Case Presentation: A 23-year-old man with cystic fibrosis presented to the Emergency Department with a two-day history of gradual, persistent, right sided abdominal pain associated with dark, tarry stools. He was afebrile with unremarkable vital signs. Exam was notable for generalized abdominal tenderness most noticeable in the right lower quadrant and a normal rectal exam. Computed tomography of the abdomen and pelvis was obtained and showed a dilated appendix with trace inflammatory changes as well as thickening of the colonic mucosa and terminal ileum. He was admitted to the Surgery team for further care given concern for acute appendicitis and underwent laparoscopic appendectomy. The hospitalist team was engaged to assist with management of cystic fibrosis after the appendectomy. In partnership with the patient’s outpatient team, prior imaging was reviewed and it was determined that the appendix had been intermittently inflamed in the past but had not required intervention. He was encouraged to continue utilizing his pulmonary regimen for cystic fibrosis. Post-operatively, the patient was discharged home with oxycodone-acetaminophen and famotidine. Surgical pathology later returned and was found to be consistent with a simple mucocele without signs of appendicitis.

Discussion: The differential for abdominal pain is often broad. In people with cystic fibrosis, distal intestinal obstruction syndrome (DIOS) occurs when the lumen of the bowel is partially or fully occluded by intestinal contents. The pathogenesis is not fully understood though is postulated to be related to dehydration, changes in diet, dysmotility and insufficient pancreatic enzyme activity. DIOS can manifest as a triad of cramping abdominal pain, a right lower quadrant mass, and accumulation of stool in the distal small intestine and right colon. As seen in this patient’s presentation, DIOS can mimic appendicitis given the location of pain and the presence of inflammatory changes in the bowel. DIOS should also be differentiated from chronic constipation though they can co-occur. Management includes correction of fluid and electrolyte abnormalities and osmotic laxatives to encourage stool output. Surgical intervention is only indicated in patients with peritoneal signs who may need laparotomy and decompression. After acute treatment, prophylaxis with chronic administration of osmotic laxatives, optimization of pancreatic enzyme treatment, and adequate hydration are the mainstays of long-term prevention.

Conclusions: Hospitalists should have distal intestinal obstruction syndrome on their differential in patient with cystic fibrosis who present with abdominal pain. Management is generally supportive with the goal of relieving the current obstruction and preventing future obstruction.