Defining DIOS and constipation in cystic fibrosis with a multicentre study on the incidence, characteristics, and treatment of DIOS

Characterization of defects in ion transport and tissue development in cystic fibrosis transmembrane conductance regulator (CFTR)-knockout rats

Animal models for cystic fibrosis (CF) have contributed significantly to our understanding of disease pathogenesis. Here we describe development and characterization of the first cystic fibrosis rat, in which the cystic fibrosis transmembrane conductance regulator gene (CFTR) was knocked out using a pair of zinc finger endonucleases (ZFN). The disrupted Cftr gene carries a 16 base pair deletion in exon 3, resulting in loss of CFTR protein expression. Breeding of heterozygous (CFTR^+/−) rats resulted in Mendelian distribution of wild-type, heterozygous, and homozygous (CFTR^−/−) pups. Nasal potential difference and transepithelial short circuit current measurements established a robust CF bioelectric phenotype, similar in many respects to that seen in CF patients. Young CFTR^−/− rats exhibited histological abnormalities in the ileum and increased intracellular mucus in the proximal nasal septa. By six weeks of age, CFTR^−/− males lacked the vas deferens bilaterally. Airway surface liquid and periciliary liquid depth were reduced, and submucosal gland size was abnormal in CFTR^−/− animals. Use of ZFN based gene disruption successfully generated a CF animal model that recapitulates many aspects of human disease, and may be useful for modeling other CF genotypes, including CFTR processing defects, premature truncation alleles, and channel gating abnormalities.

Gastrointestinal surgery in cystic fibrosis: a 20-year review

OBJECTIVES

The purpose of this study was to evaluate outcomes of the surgical management for meconium ileus (MI) and Distal Intestinal Obstruction Syndrome (DIOS) in Cystic Fibrosis (CF).

METHODS

Children born between 1990 and 2010 were identified using a regional CF database. Retrospective case note analysis was performed. Outcome measures for MI were mortality, relaparotomy rate, length of stay (LOS), time on parental nutrition (TP), and time to full feeds (TFF). Outcome measures for DIOS were: age of onset, number of episodes, and need for laparotomy.

RESULTS

Seventy-five of 376 neonates presented with MI. Fifty-four (92%) required laparotomy. Contrast enema decompression was attempted in nineteen. There were no post-operative deaths. Thirty-nine (72%) neonates with MI were managed with stomas. LOS was longer in those managed with stomas (p=0.001) and in complex MI (p=0.002). Thirty-five patients were treated for DIOS. Twenty-five patients were managed with gastrograffin. Ten patients underwent surgical management of DIOS. Overall, MI did not predispose to later development of DIOS. There was a significantly greater incidence of laparotomy for DIOS in children who had MI.

CONCLUSION

The proportion of neonates with complex meconium ileus was high (49%) and may explain the infrequent utilisation of radiological decompression. Complex MI or management with stomas both significantly increase LOS. Re-laparotomy rate is high (22%) in MI irrespective of the type of management. DIOS is not a benign condition, particularly when the child has had previous abdominal surgery. Early referral to a surgical team is essential in these children.

Distal intestinal obstruction syndrome in cystic fibrosis: presentation, outcome and management in a tertiary hospital (2007-2012)

BACKGROUND

Cystic fibrosis (CF) can result in distal intestinal obstruction syndrome (DIOS) due to inspissated mucus. This paper describes the clinicopathological characteristics of adult CF patients with DIOS and assesses risk factors for surgery.

METHODS

A retrospective audit of CF patients at the Alfred Hospital from January 2007 to February 2012 was carried out. Patients who had 'bowel obstruction or constipation' were abstracted from the database, and medical records were reviewed for a diagnosis of DIOS.

RESULTS

Forty-five encounters of 35 patients were extracted. Twenty-five (83%) patients were homozygous for the delta F508 mutations, 29 (85%) had pancreatic insufficiency and 15 (44%) had a lung transplant. Patients presented with abdominal pain (96% of encounters), nausea (76% of encounters) and vomiting (67% of encounters). Computed tomography (CT) was performed in 20 episodes. Compared with CT, abdominal X-ray had a sensitivity of 63% (95% confidence interval (CI) 30-89%) and specificity of 33% (95% CI 8-70%) for detecting DIOS with obstruction. Forty-one (91%) encounters resolved with medical management within 2-3 days. Three patients required surgical intervention in four episodes. Previous laparotomy (odds ratio (OR) 28.5, 95% CI 1.3-624, P=0.03) and history of meconium ileus (OR 14, 95% CI 1-192, P<0.05) were statistically significant predictors of progression to surgical management.

CONCLUSION

In most patients with DIOS, the obstruction resolves with medical management. Early consultation with a CF service, assessment for a surgical abdomen and involvement of surgeons where appropriate is recommended. A history of previous laparotomy is a risk factor for the need for surgical intervention.

The cystic fibrosis intestine

The clinical manifestations of cystic fibrosis (CF) result from dysfunction of the cystic fibrosis transmembrane regulator protein (CFTR). The majority of people with CF have a limited life span as a consequence of CFTR dysfunction in the respiratory tract. However, CFTR dysfunction in the gastrointestinal (GI) tract occurs earlier in ontogeny and is present in all patients, regardless of genotype. The same pathophysiologic triad of obstruction, infection, and inflammation that causes disease in the airways also causes disease in the intestines. This article describes the effects of CFTR dysfunction on the intestinal tissues and the intraluminal environment. Mouse models of CF have greatly advanced our understanding of the GI manifestations of CF, which can be directly applied to understanding CF disease in humans.

Study design considerations for evaluating the efficacy and safety of pancreatic enzyme replacement therapy in patients with cystic fibrosis

In 2006, the US FDA issued a 'Guidance for Industry' regarding submission of New Drug Applications for pancreatic enzyme replacement therapy (PERT) products. Five oral delayed-release PERT products have been approved by the FDA, and several others are under development and/ or evaluation for New Drug Application submission. We present in this paper recommendations of the Cystic Fibrosis Foundation's Cystic Fibrosis (CF) Therapeutics Development Network and Data Safety Monitoring Board regarding study design considerations for evaluating PERT products in patients with CF. Careful attention to study design and accuracy of the outcome measures has confirmed our understanding of the efficacy and safety of PERT for the treatment of exocrine pancreatic insufficiency of CF.

Intestinal obstruction secondary to adhesions in an infant with cystic fibrosis

We report the case of a 9-week-old boy with cystic fibrosis (CF) who presented with intestinal obstruction. He was initially diagnosed with distal intestinal obstruction syndrome (DIOS) and started on laxatives and gastrograffin. This conservative management was unsuccessful and he therefore underwent an exploratory laparotomy. Despite not having undergone any previous surgery, extensive intra-abdominal adhesions were identified as the cause of the intestinal obstruction. The only previous abdominal pathology occurred in the neonatal period prior to his diagnosis of CF, when he was managed conservatively for possible necrotising enterocolitis. We hypothesise that this episode was associated with a subclinical bowel perforation that led to the formation of intra-abdominal adhesions. Although DIOS is the commonest cause of intestinal obstruction in children with CF, this case highlights that surgical causes should always be considered. It also demonstrates that the intra-abdominal adhesions can occur in the absence of previous surgery.

The gastrointestinal mucus system in health and disease

Mucins--large, highly glycosylated proteins--are important for the luminal protection of the gastrointestinal tract. Enterocytes have their apical surface covered by transmembrane mucins and goblet cells produce the secreted gel-forming mucins that form mucus. The small intestine has a single unattached mucus layer, which in cystic fibrosis becomes attached, accounting for the intestinal manifestations of this disease. The stomach and colon have two layers of mucus; the inner layer is attached and the outer layer is less dense and unattached. In the colon, the outer mucus layer is the habitat for commensal bacteria. The inner mucus layer is impervious to bacteria and is renewed every hour by surface goblet cells. The crypt goblet cells have the ability to restitute the mucus layer by secretion, for example after an ischaemic challenge. Proteases of certain parasites and some bacteria can cleave mucins and dissolve the mucus as part of their pathogenicity. The inner mucus layer can, however, also become penetrable to bacteria by several other mechanisms, including aberrations in the immune system. When bacteria reach the epithelial surface, the immune system is activated and inflammation is triggered. This mechanism might occur in some types of ulcerative colitis.

Intestinal CFTR expression alleviates meconium ileus in cystic fibrosis pigs

Cystic fibrosis (CF) pigs develop disease with features remarkably similar to those in people with CF, including exocrine pancreatic destruction, focal biliary cirrhosis, micro-gallbladder, vas deferens loss, airway disease, and meconium ileus. Whereas meconium ileus occurs in 15% of babies with CF, the penetrance is 100% in newborn CF pigs. We hypothesized that transgenic expression of porcine CF transmembrane conductance regulator (pCFTR) cDNA under control of the intestinal fatty acid-binding protein (iFABP) promoter would alleviate the meconium ileus. We produced 5 CFTR-/-;TgFABP>pCFTR lines. In 3 lines, intestinal expression of CFTR at least partially restored CFTR-mediated anion transport and improved the intestinal phenotype. In contrast, these pigs still had pancreatic destruction, liver disease, and reduced weight gain, and within weeks of birth, they developed sinus and lung disease, the severity of which varied over time. These data indicate that expressing CFTR in intestine without pancreatic or hepatic correction is sufficient to rescue meconium ileus. Comparing CFTR expression in different lines revealed that approximately 20% of wild-type CFTR mRNA largely prevented meconium ileus. This model may be of value for understanding CF pathophysiology and testing new preventions and therapies.

Gastrointestinal complications of cystic fibrosis

The cystic fibrosis transmembrane regulator protein (CFTR) is an ion channel in the apical surface of epithelial membranes that regulates other ion channels. Dysfunction of CFTR leads to the clinical entity of CF when mutations in CFTR are inherited in an autosomal recessive fashion. Although airway obstruction, inflammation, and infection are usually the most serious consequences of CFTR dysfunction because they lead to respiratory failure, CFTR dysfunction affects the intestinal tract and the pancreatic and hepatobiliary ducts in a similar fashion, leading to significant morbidity. This review outlines pathophysiology and common gastrointestinal ailments in the CF population along with current medical and surgical management.

Maintenance of nutritional status in patients with cystic fibrosis: new and emerging therapies

Poor clinical outcomes in cystic fibrosis are often associated with undernutrition. Normal growth and development should be achieved in cystic fibrosis, and nutritional counseling is paramount at all ages. Prevention and early detection of growth failure is the key to successful nutritional intervention. The advance in nutritional management is certainly one factor that has contributed to the improved survival in recent decades. This review outlines the major nutritional parameters in the management of the patient with cystic fibrosis, including recent advances in pancreatic enzyme replacement therapy and fat-soluble vitamin therapy. There are sections on complicated clinical situations which directly affect nutrition, for example, before and after lung transplantation, cystic fibrosis-related diabetes, and bone health.

Beyond appendicitis: evaluation and surgical treatment of pediatric acute abdominal pain

PURPOSE OF REVIEW

Evaluation of the child with acute abdominal pain is challenging because of the wide range of potential diagnoses. Presenting symptoms, clinical examination, and laboratory findings can guide selection of diagnostic imaging.

RECENT FINDINGS

Intussusception and intestinal malrotation are potentially serious causes of intestinal obstruction, which are best evaluated by ultrasound and upper gastrointestinal series, respectively. Ultrasound has diagnostic importance in the evaluation of multiple diseases, including appendicitis, by potentially decreasing the need for inpatient observation, cholecystitis and complications of gall stones such as pancreatitis, and ovarian diseases. Pelvic inflammatory disease should be considered in evaluation of a teenage girl with lower abdominal pain. Less common causes of acute abdominal pain include ingested foreign bodies, infected congenital anomalies, and perforated peptic ulcer disease.

SUMMARY

Presenting symptoms and physical examination findings can narrow the number of potential diagnoses in pediatric acute abdominal pain and thereby guide diagnostic imaging selection. Abdominal/pelvic ultrasound, rather than computed tomography scan, is the preferred modality for initial evaluation of many potential causes of pediatric abdominal pain.

Variation in MSRA modifies risk of neonatal intestinal obstruction in cystic fibrosis

Meconium ileus (MI), a life-threatening intestinal obstruction due to meconium with abnormal protein content, occurs in approximately 15 percent of neonates with cystic fibrosis (CF). Analysis of twins with CF demonstrates that MI is a highly heritable trait, indicating that genetic modifiers are largely responsible for this complication. Here, we performed regional family-based association analysis of a locus that had previously been linked to MI and found that SNP haplotypes 5' to and within the MSRA gene were associated with MI (P = 1.99 × 10(-5) to 1.08 × 10(-6); Bonferroni P = 0.057 to 3.1 × 10(-3)). The haplotype with the lowest P value showed association with MI in an independent sample of 1,335 unrelated CF patients (OR = 0.72, 95% CI [0.53-0.98], P = 0.04). Intestinal obstruction at the time of weaning was decreased in CF mice with Msra null alleles compared to those with wild-type Msra resulting in significant improvement in survival (P = 1.2 × 10(-4)). Similar levels of goblet cell hyperplasia were observed in the ilea of the Cftr(-/-) and Cftr(-/-)Msra(-/-) mice. Modulation of MSRA, an antioxidant shown to preserve the activity of enzymes, may influence proteolysis in the developing intestine of the CF fetus, thereby altering the incidence of obstruction in the newborn period. Identification of MSRA as a modifier of MI provides new insight into the biologic mechanism of neonatal intestinal obstruction caused by loss of CFTR function.

Cystic fibrosis lung transplantation

PURPOSE OF REVIEW

This review summarizes recently published investigations on issues pertaining to cystic fibrosis (CF) lung transplantation. We specifically focus on indications and candidate selection as well as infectious and noninfectious issues specific to CF lung transplant recipients.

RECENT FINDINGS

Recent studies have focused on candidate adequacy in high-risk CF patients. We review the current literature on individuals who develop respiratory failure requiring mechanical ventilation and those patients with a pretransplant diagnosis of pulmonary hypertension. Furthermore, the management of peri-operative infectious issues is reviewed including recurrent infections with multidrug-resistant bacterial, mycobacterial, and fungal organisms. Other CF-specific issues addressed include common comorbidities such as CF-related diabetes, gastroesophageal reflux, CF liver disease, and bone metabolism.

SUMMARY

Lung transplantation is a limited, but potentially life-saving therapeutic option for patients with CF. Optimal candidate selection and awareness of CF-specific issues in the pretransplant and posttransplant setting may lead to better long-term outcomes.

Intestinal obstruction syndromes in cystic fibrosis: meconium ileus, distal intestinal obstruction syndrome, and constipation

Meconium ileus at birth, distal intestinal obstruction syndrome (DIOS), and constipation are an interrelated group of intestinal obstruction syndromes with a variable severity of obstruction that occurs in cystic fibrosis patients. Long-term follow-up studies show that today meconium ileus is not a risk factor for impaired nutritional status, pulmonary function, or survival. DIOS and constipation are frequently seen in cystic fibrosis patients, especially later in life; genetic, dietary, and other associations have been explored. Diagnosis of DIOS is based on suggestive symptoms, with a right lower quadrant mass confirmed on abdominal radiography, whereas symptoms of constipation are milder and of longer standing. In DIOS, early aggressive laxative treatment with oral laxatives (polyethylene glycol) or intestinal lavage with balanced osmotic electrolyte solution and rehydration is required, which now makes the need for surgical interventions rare. Constipation can generally be well controlled with polyethylene glycol maintenance treatment.

Impaired mucosal barrier function in the small intestine of the cystic fibrosis mouse

OBJECTIVES

The intestinal mucosal barrier protects the body from the large numbers of microbes that inhabit the intestines and the molecules they release. Intestinal barrier function is impaired in humans with cystic fibrosis (CF), including reduced activity of the lipopolysaccharide-detoxifying enzyme intestinal alkaline phosphatase (IAP) and increased permeability. The objective of this study was to determine the suitability of using the CF mouse to investigate intestinal barrier function, and whether interventions that are beneficial for the CF mouse intestinal phenotype (antibiotics or laxative), would improve barrier function. Also tested were the effects of exogenous IAP administration.

MATERIALS AND METHODS

The Cftr(tm1UNC) mouse was used. IAP expression (encoded by the murine Akp3 gene) was measured by quantitative reverse transcription-polymerase chain reaction and enzyme activity. Intestinal permeability was assessed by measuring rhodamine-dextran plasma levels following gavage.

RESULTS

CF mice had 40% Akp3 mRNA expression and 30% IAP enzyme activity, as compared with wild-type mice. Oral antibiotics and laxative treatments normalized Akp3 expression and IAP enzyme activity in the CF intestine. CF mice had a 5-fold greater transfer of rhodamine-dextran from gut lumen to blood. Antibiotic and laxative treatments reduced intestinal permeability in CF mice. Administration of exogenous purified IAP to CF mice reduced intestinal permeability to wild-type levels and reduced small intestinal bacterial overgrowth by >80%.

CONCLUSIONS

The CF mouse intestine has impaired mucosal barrier function, similar to human CF. Interventions that improve other aspects of the CF intestinal phenotype (antibiotics and laxative) also increase IAP activity and decrease intestinal permeability in CF mice. Exogenous IAP improve permeability and strongly reduce bacterial overgrowth in CF mice, suggesting this may be a useful therapy for CF.

Guidelines for the diagnosis and management of distal intestinal obstruction syndrome in cystic fibrosis patients

Complete or incomplete intestinal obstruction by viscid faecal material in the terminal ileum and proximal colon - distal intestinal obstruction syndrome (DIOS) - is a common complication in cystic fibrosis. Estimates of prevalence range from 5 to 12 episodes per 1000 patients per year in children, with higher rates reported in adults. DIOS is mainly seen in patients with pancreatic insufficiency, positive history of meconium ileus and previous episodes of DIOS. DIOS is being described with increasing frequency following organ transplantation. Diagnosis is based on suggestive symptoms with a right lower quadrant mass confirmed on X-ray. The main differential is chronic constipation. Treatment consists of rehydration combined with stool softening laxatives or gut lavage with balanced electrolyte solutions. Rapid fluid shifts have been described following osmotic agents. Avoiding dehydration and optimizing pancreatic enzyme dosage may reduce the chance of further episodes. Prophylactic laxative therapy is widely used, but is not evidence-based.

A 2-year post-authorization safety study of high-strength pancreatic enzyme replacement therapy (pancreatin 40,000) in cystic fibrosis

OBJECTIVE

At the request of the Medicines and Healthcare Regulatory Agency and in agreement with the appropriate authorities, an observational, multi-center, non-interventional, post-authorization safety study of high-strength pancreatic enzymes was conducted.

RESEARCH DESIGN AND METHODS

Patients with exocrine pancreatic insufficiency due to cystic fibrosis (CF) who had previously taken high doses of pancreatic enzymes received pancreatin 40,000 capsules (Creon 40,000 Minimicrospheres, Abbott GmbH, Hanover, Germany) as part of their normal treatment for up to 2 years. Initial doses were calculated to match previous established doses in lipase units, with adjustment if required.

MAIN OUTCOME MEASURES

Safety focused on serious suspected adverse drug reactions. Maldigestion symptoms and body weight were also monitored. Patients were managed according to general guidelines common to all major CF units in the UK, although minor variations were expected. The coefficient of fat absorption was not assessed as this was a safety rather than an efficacy study.

RESULTS

Sixty-four patients were enrolled at nine UK centers. Two deaths occurred during the study, which were considered unrelated to therapy by investigators. There were no further serious suspected adverse drug reactions related to pancreatin 40,000 and no cases of fibrosing colonopathy. Daily lipase doses were reduced by 11% after switching to pancreatin 40,000. Maldigestion symptoms improved and mean body weight increased from baseline to last observation (mean + 6.1 kg in patients < 18 years old).

CONCLUSIONS

No safety concerns were identified with pancreatin 40,000 therapy for up to 2 years. Daily lipase doses were not increased when switching to pancreatin 40,000.

Efficacy and Safety of a New Formulation of Pancrelipase (Ultrase MT20) in the Treatment of Malabsorption in Exocrine Pancreatic Insufficiency in Cystic Fibrosis

Background. Pancreatic enzyme replacement therapy is the standard of care for treatment of malabsorption in patients with cystic fibrosis (CF) and exocrine pancreatic insufficiency (PI). Aim. To evaluate efficacy and safety of a new formulation of pancrelipase (Ultrase MT20) in patients with CF and PI. Coefficients of fat absorption (CFA%) and nitrogen absorption (CNA%) were the main efficacy parameters. Safety was evaluated by monitoring laboratory analyses, adverse events (AEs), and overall signs and symptoms. Methods. Patients (n = 31) were randomized in a crossover design comparing this pancrelipase with placebo during 2 inpatient evaluation periods (6-7 days each). Fat and protein/nitrogen ingestion and excretion were measured from food diaries and 72-hour stool collections. CFA% and CNA% were calculated for each period and compared. Results. Twenty-four patients provided analyzable data. This pancrelipase increased mean CFA% and CNA% (+34.7% and +25.7%, resp., P < .0001 for both), reduced stool frequency, and improved stool consistency compared with placebo. Placebo-treated patients reported more AEs, with gastrointestinal symptoms being the most frequently reported AE. Conclusions. This pancrelipase is a safe and effective treatment for malabsorption associated with exocrine PI in patients with CF.

Use of the chloride channel activator lubiprostone for constipation in adults with cystic fibrosis: a case series

OBJECTIVE

To describe the use of lubiprostone for constipation in 3 adults with cystic fibrosis (CF).

CASE SUMMARY

This case series describes the use of lubiprostone for the treatment of constipation in 3 adults with CF (mean +/- SD length of therapy 17.3 +/- 1.5 mo). All 3 patients were prescribed lubiprostone 24 microg twice daily after hospitalization for treatment of intestinal obstruction. Patient 1 continues on chronic polyethylene glycol (PEG) 3350 and lubiprostone and has not had a recurrence of obstruction. Patient 2 requires aggressive chronic therapy with PEG 3350, lubiprostone, and methylnaltrexone. She has had 1 recurrence of obstruction. Patient 3 continues with lubiprostone taken several times per week with good control of constipation and no recurrence of obstruction to date. The adverse effect profile has been tolerable in all 3 patients.

DISCUSSION

CF is caused by a genetic mutation resulting in a dysfunctional or absent CF transmembrane conductance regulator that normally functions as a chloride channel. This results in viscous secretions in multiple organ systems including the lungs and intestinal tract. Accumulation of viscous intestinal contents contributes to constipation, which is common among adults with CF and can sometimes lead to intestinal obstruction. Lubiprostone is indicated for chronic constipation and works by activating type 2 chloride channels (ClC-2) in the intestinal tract. Because it utilizes an alternate chloride channel, lubiprostone may be especially effective for constipation in patients with CF.

CONCLUSIONS

Lubiprostone provides an additional option for the treatment of constipation in adults with CF. Its use in the CF population deserves further study.