Gastrointestinal disease in Cystic Fibrosis (CF) is caused by defective chloride and bicarbonate transport in intestinal cells leading to reduced intraluminal fluidity, increased mucous viscosity and consequently development of intestinal inflammation, dysbiosis and often times dysmotility. This triad is also referred to as the "CF gut". A diagnosis is mainly based on clinical observation and treatment is often times decided empirically. This review of the literature should provide CF caregivers with some tools to identify intestinal inflammation, dysbiosis and dysmotility as possible cause for their patient's gastrointestinal complaints and provide an overview of our current approach to its management.

Objectives-The "gold standard" for the diagnosis of fat malabsorption, the 72 hour fat balance study, requires a three day collection to generate a coefficient of fat absorption (CFA). We hypothesized that, a new test using behenic acid (behenate test) as a nonabsorbable lipid marker may provide a facile means to assess fat absorption. The study proposed to answer two questions: 1) whether the "behenate test" correlated with the "gold standard" and 2) whether the CFA improved when taking pancreatic enzymes during meals instead of prior to them.Methods-The study compared the "behenate test" with the gold standard in 15 cystic fibrosis patients during three arms which require 3-4 day hospitalizations: one taking pancreatic enzymes prior to meals, one taking pancreatic enzymes during meals, and one off of pancreatic enzymes.Results-The mean CFA was 78.3% when pancreatic enzymes were taken during meals and 80.4% when pancreatic enzymes were taken prior to meals. Correlation between the CFA and the "behenate test" for collections during all 3 arms was r 2 = 0.219 (p= 0.001). Conclusion-1)Timing of ingestion of pancreatic enzymes does not significantly alter the CFA. 2) Although the CFA correlates with the "behenate test", the correlation is not robust enough to justify its replacement of the "gold standard." It is unclear whether the poor correlation between tests relates to intermeal variability in fat excretion,or other factors; however the "behenate test" may be suitable as a screening test for detection of fat malabsorption.

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INTRODUCTION:Evidence about specific carbohydrate diet (SCD) for inflammatory bowel disease (IBD) is limited. We conducted 54 single-subject, double-crossover N-of-1 trials comparing SCD with a modified SCD (MSCD) and comparing each with the participant's baseline, usual diet (UD).METHODS:Across 19 sites, we recruited patients aged 7–18 years with IBD and active inflammation. Following a 2-week baseline (UD), patients were randomized to 1 of 2 sequences of 4 alternating 8-week SCD and MSCD periods. Outcomes included fecal calprotectin and patient-reported symptoms. We report posterior probabilities from Bayesian models comparing diets.RESULTS:Twenty-one (39%) participants completed the trial, 9 (17%) completed a single crossover, and 24 (44%) withdrew. Withdrawal or early completion occurred commonly (lack of response [n = 11], adverse events [n = 11], and not desiring to continue [n = 6]). SCD and MSCD performed similarly for most individuals. On average, there was <1% probability of a clinically meaningful difference in IBD symptoms between SCD and MSCD. The average treatment difference was −0.3 (95% credible interval −1.2, 0.75). There was no significant difference in the ratio of fecal calprotectin geometric means comparing SCD and MSCD (0.77, 95% credible interval 0.51, 1.10). Some individuals had improvement in symptoms and fecal calprotectin compared with their UD, whereas others did not.DISCUSSION:SCD and MSCD did not consistently improve symptoms or inflammation, although some individuals may have benefited. However, there are inherent difficulties in examining dietary changes that complicate study design and ultimately conclusions regarding effectiveness.