanced computed tomography scan at the third lumbar vertebra.

Methods

The muscle mass-based eGFR (MMB-eGFR) equation was developed in 118 kidney donor candidates (iohexol clearance) using linear regression. Validation cohorts included 114 healthy subjects from another center (⁵¹Cr-EDTA clearance, validation population 1), 55 patients with chronic diseases (iohexol, validation population 2), and 60 patients with highly discordant creatinine and cystatin C-based eGFR, thus presumed to have atypical non-GFR determinants of creatinine (⁵¹Cr-EDTA, validation population 3). Mean bias was the mean difference between eGFR and measured GFR, precision the standard deviation (SD) of the bias, and accuracy the percentage of eGFR values falling within 20% and 30% of measured GFR.

Results

In validation population 1, performance of MMB-eGFR was not different from those of CKD-EPI_Cr2009 and CKD-EPI_Cr2021. In validation population 2, MMB-eGFR was unbiased and displayed better precision than CKD-EPI_Cr2009, CKD-EPI_Cr2021 and EKFC (SD of the biases: 13.1 vs 16.5, 16.8 and 15.9 mL/min/1.73 m²). In validation population 3, MMB-eGFR had better precision and accuracy {accuracy within 30%: 75.0% [95% confidence interval (CI) 64.0-86.0] vs 51.5% (95% CI 39.0-64.3) for CKD-EPI_Cr2009, 43.3% (95% CI 31.0-55.9) for CKD-EPICr2021, and 53.3% (95% CI 40.7-66.0) for EKFC}. Difference in bias between Black and white subjects was -2.1 mL/min/1.73 m² (95% CI -7.2 to 3.0), vs -8.4 mL/min/1.73 m² (95% CI -13.2 to -3.6) for CKD-EPI_Cr2021.

Conclusion

MMB-eGFR displayed better performances than equations based on demographics, and could be applied to subjects of various ethnic backgrounds.

Natural course and determinants of short-term kidney function decline in hereditary transthyretin amyloidosis: a French observational study

Data regarding renal involvement in patients with hereditary transthyretin (ATTRv) amyloidosis are scarce and the natural course of chronic kidney disease (CKD) in this population remains unclear. This observational study, including adult patients diagnosed with ATTRv amyloidosis at the French Reference Centre for Cardiac Amyloidosis, investigated renal function outcome and its determinants. Multivariable logistic regression models identified factors associated with CKD at baseline. Determinants of the change in estimated glomerular filtration rate (eGFR) over 24 months of follow-up were assessed with a multivariable linear mixed-effects model. In total, 232 patients (78 women [34%], mean age: 64 years) with ATTRv amyloidosis were classified on the basis of their TTR variants: ATTRV122I (37%), ATTRV30M (29%), and other variants (34%). Median baseline eGFR was 78 ml/min/1.73 m². Seventy-two patients (31%) had an eGFR below 60 ml/min/1.73m² and 27/137 patients (20%) had significant proteinuria (urine protein/creatinine ratio ≥30 mg/mmol). Renal biopsy, performed in four cases, found typical Congo red-positive and TTR-labelled amyloid deposits in all cases. Older age (OR 1.07, p < .001) and a prior history of hypertension (OR 2.09, p = .04) were associated with a higher prevalence of CKD at baseline, whereas higher left ventricular global longitudinal strain (LVGLS) (OR 0.83, p < .001) was associated with a lower prevalence. The estimated change in eGFR was -7.12 [-9.61, -4.63] and -8.21 [-10.81, -5.60] ml/min/1.73 m² after 12 and 24 months of follow-up, respectively. eGFR decline was independently associated with older age ((67-74], coefficient= -14.35 mL/min/1.73 m², p < .01, >74, coefficient = -22.93 mL/min/1.73 m², p < .001, versus <56), ATTRV122I (coefficient = -17.17 mL/min/1.73m², p < .01, versus ATTRV30M) and LVGLS (coefficient = 1.22, p < .01). These data suggest that CKD is a common finding in patients with ATTRv amyloidosis, and that eGFR decline is rapid during the first year of evaluation. Older age, lower LVGLS and ATTRV122I were associated with a worse renal outcome. Further studies are now needed to evaluate effects of new targeted therapies on long term renal function.

Performance of creatinine-based equations to estimate glomerular filtration rate in White and Black populations in Europe, Brazil and Africa

BACKGROUND

A new Chronic Kidney Disease Epidemiology Collaboration equation without the race variable has been recently proposed (CKD-EPIAS). This equation has neither been validated outside USA nor compared with the new European Kidney Function Consortium (EKFC) and Lund-Malmö Revised (LMREV) equations, developed in European cohorts.

METHODS

Standardized creatinine and measured glomerular filtration rate (GFR) from the European EKFC cohorts (n = 13 856 including 6031 individuals in the external validation cohort), from France (n = 4429, including 964 Black Europeans), from Brazil (n = 100) and from Africa (n = 508) were used to test the performances of the equations. A matched analysis between White Europeans and Black Africans or Black Europeans was performed.

RESULTS

In White Europeans (n = 9496), both the EKFC and LMREV equations outperformed CKD-EPIAS (bias of -0.6 and -3.2, respectively versus 5.0 mL/min/1.73 m², and accuracy within 30% of 86.9 and 87.4, respectively, versus 80.9%). In Black Europeans and Black Africans, the best performance was observed with the EKFC equation using a specific Q-value (= concentration of serum creatinine in healthy males and females). These results were confirmed in matched analyses, which showed that serum creatinine concentrations were different in White Europeans, Black Europeans and Black Africans for the same measured GFR, age, sex and body mass index. Creatinine differences were more relevant in males.

CONCLUSION

In a European and African cohort, the performances of CKD-EPIAS remain suboptimal. The EKFC equation, using usual or dedicated population-specific Q-values, presents the best performance in the whole age range in the European and African populations included in this study.

MO385: Performance of Creatinine-Based Equations to Estimate Glomerular Filtration Rate in White and Black Subjects From Europe, Brazil and Africa

BACKGROUND AND AIMS

Current Glomerular filtration rate (GFR) estimating equations based on serum creatinine are facing increased criticism due to the inclusion of a race correction in black Americans with the CKD-EPI equation (CKD-EPIASR, A = Age, S = Sex, R = Race). A new equation without race (CKD-EPIAS) has been proposed. However, this equation was developed mainly from US cohorts. The performance of this new equation has been poorly compared with current European-developed creatinine-based equations, i.e. the Lund-Malmö Revised (LMR), and the new European Kidney Function Consortium (EKFC)

METHOD

Data from subjects over 18 years, representing 11 cohorts from Europe (previously described as the EKFC dataset, n = 13 856), and enhanced with data from Brazil (n = 100), France (n = 4429) and Africa [Democratic Republic of Congo (DRC) and Côte d'Ivoire, n = 508] were considered (n = 18 893 for the whole cohort). The EKFC cohort was considered as non-black population. All data from Africa derived from black individuals. From France, 964 subjects were self-reported as black (=Blacks from Paris). Measured GFR as a reference method and IDMS creatinine results were available. Median bias (eGFR—mGFR) with 95% confidence intervals (CI), imprecision (interquartile range: IQR), and P30 accuracy (percentage of eGFR-values within ± 30% of mGFR) with 95% CI were calculated.

RESULTS

Results are summarized in Table.

CONCLUSION

The new CKD-EPIAS has been launched in the USA for societal reasons and is now recommended by US guidelines. However, in Europe and Africa, its performance was suboptimal. The EKFC equation, using the usual Q values, or population-specific Q values (when available), displays the best performance over the whole age range for populations in Europe and Africa.

Myosteatosis as an independent risk factor for mortality after kidney allograft transplantation: a retrospective cohort study

BACKGROUND

Patients with end-stage renal disease may display both a loss of skeletal muscle mass and an increase in muscle fat deposits. We aimed to analyse the impact of low skeletal muscle mass index (SMI, surrogate marker of sarcopenia) and low muscle density (MD, surrogate marker of myosteatosis) on patient survival after kidney transplantation (KT).

METHODS

In a retrospective cohort of 200 kidney transplant recipients (KTr), we measured on an unenhanced cross-sectional computed tomography scan taken at the level of the third lumbar vertebra within the previous year or at the time of KT, both SMI (muscle cross-sectional area normalized for height² , reported in cm² /m² ) and MD (mean attenuation of muscle cross-sectional area, expressed in Hounsfield units). We determined age-specific and sex-specific normality thresholds on 130 healthy subjects. The baseline factors associated with low MD were assessed by logistic regression analysis. Cox proportional hazard univariable and multivariable models were constructed to identify predictive factors of patient survival.

RESULTS

Among the 200 patients of the cohort, 123 were male (62%), and mean age was 54.8 ± 13.8 years. A total of 181 KTr required renal replacement therapy before KT (91%), and 36 KTr (18%) received repeat kidney transplant after previous failed KT. Mean MD was 30.6 ± 9 HU in men and 29.7 ± 8.3 HU in women, whereas SMI was 49.7 ± 8.6 cm² /m² in men and 42.3 ± 7.3 cm² /m² in women. MD was below the 2.5th percentile for the healthy population in 49 KTr (25%), defining the myosteatosis group, while SMI was below the 2.5th percentile for the reference population in 10 KTr (5%). Independent risk factors for myosteatosis were two or more KT [adjusted odds ratio (aOR) 5.2, 95% confidence interval (95% CI): 2.22-12.4, P = 0.0001], a history of stroke (aOR 3.7, 95% CI: 1.30-10.7, P = 0.015), and body mass index > 25 kg/m² (aOR 2.94, 95% CI: 1.4-6.18, P = 0.004). Myosteatosis was independently associated with mortality [adjusted hazard ratio (aHR) 2.12, 95% CI: 1.06-4.24, P = 0.033], as were cardiovascular disease (HR 2.06, 95% CI: 1.02-4.15, P = 0.043) and age (aHR 1.06, 95% CI: 1.03-1.09, P = 0.0003). Low SMI was not associated with mortality.

CONCLUSIONS

Myosteatosis, which was more prevalent than low skeletal muscle mass, might be an important prognostic marker in patients undergoing KT.

Impact of pre-eclampsia on renal outcome in sickle cell disease patients

The long-term consequences of pre-eclampsia (PrE) for renal function have never been determined in patients with sickle cell disease (SCD). Between 2008 and 2015, we screened 306 pregnancies in women with SCD and identified 40 with PrE (13%). The control group consisted of 65 pregnant SCD patients without PrE. In multivariable analysis, PrE events were associated with an increase of 1 log of lactate dehydrogenase level (adjusted odds ratio, aOR = 3·83, P = 0·05), a decrease of 10 g/l of haemoglobin levels (aOR = 2·48, P = 0·006) and one or more vaso-occlusive crisis during pregnancy (aOR = 16·68, P = 0·002). Estimated glomerular filtration rate (eGFR) was similar in the two groups at steady state but was significantly lower in the PrE group after one year of follow-up and at last follow-up (130 vs 148 ml/min/1·73 m² , P < 0·001 and 120 vs 130 ml/min/1·73 m² , P < 0·001, respectively). In multivariable analysis, eGFR had returned to steady-state levels one year after pregnancy in patients without PrE but continued to decrease in patients with PrE (β = -18·15 ml/min/1·73 m² , P < 0·001). This decline was more marked at the end of follow-up (β = -31·15 ml/min, P < 0·001). In conclusion, PrE episodes are associated with a significant risk of subsequent renal function decline in SCD patients.

Impact of renal function on hydroxyurea exposure in sickle-cell disease patients

AIMS

This prospective study aimed to develop a population pharmacokinetics (PK) model of hydroxyurea (HU) in patients with sickle cell disease. This model can be used to determine the impact of glomerular filtration rate (GFR) on HU kinetics.

METHODS

We included 30 patients. They underwent HU pharmacokinetics analyses of plasma and urine. Six underwent PK analyses in 2 periods with and without angiotensin-converting enzyme inhibitor. HU was assayed with a validated high-performance liquid chromatography-UV method. Noncompartmental PK analysis was conducted and a population PK model built with Monolix. This model was validated externally on another 56 patients. HU PK was simulated as a function of GFR.

RESULTS

The HU PK model was constructed as a 2-compartment model with first-order absorption and elimination. The quality criteria were good, including for external validation. We found that estimated GFR (eGFR) and body weight affected HU PK, with lower eGFR or body weight associated with a higher HU area under the curve. We recommend the monitoring of HU through eGFR and body weight, which together account for 47% of its variability. Urinary HU fractions and renal clearance were higher in the glomerular hyperfiltration group and lower in the moderate chronic kidney disease group, respectively. No differences in nonrenal HU clearance were observed.

CONCLUSION

Estimated GFR has an impact on the kinetics of hydroxyurea, and HU dose should be adapted accordingly. Angiotensin-converting enzyme inhibitor seems to have minor effect on HU PK in adults with sickle cell disease.

Encrusted Urinary Tract Infections Due to Corynebacteria Species

Introduction

Encrusted pyelitis and cystitis are peculiar disorders characterized by the calcification of the vesical, the pyelic, and/or the ureteral walls. These calcifications are composed of struvite and calcium carbonate‒apatite due to the presence of Corynebacterium urealyticum.

Methods

We have identified the clinical features and outcomes of 17 patients with encrusted pyelitis (n = 15) or encrusted cystitis (n = 2). Diagnosis was based on computed tomography scan and sonography including thickening and calcified lesions of the urinary tract.

Results

The main clinical presentation was suggestive of subacute urinary tract infection with fever and urologic symptoms, mostly gross hematuria. Biologic features were characterized by the presence of struvite crystals and alkaline urine. Acute kidney injury was reported in 70.6% of cases. Predisposing factors were mostly due to urologic background (82.4%) with a history of urologic procedure (71%) and prior exposure to antibiotics (59%). All patients received appropriate antibiotherapy and 15 were treated with topical urinary acidification. A significant reduction of encrusted calcifications was observed in 88% of cases. Renal function improved in 71% of the patients. Nevertheless, poor tolerance of the treatment and side effects were common, affecting 71% of patients, with Gram-negative bacilli urinary tract infections (53%) being the most frequent. At last follow-up, 4 patients (23.5%) progressed to end-stage renal disease and only 1 had a clinical relapse.

Conclusions

Encrusted urinary tract infections are rare, characterized by a severe renal and overall prognosis in the absence of appropriate treatment. Topical urinary acidification and appropriate antibiotherapy are efficient but may be burdened by significant adverse events.

Tubular Acidification Defect in Adults with Sickle Cell Disease

BACKGROUND AND OBJECTIVES

Metabolic acidosis is a frequent manifestation of sickle cell disease but the mechanisms and determinants of this disorder are unknown. Our aim was to characterize urinary acidification capacity in adults with sickle cell disease and to identify potential factors associated with decreased capacity to acidify urine.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 25 adults with sickle cell disease and an eGFR of ≥60 ml/min per 1.73 m² from a single center in France, we performed an acute acidification test after simultaneous administration of furosemide and fludrocortisone. A normal response was defined as a decrease in urinary pH <5.3 and an increase in urinary ammonium excretion ≥33 µEq/min at one or more of the six time points after furosemide and fludrocortisone administration.

RESULTS

Of the participants (median [interquartile range] age of 36 [24-43] years old, 17 women), 12 had a normal and 13 had an abnormal response to the test. Among these 13 participants, nine had normal baseline plasma bicarbonate concentration. Plasma aldosterone was within the normal range for all 13 participants with an abnormal response, making the diagnosis of type 4 tubular acidosis unlikely. The participants with an abnormal response to the test were significantly older, more frequently treated with oral bicarbonate, had a higher plasma uric acid concentration, higher hemolysis activity, lower eGFR, lower baseline plasma bicarbonate concentration, higher urine pH, lower urine ammonium ion excretion, and lower fasting urine osmolality than those with a normal response. Considering both groups, the maximum urinary ammonium ion excretion was positively correlated with fasting urine osmolality (r ²=0.34, P=0.002), suggesting that participants with sickle cell disease and lower urine concentration capacity have lower urine acidification capacity.

CONCLUSIONS

Among adults with sickle cell disease, impaired urinary acidification capacity attributable to distal tubular dysfunction is common and associated with the severity of hyposthenuria.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_12_10_CJN07830719.mp3.

Human Apoptotic Cells, Generated by Extracorporeal Photopheresis, Modulate Allogeneic Immune Response

The induction of specific and sustainable tolerance is a challenging issue in organ transplantation. The discovery of the immunosuppressive properties of apoptotic cells in animal models has paved the way for their use in human transplantation. In this work, we aimed to define a stable, reproducible, and clinically compatible production procedure of human apoptotic cells (Apo-cells). Using a clinically approved extracorporeal photopheresis technique, we have produced and characterized phenotypically and functionally human apoptotic cells. These Apo-cells have immunosuppressive properties proved in vitro and in vivo in NOD/SCID/γC mice by their capacity to modulate an allogeneic response following both a direct and an indirect antigen presentation. These results brought the rationale for the use of Apo-cells in tolerance induction protocol for organ transplantation.

Creatinine clearance after cimetidine administration in a new short procedure: comparison with plasma and renal clearances of iohexol

Background

Creatinine clearance after cimetidine administration (Cim-CreatClr) was once proposed as a method of glomerular filtration rate (GFR) measurement, but has been largely abandoned. We investigated whether a new short procedure for Cim-CreatClr determination could be considered an appropriate method for GFR measurement.

Methods

A 150-min protocol involving oral cimetidine administration was developed to determine Cim-CreatClr. In total, 168 patients underwent simultaneous assessments of creatinine clearance before and after cimetidine administration [basal creatinine clearance (Basal-CreatClr) and Cim-CreatClr, respectively], renal iohexol clearance and plasma iohexol clearance (R-iohexClr and P-iohexClr, respectively). We compared the agreement between the various methods of GFR measurement, using Bland–Altman plots to determine biases, precisions (standard deviation of the biases) and accuracy (proportions of GFR values falling within 10, 15 and 30% of the mean: P10, P15 and P30, respectively).

Results

After cimetidine administration, Basal-CreatClr decreased by 19.8% [95% reference limits of agreement (95% LoA): −2.2 to 41.7%]. The bias between Cim-CreatClr and P-iohexClr was −0.6% (95% LoA −26.8 to 28%); the precision was 14.0%; P10, P15 and P30 were 57.1% [95% confidence interval (95% CI) 49.3 to 64.7%], 73.2% (95% CI 65.8 to 79.7%) and 97.0% (95% CI 93.2 to 99.0%), respectively. Due to the positive bias (16.7%; 95% LoA −3.6 to 36.9%) of Cim-CreatClr relative to R-iohexClr, accuracy of Cim-CreatClr relative to R-iohexClr was poor despite a good precision (10.3%).

Conclusions

Our study shows a high level of agreement between Cim-CreatClr and P-iohexClr. These results suggest that this short Cim-CreatClr procedure is a valid method for GFR measurement, which might be useful, in particular, in situations in which P-iohexClr is not suitable or not available.

Epidemiology, Risk Factors, and Outcomes of Opportunistic Infections after Kidney Allograft Transplantation in the Era of Modern Immunosuppression: A Monocentric Cohort Study

Epidemiology of opportunistic infections (OI) after kidney allograft transplantation in the modern era of immunosuppression and the use of OI prevention strategies are poorly described. We retrospectively analyzed a single-center cohort on kidney allograft adult recipients transplanted between January 2008 and December 2013. The control group included all kidney recipients transplanted in the same period, but with no OI. We analyzed 538 kidney transplantations (538 patients). The proportion of OI was 15% (80 and 72 patients). OI occurred 12.8 (6.0–31.2) months after transplantation. Viruses were the leading cause (n = 54, (10%)), followed by fungal (n = 15 (3%)), parasitic (n = 6 (1%)), and bacterial (n = 5 (0.9%)) infections. Independent risk factors for OI were extended criteria donor (2.53 (1.48–4.31), p = 0.0007) and BK viremia (6.38 (3.62–11.23), p < 0.0001). High blood lymphocyte count at the time of transplantation was an independent protective factor (0.60 (0.38–0.94), p = 0.026). OI was an independent risk factor for allograft loss (2.53 (1.29–4.95), p = 0.007) but not for patient survival. Post-kidney transplantation OIs were mostly viral and occurred beyond one year after transplantation. Pre-transplantation lymphopenia and extended criteria donor are independent risk factors for OI, unlike induction therapy, hence the need to adjust immunosuppressive regimens to such transplant candidates.

Sickle cell disease and albuminuria: recent advances in our understanding of sickle cell nephropathy

Albuminuria is considered to be a relevant biomarker for the detection of early glomerular damage in patients with sickle cell disease (SCD). Improvements in our understanding of the pathophysiological processes and molecular mechanisms underlying albuminuria are required, because increasing numbers of patients with SCD are developing chronic kidney disease. The early recognition of sickle cell nephropathy (SCN) and studies of the natural course of this emerging renal disease are therefore crucial, together with identification of the associated clinical and biological risk factors, to make it possible to initiate kidney-protective therapy at early stages of renal impairment. The pathophysiological process underlying SCN remains hypothetical, but chronic haemolysis-related endothelial dysfunction and the relative renal hypoxia triggered by repeated vaso-occlusive crises have been identified as two potential key factors. The optimal preventive and curative management of albuminuria in the context of SCD is yet to be established, but recent studies have suggested that hydroxyurea therapy, the cornerstone of SCD treatment, could play a key role in reducing albuminuria. The place of conventional kidney-protecting measures, such as renin–angiotensin system inhibitors, in the treatment of SCD patients also remains to be determined.

Loss of tubular creatinine secretion as the only sign of tubular proximal cell dysfunction in light chain proximal tubulopathy: A case report

Light chain proximal tubulopathy (LCPT) is a rare disease, characterized by cytoplasmic inclusions of light chain (usually kappa) immunoglobulins. Clinical presentation is usually a Fanconi syndrome. The proximal tubular dysfunction can be incomplete, and exceptional cases of LCPT without any tubular dysfunction have even been described. Here, we report a case of LCPT in which the only sign of proximal tubulopathy is the absence of secretion of creatinine, as assessed by the simultaneous measurement of renal clearance of creatinine and CrEDTA. The loss of tubular creatinine secretion as a sign of tubular proximal cell dysfunction ought to be identified in patients with light chain proximal tubulopathy as it leads to a clinically relevant underestimation of GFR by the creatinine-derived equations. The prevalence and prognostic significance of this particular proximal tubular damage in LCPT remain to be determined.

Mechanisms Underpinning Increased Plasma Creatinine Levels in Patients Receiving Vemurafenib for Advanced Melanoma

Context

Serum creatinine has been reported to increase in patients receiving Vemurafenib, yet neither the prevalence nor the mechanism of this adverse event are known.

Objective

We aimed to evaluate the frequency and the mechanisms of increases in plasma creatinine level in patients receiving Vemurafenib for advanced melanoma.

Methods

We performed a retrospective monocentric study including consecutive patients treated with Vemurafenib for an advanced melanoma. We collected clinical and biological data concerning renal function before introduction of Vemurafenib and in the course of monthly follow-up visits from March 2013 to December 2014. Cystatin C-derived glomerular filtration rate was evaluated before and after Vemurafenib initiation, as increase in serum cystatin C is specific to a decrease in the glomerular filtration rate. We also performed thorough renal explorations in 3 patients, with measurement of tubular secretion of creatinine before and after Vemurafenib initiation and a renal biopsy in 2 patients.

Results

70 patients were included: 97% of them displayed an immediate, and thereafter stable, increase in creatinine (+22.8%) after Vemurafenib initiation. In 44/52 patients in whom Vemurafenib was discontinued, creatinine levels returned to baseline. Serum cystatin C increased, although proportionally less than serum creatinine, showing that creatinine increase under vemurafenib was indeed partly due to a renal function impairment. In addition, renal explorations demonstrated that Vemurafenib induced an inhibition of creatinine tubular secretion.

Conclusion

Thus, Vemurafenib induces a dual mechanism of increase in plasma creatinine with both an inhibition of creatinine tubular secretion and slight renal function impairment. However, this side effect is mostly reversible when Vemurafenib is discontinued, and should not lead physicians to discontinue the treatment if it is effective.

Six Months of Hydroxyurea Reduces Albuminuria in Patients with Sickle Cell Disease

The earliest symptom of glomerular injury in patients with sickle cell disease (SCD) is microalbuminuria. The effect of hydroxyurea (HU) on urine albumin-to-creatinine ratio (ACR) is unclear and should be determined, because increasing numbers of patients with SCD take this drug to improve red blood cell function. In this cohort study of 58 SS-homozygous adults with SCD who initiated HU therapy, we evaluated ACR changes and relationships of these changes with demographic, clinical, and biologic parameters at HU initiation (baseline) and 6 months later (follow-up). Between baseline and follow-up, ACR declined significantly for the entire population (3.0-1.7 mg/mmol; P<0.01), but this was primarily driven by the ACR reduction in the microalbuminuria subgroup (8.1-2.3 mg/mmol; P=0.03; n=23). According to bivariate analyses on 39 patients who did not receive a blood transfusion during the study period, the baseline to follow-up ACR decline was strongly associated with decreases in levels of hemolysis markers, percentage of dense red blood cells, and systolic BP. Bivariate analysis also revealed a close association between the ACR decrease and high baseline levels of hemolysis markers and percentage of dense red blood cells. These results show that urine ACR decreased significantly after 6 months of HU and confirm a close relationship between ACR and hemolysis evolution in patients with SCD.

Membranous Nephropathy Associated With Immunological Disorder-Related Liver Disease: A Retrospective Study of 10 Cases

The association between membranous nephropathy (MN) and immunological disorder-related liver disease has not been extensively investigated, and the specific features of this uncommon association, if any, remain to be determined.We retrospectively identified 10 patients with this association. We aimed to describe the clinical, biological, and pathological characteristics of these patients and their therapeutic management. The possible involvement of the phospholipase A2 receptor (PLA2R) in these apparent secondary forms of MN was assessed by immunohistochemistry with renal and liver biopsy specimens.The mean delay between MN and liver disease diagnoses was 3.9 years and the interval between the diagnosis of the glomerular and liver diseases was <1.5 years in 5 patients. MN was associated with a broad spectrum of liver diseases including primary biliary cirrhosis (PBC), autoimmune hepatitis (AIH), and primary sclerosing cholangitis (PSC). AIH whether isolated (n = 3) or associated with PBC (n = 2) or PSC (n = 2) was the most frequent autoimmune liver disease. Circulating PLA2R antibodies were detected in 4 out of 9 patients but the test was performed under specific immunosuppressive treatment in 3 out of 9 patients. Seven of the 9 patients with available renal tissue specimens displayed enhanced expression of PLA2R in glomeruli whereas PLA2R was not expressed in liver parenchyma from these patients or in normal liver tissue. The study of immunoglobulin (Ig) subclasses of deposits in glomeruli revealed that the most frequent pattern was the coexistence of IgG1 and IgG4 immune deposits with IgG4 predominating.Detection of PLA2R antibodies in glomeruli but not in liver parenchyma is a common finding in patients with MN associated with autoimmune liver disease, suggesting that these autoantibodies are not exclusively detected in idiopathic MN.

Phospholipase A2 receptor and sarcoidosis-associated membranous nephropathy

Of the glomerulonephritis associated with sarcoidosis, membranous nephropathy (MN) is the most prevalent. Coincidence or a causal relationship between these two diseases is unclear. Here, we present for the first time a high prevalence of PLA2R-related MN among patients with MN associated with active sarcoidosis. Our results suggest some causal link between sarcoidosis and PLA2R-related MN. Detection of anti-PLA2R antibodies in serum or PLA2R antigen in biopsy should not be taken as evidence against a secondary cause, particularly sarcoidosis. This important observation can affect treatment decision in these patients.

Clinicopathological study of glomerular diseases associated with sarcoidosis: a multicenter study

Background

The association between sarcoidosis and glomerular diseases has not been extensively investigated in a large series and the potential features of this uncommon association remain to be determined.

Methods

We retrospectively identified 26 patients with biopsy-proven glomerular lesions that occurred in a sarcoidosis context. Potential remission of glomerular disease and sarcoidosis under specific treatment (steroid and/or immunosuppressive agents) was recorded for all patients. Demographic, clinical and biological characteristics were assessed at the time of kidney biopsy for each patient. Therapeutic data were analyzed for all patients.

Results

Glomerular disease occurred after the diagnosis of sarcoidosis in 11 of 26 cases (42%) (mean delay of 9.7 years). In six patients (23%), the glomerulopathy preceded the sarcoidosis diagnosis (mean delay 8 years). In the last nine patients (35%), both conditions occurred simultaneously. The most frequent glomerular disease occurring in sarcoidosis patients was membranous nephropathy in eleven cases. Other glomerular lesions included IgA nephropathy in six cases, focal segmental glomerulosclerosis in four patients, minimal change nephrotic syndrome for three patients and proliferative lupus nephritis in two patients. Granulomatous interstitial nephritis was associated with glomerular disease in six patients and was exclusively found in patients in whom the both disease occurred simultaneously. In nine patients with simultaneous glomerular and sarcoidosis diseases, we observed a strong dissociation between glomerular disease and sarcoidosis in terms of steroid responsiveness. At the end of the follow-up (mean of 8.4 years), six patients had reached end-stage renal disease and three patients had died.

Conclusions

A wide spectrum of glomerular lesions is associated with sarcoidosis. The close temporal relationship observed in some patients suggests common causative molecular mechanisms of glomerular injury but complete remission of both diseases in response to exclusive steroid therapy is infrequent.

[Kidney involvement in sarcoidosis]

Sarcoidosis is a chronic multisystemic inflammatory disorder of unknown etiology, characterized by the presence of non-necrotizing epithelioid and giant cell granulomas. Various renal manifestations have been reported in patients with sarcoidosis. Disorders of bone and mineral metabolism related to the overexpression of 25-hydroxyvitamin-D1α-hydroxylase by alveolar and granuloma macrophages are frequently associated with sarcoidosis. Hypercalcemia and hypercalciuria are a major cause of renal injury predisposing to pre renal azotemia, acute tubular necrosis, nephrolithiasis and nephrocalcinosis. Therapeutic management of hypercalcemia includes preventive measures (limited sunlight exposure, limited vitamin D and calcium intakes, and adequate hydration) and specific treatment in cases of severe hypercalcemia (corticosteroid therapy, chloroquine or ketoconazole). Granulomatous tubulointerstitial nephritis is the most common renal lesion associated with sarcoidosis leading to end stage renal disease in some patients. In these cases, interstitial fibrosis seems to appear early in the course of sarcoidosis and is a major prognostic factor requiring rapid corticosteroid therapy to reduce the risk of severe renal impairment. Membranous nephropathy seems to be the most frequent glomerular disease that may occur in association with sarcoidosis. Among kidney allograft recipients, the risk of recurrence of granulomatous tubulointerstitial nephritis is high and may have a negative impact on the graft survival.