Constipation in pediatric cystic fibrosis patients: an underestimated medical condition

Presentation, characteristics and management of obstructive intestinal conditions in cystic fibrosis

Objective

Constipation and distal intestinal obstruction syndrome (DIOS) are common gastrointestinal manifestations of cystic fibrosis (CF). The primary aim was to describe the characteristics of constipation and DIOS hospitalisations in a paediatric and adult CF service over a 12-year period. The secondary aims were to determine the proportion of constipation and DIOS presentations which met the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) CF Working Group definitions and to describe management strategies of both conditions.

Method

A retrospective study of children and adults with CF who were admitted with a primary diagnosis of constipation or DIOS between 1 January 2011 and 31 December 2022. ESPGHAN definitions for constipation and DIOS were retrospectively applied to all admissions to determine if the primary medical diagnosis met ESPGHAN criteria.

Results

During the 12-year study period, 42 hospitalisations for constipation were recorded in 19 patients, and 33 hospitalisations for DIOS were recorded in 23 patients. 88.10% of constipation episodes met ESPGHAN definitions, compared with 3.0% of DIOS episodes. Constipation and DIOS were primarily treated with polyethylene glycol (PEG). The use of sodium amidotrizoate meglumine enemas was significantly higher in the DIOS group (p=0.045). Those admitted with DIOS were significantly less likely to be recommended a weaning dose of PEG (p=0.018).

Conclusion

Children and adults with CF are more commonly admitted for the management of constipation than DIOS. There is considerable variation in diagnostic and therapeutic practice, and this study highlights the need to enhance the translation and adoption of existing best-practice guidelines.

Cystic fibrosis and fat malabsorption: Pathophysiology of the cystic fibrosis gastrointestinal tract and the impact of highly effective CFTR modulator therapy

Cystic fibrosis (CF) is a progressive, genetic, multi-organ disease affecting the respiratory, digestive, endocrine, and reproductive systems. CF can affect any aspect of the gastrointestinal (GI) tract, including the esophagus, stomach, small intestine, colon, pancreas, liver, and gall bladder. GI pathophysiology associated with CF results from CF membrane conductance regulator (CFTR) dysfunction. The majority of people with CF (pwCF) experience exocrine pancreatic insufficiency resulting in malabsorption of nutrients and malnutrition. Additionally, other factors can cause or worsen fat malabsorption, including the potential for short gut syndrome with a history of meconium ileus, hepatobiliary diseases, and disrupted intraluminal factors, such as inadequate bile salts, abnormal pH, intestinal microbiome changes, and small intestinal bacterial overgrowth. Signs and symptoms associated with fat malabsorption, such as abdominal pain, bloating, malodorous flatus, gastroesophageal reflux, nausea, anorexia, steatorrhea, constipation, and distal intestinal obstruction syndrome, are seen in pwCF despite the use of pancreatic enzyme replacement therapy. Given the association of poor nutrition status with lung function decline and increased mortality, aggressive nutrition support is essential in CF care to optimize growth in children and to achieve and maintain a healthy body mass index in adults. The introduction of highly effective CFTR modulator therapy and other advances in CF care have profoundly changed the course of CF management. However, GI symptoms in some pwCF may persist. The use of current knowledge of the pathophysiology of the CF GI tract as well as appropriate, individualized management of GI symptoms continue to be integral components of care for pwCF.

Nutritional management of people living with cystic fibrosis throughout life and disease continuum: Changing times, new challenges

Cystic fibrosis (CF) is a genetic disease caused by mutations in the gene encoding for the ion channel cystic fibrosis transmembrane conductance regulator (CFTR). The management of CF disease has evolved in recent decades from treating downstream disease manifestations affecting the airways, the lungs and the gastrointestinal system to addressing the CFTR gene defect. The advent of CFTR modulators, which correct the functionality of the defective CFTR, contributes to reshaping the landscape of CF demographics, prognosis and therapies, including nutritional management. A spectrum of clinical manifestations is emerging within the same patient population where undernutrition and nutritional deficiencies coexist with excessive weight gain and metabolic derangements. Such contrasting presentations challenge current practices, require adjustments to traditional approaches, and involve more individualised interventions. This narrative review examines the current state of knowledge on the nutritional management of people living with cystic fibrosis from early life to adulthood in the era of CFTR modulation.

Respiratory Infection and Inflammation in Cystic Fibrosis: A Dynamic Interplay among the Host, Microbes, and Environment for the Ages

The interplay between airway inflammation and infection is now recognized as a major factor in the pathobiology in cystic fibrosis (CF). A proinflammatory environment is seen throughout the CF airway resulting in classic marked and enduring neutrophilic infiltrations, irreversibly damaging the lung. Although this is seen to occur early, independent of infection, respiratory microbes arising at different timepoints in life and the world environment perpetuate this hyperinflammatory state. Several selective pressures have allowed for the CF gene to persist until today despite an early mortality. Comprehensive care systems, which have been a cornerstone of therapy for the past few decades, are now revolutionized by CF transmembrane conductance regulator (CTFR) modulators. The effects of these small-molecule agents cannot be overstated and can be seen as early as in utero. For an understanding of the future, this review looks into CF studies spanning the historical and present period.

Lubiprostone is non-selective activator of cAMP-gated ion channels and Clc-2 has a minor role in its prosecretory effect in intestinal epithelial cells

Loss of prosecretory Cl- channel CFTR activity is considered as the key cause of gastrointestinal disorders in cystic fibrosis including constipation and meconium ileus. Clc-2 is proposed as an alternative Cl- channel in intestinal epithelia that can compensate for CFTR loss-of-function. Lubiprostone is an FDA-approved drug with Clc-2 activation as its presumed mechanism of action. However, relative contribution of Clc-2 in intestinal Cl- secretion and the mechanism of action of lubiprostone remain controversial due to lack of selective Clc-2 inhibitors. Using recently identified selective Clc-2 inhibitor AK-42, we characterized the roles of Clc-2 in Cl- secretion in human intestinal epithelial T84 cells. Clc-2 inhibitor AK-42 had minimal (15%) inhibitory effect on secretory short-circuit current (Isc) induced by cAMP agonists, where subsequently applied CFTR inhibitor (CFTRinh-172) caused 2-3 fold greater inhibition. Similarly, AK-42 inhibited lubiprostone-induced secretory Isc by 20%, whereas CFTRinh-172 caused 2-3 fold greater inhibition. In addition to increasing CFTR and Clc-2-mediated apical Cl- conductance, lubiprostone increased basolateral membrane K+ conductance, which was completely reversed by cAMP-activated K+ channel inhibitor BaCl2 All components of lubiprostone-induced secretion (Clc-2, CFTR and K+ channels) were inhibited by ~65% with the extracellular Ca2+-sensing receptor (CaSR) activator cinacalcet that stimulates cAMP hydrolysis. Lastly, EP4 prostaglandin receptor inhibitor GW627368 pretreatment inhibited lubiprostone-induced secretion by 40% without any effect on forskolin response. Our findings suggest that Clc-2 has minor role in cAMP-induced intestinal Cl- secretion; and lubiprostone is not a selective Clc-2 activator, but general activator of cAMP-gated ion channels in human intestinal epithelial cells. Significance Statement Cl- channel Clc-2 activation is the proposed mechanism of action of the FDA-approved constipation drug lubiprostone. Using first-in-class selective Clc-2 inhibitor AK-42, we showed that Clc-2 has minor contribution in intestinal Cl- secretion induced by lubiprostone and cAMP agonists. We also found that lubiprostone is a general activator of cAMP-gated ion channels in human intestinal epithelial cells (via EP4 receptors). Our findings clarify the roles of Clc-2 in intestinal Cl- secretion and elucidate the mechanism of action of approved-drug lubiprostone.

Understanding Cystic Fibrosis Comorbidities and Their Impact on Nutritional Management

Cystic fibrosis (CF) is a chronic, multisystem disease with multiple comorbidities that can significantly affect nutrition and quality of life. Maintaining nutritional adequacy can be challenging in people with cystic fibrosis and has been directly associated with suboptimal clinical outcomes. Comorbidities of CF can result in significantly decreased nutritional intake and intestinal absorption, as well as increased metabolic demands. It is crucial to utilize a multidisciplinary team with expertise in CF to optimize growth and nutrition, where patients with CF and their loved ones are placed in the center of the care model. Additionally, with the advent of highly effective modulators (HEMs), CF providers have begun to identify previously unrecognized nutritional issues, such as obesity. Here, we will review and summarize commonly encountered comorbidities and their nutritional impact on this unique population.

Interventions for preventing distal intestinal obstruction syndrome (DIOS) in cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is the most common, life-limiting, genetically inherited disease. It affects multiple organs, particularly the respiratory system. However, gastrointestinal problems such as constipation and distal intestinal obstruction syndrome (DIOS) are also important and well-recognised complications in CF. They share similar symptoms e.g. bloating, abdominal pain, but are distinct conditions. Constipation occurs when there is gradual faecal impaction of the colon, but DIOS occurs when there is an accumulation of faeces and sticky mucus, forming a mass in the distal part of the small intestine. The mass may partially block the intestine (incomplete DIOS) or completely block the intestine (complete DIOS). Symptoms of DIOS can affect quality of life and other aspects of CF health, such as airway clearance, exercise, sleep and nutritional status. Treatment of constipation and prevention of complete bowel obstruction are required for gastrointestinal management in CF. However, many different strategies are used in clinical practice and there is a lack of consensus. The importance of this topic was highlighted in a recent research priority setting exercise by the James Lind Alliance.

OBJECTIVES

To evaluate the effectiveness and safety of laxative agents of differing types for preventing DIOS (complete and incomplete) in children and adults with CF.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. Date of search: 09 September 2021. We also searched online trial registries. Date of last search: 12 October 2021.

SELECTION CRITERIA

Randomised and quasi-randomised controlled parallel trials comparing laxative therapy for preventing DIOS (including osmotic agents, stimulants, mucolytics and substances with more than one action) at any dose to placebo, no treatment or an alternative laxative therapy, in people of any age with pancreatic sufficient or insufficient CF and any stage of lung disease. Randomised cross-over trials were judged on an individual basis.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trials for inclusion, extracted outcome data and performed a risk of bias assessment for the included data. We judged the certainty of the evidence using GRADE criteria.

MAIN RESULTS

We included one cross-over trial (17 participants) with a duration of 12 months, in which participants were randomly allocated to either cisapride (a gastro-prokinetic agent) or placebo for six months each. The trial had an unclear risk of bias for most domains but had a high risk of reporting bias. Radiograph scores revealed no difference in occurrence of DIOS between cisapride and placebo (narrative report, no data provided). There were no adverse effects. Symptom scores were the only secondary outcome within the review that were reported. Total gastrointestinal symptom scores favoured cisapride with a statistically significant mean difference (MD) of -7.60 (95% confidence interval (CI) -14.73 to -0.47). There was no significant difference at six months between cisapride and placebo for abdominal distension, MD -0.90 (95% CI -2.39 to 0.59) or abdominal pain, MD -0.4 (95% CI -2.05 to 1.25). The global symptom scores (whether individuals felt better or worse) were reported in the paper to favour cisapride and be statistically significant (P < 0.05). We assessed the available data to be very low certainty. There was a great deal of missing data from the included trial and the investigators failed to report numerical data for many outcomes. The overall risk of bias of the trial was unclear and it had a high risk for reporting bias. There was also indirectness; the trial drug (cisapride) has since been removed from the market in several countries due to adverse effects, thus it has no current applicability for preventing DIOS. The included trial also had very few participants, which downgraded the certainty a further level for precision.

AUTHORS' CONCLUSIONS

There is an absence of evidence for interventions for the prevention of DIOS. As there was only one included trial, we could not perform a meta-analysis of the data. Furthermore, the included trial compared a prokinetic agent (cisapride) that is no longer licensed for use in a number of countries due to the risk of serious cardiac events, a finding that came to light after the trial was conducted. Therefore, the limited findings from the trial are not applicable in current clinical practice. Overall, a great deal more research needs to be undertaken on gastrointestinal complications in CF, as this is a very poorly studied area compared to respiratory complications in CF.

Colonic Transit Time and Fecal Impaction in Children and Adolescents With Cystic Fibrosis-associated Constipation

BACKGROUND

Constipation is prevalent in pediatric cystic fibrosis (CF) patients and colonic motility has not been studied in this population. In this study, we aimed to evaluate the total and segmental colonic transit time in children and adolescents with CF based on the presence of constipation and radiological fecal impaction.

METHODS

In this case series, all patients aged 3 to 20 years of a CF reference center were invited to participate. CF-associated constipation was diagnosed based on the European Society for Paediatric Gastroenterology Hepatology and Nutrition criteria. Total and segmental colonic transit time was determined using radiopaque markers. Fecal impaction on plain abdominal radiography was assessed based on the Barr score.

RESULTS

Of the 43 eligible patients, 34 (79%) agreed to participate. Constipation was found in 44.1% of children and adolescents, predominantly in girls. The total colonic transit time (medians of 42 and 24 hours, respectively, P = 0.028) and the segmental right colon transit time (medians of 8 and 2 hours, respectively, P = 0.012) were significantly longer in CF-associated constipation group than in the group of patients without constipation. The frequency of radiological fecal impaction was similar in patients with (50.0%) and without (64.2%) CF-associated constipation (P = 0.70). There was no relationship between radiological fecal impaction and the total and segmental colonic transit time.

CONCLUSIONS

Children and adolescents with CF-associated constipation had a longer total and segmental right colon transit time. Colonic transit time was similar in patients with and without radiological fecal impaction.

Academy of Nutrition and Dietetics: 2020 Cystic Fibrosis Evidence Analysis Center Evidence-Based Nutrition Practice Guideline

The Academy of Nutrition and Dietetics Evidence Analysis Center conducted a systematic review of the literature to develop an evidence-based practice guideline for primary nutrition issues in cystic fibrosis (CF). This guideline is designed to complement and build upon existing evidence-based CF nutrition guidelines. The objective of this guideline was to provide recommendations for registered dietitian nutritionists in the United States delivering medical nutrition therapy to individuals with CF and their families that fill gaps in current evidence-based guidelines on topics that are crucial in order to improve health and prevent disease progression. This guideline provides 28 nutrition recommendations to guide medical nutrition therapy, including nutrition screening, nutrition assessment, and dietary intake. For topics outside the scope of this guideline, practitioners are referred to external, evidence-based recommendations. The CF landscape is evolving rapidly with breakthroughs in cystic fibrosis transmembrane regulator modulators changing CF at a cellular level. Medical nutrition therapy for individuals with CF from infancy through advanced age requires novel and individualized approaches. The Academy Evidence Analysis Library CF guidelines provide a framework for expanding upon current knowledge to determine effective nutrition strategies for individuals with CF through long and healthy futures.

Postprandial changes in gastrointestinal function and transit in cystic fibrosis assessed by Magnetic Resonance Imaging

BACKGROUND

Cystic fibrosis (CF) is a multi-system genetic disorder affecting >72,000 people worldwide. Most CF patients experience gastrointestinal symptoms and can develop complications. However, the mechanisms of CF gut disease are not well understood. We evaluated gut function and transit in CF using magnetic resonance imaging (MRI). We hypothesised oro-caecal transit time (OCTT) is longer in CF; with lower small bowel water content (SBWC).

METHODS

Twelve CF patients aged 12-40 years and 12 age and sex-matched controls underwent serial MRIs over 1 day with standardised meals. The primary endpoint was OCTT, assessed by the appearance of a food bolus in the caecum. Other measures included corrected SBWC and corrected colonic volume (both area under the curve, AUC), gastric half-emptying time and gastrointestinal symptoms.

RESULTS

OCTT was longer in CF (CF 330 mins [270, >360] vs. controls 210 mins [173, 315], p = 0.04), with no difference in gastric half-emptying times. Corrected SBWC was higher in CF (CF 62 L.min/m2 [36, 80] vs. controls 34 L.min/m2 [28, 41], p = 0.021); minimal postprandial decrease between T240 and T300 (CF 13 mL/m2 [-13, 57] vs. controls 102 mL/m2 [67, 108], p = 0.002) suggests impaired ileal emptying. Corrected colonic volumes were higher in CF (CF 186 L.min/m2 [167, 206] vs. controls 123 L.min/m2 [89, 146], p = 0.012). There were no differences in gastrointestinal symptoms.

CONCLUSIONS

MRI provides novel insights into CF pathophysiology. Sub-clinical ileal obstruction may be more prevalent than previously thought. Gastrointestinal MRI shows promise as an investigational tool in CF.

SLC26A6-selective inhibitor identified in a small-molecule screen blocks fluid absorption in small intestine

SLC26A6 (also known as putative anion transporter 1 [PAT1]) is a Cl-/HCO3- exchanger expressed at the luminal membrane of enterocytes where it facilitates intestinal Cl- and fluid absorption. Here, high-throughput screening of 50,000 synthetic small molecules in cells expressing PAT1 and a halide-sensing fluorescent protein identified several classes of inhibitors. The most potent compound, the pyrazolo-pyrido-pyrimidinone PAT1inh-B01, fully inhibited PAT1-mediated anion exchange (IC50 ~350 nM), without inhibition of the related intestinal transporter SLC26A3 (also known as DRA). In closed midjejunal loops in mice, PAT1inh-B01 inhibited fluid absorption by 50%, which increased to >90% when coadministered with DRA inhibitor DRAinh-A270. In ileal loops, PAT1inh-B01 blocked fluid absorption by >80%, whereas DRAinh-A270 was without effect. In colonic loops, PAT1inh-B01 was without effect, whereas DRAinh-A270 completely blocked fluid absorption. In a loperamide constipation model, coadministration of PAT1inh-B01 with DRAinh-A270 increased stool output compared with DRAinh-A270 alone. These results provide functional evidence for complementary and region-specific roles of PAT1 and DRA in intestinal fluid absorption, with PAT1 as the predominant anion exchanger in mouse ileum. We believe that PAT1inh-B01 is a novel tool to study intestinal ion and fluid transport and perhaps a drug candidate for small intestinal hyposecretory disorders such as cystic fibrosis-related meconium ileus and distal intestinal obstruction syndrome.

Luminal Gastrointestinal Manifestations of Cystic Fibrosis

PURPOSE OF REVIEW

People with cystic fibrosis (CF) are living longer. General age-related and CF-specific gastrointestinal symptoms are increasingly recognized. In this article, we review the latest data on luminal gastrointestinal manifestations in CF.

RECENT FINDINGS

People with CF have increased incidence of gastroesophageal reflux disease symptoms and often prescribed proton-pump inhibitors (PPI). PPI use may increase risk of pulmonary exacerbations. Evidence to support gastric fundoplication to improve pulmonary outcomes is limited. Features of intestinal dysmotility are common. There are distinct differences in the gut microbiome in the CF population which may have clinical implications. CF is a possible hereditary digestive cancer syndrome, particularly in regard to colorectal cancer (CRC) with earlier incidence of CRC and advanced colonic neoplasia. Early screening colonoscopy is warranted in the CF population. Gastrointestinal manifestations in CF are prevalent across all digestive organs. More study on the effect of interventions for symptomatic treatment and cancer screening is needed.

Designing the GALAXY study: Partnering with the cystic fibrosis community to optimize assessment of gastrointestinal symptoms

BACKGROUND

Gastrointestinal (GI) involvement among persons with cystic fibrosis (CF) is highly prevalent, representing a significant source of morbidity. Persons with CF have identified GI concerns as a top research priority, yet universal clinical outcome measures capturing many of the GI symptoms experienced in CF are lacking. The GALAXY study was envisioned to address this unmet need.

METHODS

The GALAXY study team partnered with Community Voice, a community of patients with CF and their caregivers, to identify the patient reported outcome measures that most accurately reflected their experience with GI symptoms in CF. We also surveyed CF care teams to identify the comfort level of various team members (providers, nurses and dieticians) in managing a variety of GI conditions.

RESULTS

Members of Community Voice identified the combination of PAC-SYM, PAGI-SYM, PAC-QOL and the Bristol Stool scale with three additional symptom-specific questions as patient-reported outcome measures that comprehensively captured the CF experience with GI disease. CF care team providers reported a high level of comfort in treating GI conditions including constipation (92%), GERD (93%), and gassiness (77%), however comfort level was limited to only first-line interventions.

CONCLUSION

By partnering with persons with CF as well as their caregivers and medical providers, the GALAXY study is designed to uniquely capture the prevalence and severity of GI involvement among persons with CF in a manner that reflects the CF patient experience. The results of GALAXY will inform the development of future interventional trials and serve as a reproducible and objective study endpoint.

Prevalence of constipation in cystic fibrosis patients: a systematic review of observational studies

OBJECTIVE

To systematically revise the literature in search of data about the prevalence of constipation in patients with cystic fibrosis according to the publications in this field, which partly refer to guidelines defined in 2010 by the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition.

SOURCES

Systematic review selecting articles based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, including Cystic Fibrosis patients of all ages. Sources of information were selected to identify the articles without period limitation: CADTH - Canadian Agency for Drugs and Technologies in Health, CINAHL Complete, Clinical Trials US NIH, Cochrane Library, Embase, MEDLINE via Ovid, Scopus, Web Of Science, PubMed, SciELO, MEDLINE and LILACS , Health Systems Evidence, PDQ Evidence, CRD Canadian Agency for Drugs and Technologies in Health, INAHTA - International Network of Agencies for Health Technology Assessment, and PEDro.

FINDINGS

The prevalence of constipation was reported in eight observational studies. Only two studies assessed the frequency of constipation as a primary objective; in the others, constipation was quoted along with the prevalence of the spectrum of gastrointestinal manifestations. Altogether, the publications included 2,018 patients, the reported prevalence varied from 10% to 57%. Only two of the six articles published after 2010 followed the definition recommended by the European Society.

CONCLUSIONS

Constipation is a frequent but still insufficiently assessed complaint of Cystic Fibrosis patients. The use of diverse diagnostic criteria restricts comparison and epidemiological conclusions, future studies should compulsorily apply the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition definition.

OMT for the Prevention and Management of Chronic Constipation and Distal Intestinal Obstructive Syndrome in Cystic Fibrosis: A Pilot Study

Context

Cystic fibrosis (CF) is an autosomal recessive genetic disorder primarily affecting the lungs and digestive system. Patients with CF often have multiorgan dysfunction, including chronic lung infections, pancreatic insufficiency, chronic constipation, and distal intestinal obstructive syndrome (DIOS).

Objective

To understand the impact of osteopathic manipulative treatment (OMT) on the prevention and management of gastrointestinal symptoms in patients with CF.

Methods

This study used OMT for physical manipulation of the viscera, spine, and other somatic components to improve bowel symptoms and prevent DIOS. These effects were achieved by releasing myofascial restrictions found in the abdomen and somatic structures with the intent to optimize the autonomic and lymphatic systems and improve range of motion.

Results

Four of 5 participants had a decrease in pain, and 3 participants had a reduced need for laxatives during treatment. Four participants had an overall increase in satisfaction with their bowel movements while being treated with OMT.

Conclusion

These findings support the use of OMT as a method for the management of chronic constipation and DIOS in the CF population. However, because of the small population size, more research with larger populations is needed.

Defective FXR-FGF15 signaling and bile acid homeostasis in cystic fibrosis mice can be restored by the laxative polyethylene glycol

The gastrointestinal phenotype of cystic fibrosis (CF) features intestinal bile acid (BA) malabsorption, impaired intestinal farnesoid X receptor (FXR) activation, and consequently reduced fibroblast growth factor 19 (FGF19, FGF15 in mice) production. The osmotic laxative polyethylene glycol (PEG) has been shown to decrease intestinal mucus accumulation in CF mice and could, by doing so, improve BA reabsorption. Here we determined the effect of PEG on BA excretion and FXR-FGF15 signaling in CF mice. Male Cftr^-/-tm1Unc (CF) and wild-type (WT) littermates were administered PEG 4000 in drinking water and fed either chow or a semisynthetic diet. PEG was withdrawn for 3 days before termination. Fecal BA excretion was measured at PEG dosages of 37 g/l (100%) and 0 g/l (0%). Ileal FXR activation was assessed by gene expression of its downstream targets Fgf15 and small heterodimer partner ( Shp). In CF mice, PEG withdrawal increased fecal BA excretion on either diet compared with full PEG dosage (chow, 2-fold, P = 0.06; semisynthetic, 4.4-fold, P = 0.007). PEG withdrawal did not affect fecal BA excretion in WT mice on either diet. After PEG withdrawal, gene expression levels of intestinal FXR target genes Fgf15 and Shp were decreased in CF mice but unaffected in WT littermates. PEG did not affect the gene expression of the main intestinal BA transporter apical sodium-dependent bile acid transporter (ASBT). PEG treatment ameliorates intestinal BA malabsorption in CF mice and restores intestinal FXR-FGF15 signaling, independent from Asbt gene expression. These findings highlight the potential of PEG in the prevention and treatment of the gastrointestinal phenotype of CF. NEW & NOTEWORTHY A gastrointestinal feature of cystic fibrosis is bile acid malabsorption and consequent impairment of farnesoid X receptor (FXR)-fibroblast growth factor 15 (FGF15) signaling. FXR-FGF15 signaling regulates various metabolic processes and could be implicated in metabolic and gastrointestinal complications of cystic fibrosis, such as diabetes and liver disease. In cystic fibrosis mice, treatment with the osmotic laxative polyethylene glycol is associated with decreased fecal bile acid loss and restoration of FXR-FGF15 signaling.

Linaclotide improves gastrointestinal transit in cystic fibrosis mice by inhibiting sodium/hydrogen exchanger 3

Gastrointestinal dysfunction in cystic fibrosis (CF) is a prominent source of pain among patients with CF. Linaclotide, a guanylate cyclase C (GCC) receptor agonist, is a US Food and Drug Administration-approved drug prescribed for chronic constipation but has not been widely used in CF, as the cystic fibrosis transmembrane conductance regulator (CFTR) is the main mechanism of action. However, anecdotal clinical evidence suggests that linaclotide may be effective for treating some gastrointestinal symptoms in CF. The goal of this study was to determine the effectiveness and mechanism of linaclotide in treating CF gastrointestinal disorders using CF mouse models. Intestinal transit, chloride secretion, and intestinal lumen fluidity were assessed in wild-type and CF mouse models in response to linaclotide. CFTR and sodium/hydrogen exchanger 3 (NHE3) response to linaclotide was also evaluated. Linaclotide treatment improved intestinal transit in mice carrying either F508del or null Cftr mutations but did not induce detectable Cl^- secretion. Linaclotide increased fluid retention and fluidity of CF intestinal contents, suggesting inhibition of fluid absorption. Targeted inhibition of sodium absorption by the NHE3 inhibitor tenapanor produced improvements in gastrointestinal transit similar to those produced by linaclotide treatment, suggesting that inhibition of fluid absorption by linaclotide contributes to improved gastrointestinal transit in CF. Our results demonstrate that linaclotide improves gastrointestinal transit in CF mouse models by increasing luminal fluidity through inhibiting NHE3-mediated sodium absorption. Further studies are necessary to assess whether linaclotide could improve CF intestinal pathologies in patients. GCC signaling and NHE3 inhibition may be therapeutic targets for CF intestinal manifestations. NEW & NOTEWORTHY Linaclotide's primary mechanism of action in alleviating chronic constipation is through cystic fibrosis transmembrane conductance regulator (CFTR), negating its use in patients with cystic fibrosis (CF). For the first time, our findings suggest that in the absence of CFTR, linaclotide can improve fluidity of the intestinal lumen through the inhibition of sodium/hydrogen exchanger 3. These findings suggest that linaclotide could improve CF intestinal pathologies in patients.

Bile acid homeostasis in gastrointestinal and metabolic complications of cystic fibrosis

With the improved treatment of the pulmonary complications of cystic fibrosis (CF), gastrointestinal problems have become more important in the morbidity in CF. A hallmark of the gastrointestinal phenotype of CF, apart from pancreatic insufficiency, is a disruption of bile acid homeostasis. Bile acid homeostasis is important for many gastrointestinal processes including fat absorption, inflammation, microbial composition, as well as regulation of whole body energy metabolism. This review describes the impairment of bile acid homeostasis in CF, its possible consequences for gastrointestinal and metabolic complications and its potential as a target for therapy.

Interventions for preventing distal intestinal obstruction syndrome (DIOS) in cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is the most common, life-limiting, genetically inherited disease. It affects multiple organs, particularly the respiratory system. However, gastrointestinal problems such as constipation and distal intestinal obstruction syndrome (DIOS) are also important and well-recognised complications in CF. They share similar symptoms e.g. bloating, abdominal pain, but are distinct conditions. Constipation occurs when there is gradual faecal impaction of the colon, but DIOS occurs when there is an accumulation of faeces and sticky mucus, forming a mass in the distal part of the small intestine. The mass may partially block the intestine (incomplete DIOS) or completely block the intestine (complete DIOS). Symptoms of DIOS can affect quality of life and other aspects of CF health, such as airway clearance, exercise, sleep and nutritional status. Treatment of constipation and prevention of complete bowel obstruction are required for gastrointestinal management in CF. However, many different strategies are used in clinical practice and there is a lack of consensus. The importance of this topic was highlighted in a recent research priority setting exercise by the James Lind Alliance.

OBJECTIVES

To evaluate the effectiveness and safety of laxative agents of differing types for preventing DIOS (complete and incomplete) in children and adults with CF.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. Date of search: 22 May 2018.We also searched online trial registries. Date of last search: 10 June 2018.

SELECTION CRITERIA

Randomised and quasi-randomised controlled parallel trials comparing laxative therapy for preventing DIOS (including osmotic agents, stimulants, mucolytics and substances with more than one action) at any dose to placebo, no treatment or an alternative laxative therapy, in people of any age with pancreatic sufficient or insufficient CF and any stage of lung disease. Randomised cross-over trials were judged on an individual basis.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trials for inclusion, extracted outcome data and performed a risk of bias assessment for the included data. We judged the quality of the evidence using GRADE criteria.

MAIN RESULTS

We included one cross-over trial (17 participants) with a duration of 12 months, in which participants were randomly allocated to either cisapride (a gastro-prokinetic agent) or placebo for six months each. The trial had an unclear risk of bias for most domains but had a high risk of reporting bias.Radiograph scores revealed no difference in occurrence of DIOS between cisapride and placebo (narrative report, no data provided). There were no adverse effects. Symptom scores were the only secondary outcome within the review that were reported. Total gastrointestinal symptom scores favoured cisapride with a statistically significant mean difference (MD) of -7.60 (95% confidence interval (CI) -14.73 to -0.47). There was no significant difference at six months between cisapride and placebo for abdominal distension, MD -0.90 (95% CI -2.39 to 0.59) or abdominal pain, MD -0.4 (95% CI -2.05 to 1.25). The global symptom scores (whether individuals felt better or worse) were reported in the paper to favour cisapride and be statistically significant (P < 0.05).We assessed the available data to be very low quality. There was a great deal of missing data from the included trial and the investigators failed to report numerical data for many outcomes. The overall risk of bias of the trial was unclear and it had a high risk for reporting bias. There was also indirectness; the trial drug (cisapride) has since been removed from the market in several countries due to adverse effects, thus it has no current applicability for preventing DIOS. The included trial also had very few participants, which downgraded the quality a further level for precision.

AUTHORS' CONCLUSIONS

There is an absence of evidence for interventions for the prevention of DIOS. As there was only one included trial, we could not perform a meta-analysis of the data. Furthermore, the included trial compared a prokinetic agent (cisapride) that is no longer licensed for use in a number of countries due to the risk of serious cardiac events, a finding that came to light after the trial was conducted. Therefore, the limited findings from the trial are not applicable in current clinical practice.Overall, a great deal more research needs to be undertaken on gastrointestinal complications in CF, as this is a very poorly studied area compared to respiratory complications in CF.

Practical approach to the gastrointestinal manifestations of cystic fibrosis

Cystic fibrosis (CF) is the most common, life-shortening, genetic illness affecting children in Australia and New Zealand. The genetic abnormality results in abnormal anion transport across the apical membrane of epithelial cells in a number of organs, including the lungs, gastrointestinal tract, liver and genito-urinary tract. Thus, CF is a multi-system disorder that requires a multi-disciplinary approach. Respiratory disease is the predominant cause of both morbidity and mortality in patients with CF. However, there are significant and clinically relevant gastrointestinal, liver, pancreatic and nutritional manifestations that must be detected and managed in a timely and structured manner. The aim of this review is to provide evidence-based information and clinical algorithms to guide the nutritional and gastrointestinal management of patients with CF.

Roles of NHERF Family of PDZ-Binding Proteins in Regulating GPCR Functions

Multicellular organisms are equipped with an array of G-protein-coupled receptors (GPCRs) that mediate cell-cell signaling allowing them to adapt to environmental cues and ultimately survive. This is mechanistically possible through complex intracellular GPCR machinery that encompasses a vast network of proteins. Within this network, there is a group called scaffolding proteins that facilitate proper localization of signaling proteins for a quick and robust GPCR response. One protein family within this scaffolding group is the PSD-95/Dlg/ZO-1 (PDZ) family which is important for GPCR localization, internalization, recycling, and downstream signaling. Although the PDZ family of proteins regulate the functions of several receptors, this chapter focuses on a subfamily within the PDZ protein family called the Na⁺/H⁺ exchanger regulatory factors (NHERFs). Here we extensively review the predominantly characterized roles of NHERFs in renal phosphate absorption, intestinal ion regulation, cancer progression, and immune cell functions. Finally, we discuss the future perspectives and possible clinical application of targeting NHERFs in several disorders.

Prevalence and impact of pelvic floor dysfunction in an adult cystic fibrosis population: a questionnaire survey

INTRODUCTION AND HYPOTHESIS

Pelvic floor (PF) dysfunction in patients with cystic fibrosis (CF) is poorly understood due to lack of research. The aim of this study was to examine the prevalence, risk factors and bothersomeness of PF dysfunction and its implications for the clinical management of CF.

METHODS

Of 64 adults with CF approached at a tertiary hospital, 60 were surveyed. A clinically meaningful score on the Australian Pelvic Floor Questionnaire (APFQ) is ≥1 in each of the bladder, bowel, sexual function and prolapse sections or a global PF score of ≥3. A frequency Likert scale was used to analyse the impact of PF dysfunction on the ability to perform physiotherapy lung management when well and unwell.

RESULTS

The prevalence of clinically meaningful bladder dysfunction was 39 % in women and 12 % in men, the prevalence of bowel dysfunction was 54 % in women and 44 % in men, and the prevalence of sexual dysfunction was 43 % in women and 65 % in men. APFQ scores were clinically meaningful only for bowel dysfunction in women (median 1.47, IQR 0.59 - 2.28). PF dysfunction constrains lung management in up to 22 % of patients when well and in 37 % of patients when unwell.

CONCLUSIONS

PF dysfunction affects the adult CF population, with PF symptoms limiting the ability of up to one in three patients to participate in physiotherapy management.

Role of CFTR in epithelial physiology

Salt and fluid absorption and secretion are two processes that are fundamental to epithelial function and whole body fluid homeostasis, and as such are tightly regulated in epithelial tissues. The CFTR anion channel plays a major role in regulating both secretion and absorption in a diverse range of epithelial tissues, including the airways, the GI and reproductive tracts, sweat and salivary glands. It is not surprising then that defects in CFTR function are linked to disease, including life-threatening secretory diarrhoeas, such as cholera, as well as the inherited disease, cystic fibrosis (CF), one of the most common life-limiting genetic diseases in Caucasian populations. More recently, CFTR dysfunction has also been implicated in the pathogenesis of acute pancreatitis, chronic obstructive pulmonary disease (COPD), and the hyper-responsiveness in asthma, underscoring its fundamental role in whole body health and disease. CFTR regulates many mechanisms in epithelial physiology, such as maintaining epithelial surface hydration and regulating luminal pH. Indeed, recent studies have identified luminal pH as an important arbiter of epithelial barrier function and innate defence, particularly in the airways and GI tract. In this chapter, we will illustrate the different operational roles of CFTR in epithelial function by describing its characteristics in three different tissues: the airways, the pancreas, and the sweat gland.

Gastrointestinal, Pancreatic, and Hepatobiliary Manifestations of Cystic Fibrosis

Pulmonary disease is the primary cause of morbidity and mortality in people with cystic fibrosis (CF), but significant involvement within gastrointestinal, pancreatic, and hepatobiliary systems occurs as well. As in the airways, defects in CFTR alter epithelial surface fluid, mucus viscosity, and pH, increasing risk of stasis through the various hollow epithelial-lined structures of the gastrointestinal tract. This exerts secondary influences that are responsible for most gastrointestinal, pancreatic, and hepatobiliary manifestations of CF. Understanding these gastrointestinal morbidities of CF is essential in understanding and treating CF as a multisystem disease process and improving overall patient care.

Beyond pancreatic insufficiency and liver disease in cystic fibrosis

Cystic fibrosis is a life shortening hereditary disease, primarily leading to progressive pulmonary infection and exocrine pancreatic dysfunction. Several gastrointestinal complications other than malabsorption can arise during the disease course and with the progressively increasing life span of patients with CF; new and more rare complications are being recognized. We review the literature on gastrointestinal manifestations in CF, excluding the liver and pancreas.

CONCLUSION

We describe the clinical presentation and treatment of more common conditions like gastroesophageal reflux, small intestinal bacterial overgrowth, intussusception, meconium ileus, distal intestinal obstruction syndrome, and constipation, and we also discuss what is known on celiac disease, appendicitis, fibrosing colonopathy, inflammation and inflammatory bowel disease and gastrointestinal cancer.

WHAT IS KNOWN

• Gastrointestinal complications arise early in the course of the disease and have a severe impact on the quality of life of the patients. What is New: • This review is a concise summary of the current literature on gastrointestinal complications of cystic fibrosis. • We focused on clinical presentation and diagnostic investigations and provide a comprehensive resume of the current treatment options.

High ambient temperature and risk of intestinal obstruction in cystic fibrosis

AIMS

Distal intestinal obstruction syndrome (DIOS) and constipation in cystic fibrosis (CF) are conditions associated with impaction and/or obstruction by abnormally viscid mucofaecal material within the intestinal lumen. Dehydration has been proposed as a risk factor for DIOS and constipation in CF. The study primarily aimed to determine whether warmer ambient temperature and lower rainfall are risk factors for DIOS and constipation in CF.

METHODS

Hospitalisations for DIOS (incomplete or complete) and/or constipation were retrospectively identified (2000-2012). Genotype, phenotype, temperatures and rainfall data (for the week preceding and season of hospitalisation) were collected.

RESULTS

Twenty-seven DIOS (59.3% incomplete; 40.7% complete) and 44 constipation admissions were identified. All admitted patients were pancreatic insufficient. Meconium ileus was significantly more likely in DIOS than constipation (64.7% vs. 33.3%; P = 0.038) and in complete than incomplete DIOS (100% vs. 57.1%; P = 0.04). The maximum temperature of the week before DIOS admission (mean (standard deviation) = 28.0 (5.8) °C) was significantly higher than the maximum temperature of the season of admission (25.2 (3.4) °C; P = 0.002). Similarly, the maximum temperature of the week before hospitalisation for constipation (mean (standard deviation) = 27.9 (6.3) °C) was significantly warmer compared with the season of admission (24.0 (4.1) °C; P < 0.0001). There were no significant differences between levels of rainfall during the week before hospitalisation and the season of admission for both DIOS and constipation.

CONCLUSIONS

Relatively high ambient temperature may play a role in the pathogenesis of DIOS and constipation in CF.

Nutritional Status Improved in Cystic Fibrosis Patients with the G551D Mutation After Treatment with Ivacaftor

BACKGROUND

The cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gating mutation G551D prevents sufficient ion transport due to reduced channel-open probability. Ivacaftor, an oral CFTR potentiator, increases the channel-open probability.

AIM

To further analyze improvements in weight and body mass index (BMI) in two studies of ivacaftor in patients aged ≥6 years with CF and the G551D mutation.

METHODS

Patients were randomized 1:1 to ivacaftor 150 mg or placebo every 12 h for 48 weeks. Primary end point (lung function) was reported previously. Other outcomes included weight and height measurements and CF Questionnaire-Revised (CFQ-R).

RESULTS

Studies included 213 patients (aged ≤ 20 years, n = 105; aged > 20 years, n = 108). In patients ≤20 years, adjusted mean change from baseline to week 48 in body weight was 4.9 versus 2.2 kg (ivacaftor vs. placebo, p = 0.0008). At week 48, change from baseline in mean weight-for-age z-score was 0.29 versus -0.06 (p < 0.0001); change in mean BMI-for-age z-score was 0.26 versus -0.13 (p < 0.0001). In patients >20 years, adjusted mean change from baseline to week 48 in body weight was 2.7 versus -0.2 kg (p = 0.0003). Mean BMI change at week 48 was 0.9 versus -0.1 kg/m(2) (p = 0.0003). There was no linear correlation evident between changes in body weight and improvements in lung function or sweat chloride. Significant CFQ-R improvements were seen in perception of eating, body image, and sense of ability to gain weight.

CONCLUSIONS

Nutritional status improved following treatment with ivacaftor for 48 weeks.

Pancreatic Enzyme Replacement Therapy and Coefficient of Fat Absorption in Children and Adolescents With Cystic Fibrosis

OBJECTIVES

Pancreatic enzyme replacement therapy (PERT) is the proven therapy to substantially reduce fat malabsorption in patients with cystic fibrosis (CF). Few details of the daily practice regarding PERT and the resulting coefficient of fat absorption (CFA) are known. We therefore recorded the PERT and CFA in a large cohort of pancreatic insufficient pediatric patients with CF.

METHODS

We retrospectively studied 1719 completed 3-day dietary food records, including the pancreatic enzyme intake registrations, and 1373 CFA assessments of 224 patients with CF, ages 0-17 years. The clinical characteristics, PERT, expressed as an intake of lipase unit (LU) per gram of fat per day and LU per kilogram per day, and the CFA were described for the group as a whole and separately for those on enteral tube feeding. Cross-sectional relationship between the CFA and the LU per gram of fat per day and LU per kilogram per day were determined for each year of age. We also addressed the effect of the interventions done in patients with CFA outcomes <85%.

RESULTS

The LU per gram of fat per day was relatively stable throughout the age groups, whereas the LU per kilogram per day fell markedly with age. The median CFA in the age group 17 varied between 86% and 91%, however, with a CFA below 85% in 325 of 1373 (24%) of the measurements. No relationship was found between PERT and CFA. The patients with persistent CFA less than 85% had significant lower z scores weight for age and weight for height (P = 0.01) than those with CFA at least 85%.

CONCLUSIONS

In this study population, no correlation between an enzyme dosage and the degree of fat malabsorption was found; however, a CFA below 85% was found in 24% of the measurements.

Animal models of gastrointestinal and liver diseases. Animal models of cystic fibrosis: gastrointestinal, pancreatic, and hepatobiliary disease and pathophysiology

Multiple organ systems, including the gastrointestinal tract, pancreas, and hepatobiliary systems, are affected by cystic fibrosis (CF). Many of these changes begin early in life and are difficult to study in young CF patients. Recent development of novel CF animal models has expanded opportunities in the field to better understand CF pathogenesis and evaluate traditional and innovative therapeutics. In this review, we discuss manifestations of CF disease in gastrointestinal, pancreatic, and hepatobiliary systems of humans and animal models. We also compare the similarities and limitations of animal models and discuss future directions for modeling CF.

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.

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.

Recent advances in cystic fibrosis

Cystic fibrosis (CF) is an inherited chronic disease that remains a common cause of morbidity and mortality in affected patients, mostly in the young. A wealth of knowledge has been gained into the genetics, pathophysiology, and clinical manifestation of the disease. In parallel with these new insights into the disease, novel treatments have been developed or are under development that have had a major impact on quality of life and survival. Improvement in the delivery of care to patients in CF centers, using a team-based approach, and constant review of process, and by quality improvement projects, have also had an impact on outcomes in CF.

Liprotamase long-term safety and support of nutritional status in pancreatic-insufficient cystic fibrosis

OBJECTIVES

Patients with cystic fibrosis (CF) who have exocrine pancreatic insufficiency (EPI) require treatment with pancreatic enzyme replacement therapy (PERT) to maintain adequate nutrition and age-appropriate growth and weight gain. Liprotamase, a nonporcine, highly purified biotechnology-derived PERT, has demonstrated significant efficacy in fat and protein malabsorption in patients with EPI compared to placebo. This study of liprotamase is the first ever long-term trial of a PERT to evaluate safety and nutritional parameters.

METHODS

This phase III 12-month open-label trial assessed the safety, tolerability, and long-term nutritional effects of liprotamase treatment in patients with CF and EPI 7 years and older. All of the patients were required to discontinue their long-term use of porcine PERTs at the time of enrollment. Dosing started at 1 capsule of liprotamase (32,500 US Pharmacopoeia (USP) units crystallized cross-linked lipase, 25,000 USP units crystallized protease, and 3,750 USP units amorphous amylase) per meal or snack; dose could be increased based on protocol-defined parameters.

RESULTS

A total of 215 subjects were enrolled and 214 received at least 1 dose of liprotamase (mean 5.5 capsules per day). During the study period, height, weight, and body mass index z scores and lung function as measured by forced expiratory volume in 1 second were stable. There were no clinically meaningful changes in laboratory tests, including levels of fat-soluble vitamins. Liprotamase was well tolerated without any significant safety concerns. Adverse events, primarily gastrointestinal, led to treatment discontinuation for 36 subjects (16.8%), most within the first 3 months.

CONCLUSIONS

Treatment with a mean of 5.5 capsules of liprotamase per day, during meals and snacks, for up to 12 months was safe, well tolerated, and associated with age-appropriate growth and weight gain or weight maintenance in subjects with CF-related EPI.

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.

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.