Important causes of chronic gastrointestinal symptoms in individuals with cystic fibrosis

Cause of symptoms	Mechanism	Typical presentation	Evaluation
Gastroesophageal reflux disease (GERD)	Lung hyperinflation, medications that reduce LES pressure, delayed gastric emptying. May be associated with constipation and/or generalized dysmotility.	Heartburn, acid brash, increased cough not due to other causes.	Empiric trial of acid-suppressing medication, exclude other causes of symptoms*^¶.
Obstipation/constipation	Abnormal intestinal secretions, dehydrated GI tract, dysmotility, pancreatic insufficiency. Constipation may contribute to GERD by delaying gastric emptying.	Flatulence, poor appetite, stool mass in LLQ. Constipation often occurs in CF despite daily stooling. Difficulty evacuating stool is rare.	History and physical examination; empiric treatment. Abdominal radiograph (if performed) shows stool mass throughout the colon.
Distal intestinal obstruction syndrome (DIOS)	Inspissated intestinal contents in the ileocecal area, causing complete or incomplete intestinal obstruction.	Acute or subacute onset of abdominal pain and distension with or without vomiting; stool mass in RLQ.	Abdominal radiograph shows stool mass, especially in the RLQ. Often co-occurs with constipation.
Small intestine bacterial overgrowth (SIBO)	Bacteria in the small intestine cause enterocyte damage and deconjugation of bile salts, causing malabsorption.	Bloating, flatulence, abdominal pain, watery diarrhea, dyspepsia, and weight loss.	Breath hydrogen and methane test, or empiric trial of metronidazole or other anti-SIBO antibiotics.
Cystic fibrosis-related diabetes (CFRD)	Diabetes is primarily due to impaired insulin secretion; may worsen with pulmonary exacerbations. CFRD may be complicated by neuropathy, which contributes to gastrointestinal dysmotility.	Weight loss, declining pulmonary function, especially in adolescents or young adults.	Oral glucose tolerance test^Δ.

LES: lower esophageal sphincter; GI: gastrointestinal; LLQ: left lower quadrant of the abdomen; CF: cystic fibrosis; RLQ: right lower quadrant of the abdomen; MII: multichannel intraluminal impedance; PERT: pancreatic enzyme replacement therapy.
* For suspected GERD, esophageal monitoring (pH probe or MII testing) may be useful in selected cases but has limited value in predicting treatment outcomes. Contrast radiography (eg, barium swallow) is not useful for the diagnosis of GERD, due to low specificity and sensitivity (refer to UpToDate topic review on diagnosis of GERD).
¶ Most patients with CF are on acid-suppressing medications to optimize the effectiveness of PERT. Therefore, GERD and esophagitis can be difficult to diagnose, and an empiric trial of acid suppression may not be possible.
Δ Hemoglobin A1c has low sensitivity for CFRD and should not be used to screen for this disorder.

Courtesy of Drucy Borowitz, MD.

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Important causes of chronic gastrointestinal symptoms in individuals with cystic fibrosis