Fistulas are most common with which of the following bowel disorders?
A. Crohn’s disease
B. Diverticulitis
C. Diverticulosis
D. Ulcerative colitis
Correct Answer: A. Crohn’s disease
The lesions of Crohn’s disease are transmural; that is, they involve all thickness of the bowel. These lesions may perforate the bowel wall, forming fistulas with adjacent structures. Crohn’s disease can progress from an initially mild to moderate inflammatory condition to severe penetrating (fistulization) and/or stricturing disease. The initial lesion starts out as an infiltrate around an intestinal crypt. This goes on to develop ulceration first in the superficial mucosa and involves deeper layers.
Option B: Fistulas don’t develop in diverticulitis. Diverticulitis is the result of microscopic and macroscopic perforations of the diverticular wall. Previously, practitioners thought that obstruction of colonic diverticulum with fecaliths led to increased pressure within the diverticulum and subsequent perforation. They now theorized that increased luminal pressure is due to food particles that lead to erosion of the diverticular wall.
Option C: Diverticula occurs in weaker portions of the colonic wall where the vasa recta infiltrates the circular muscular layer. The vast majority of colonic diverticula are typically “false” diverticula, which are mucosa and submucosa herniating through a defect or weakness in the muscularis layer, covered externally only by serosa.
Option D: The ulcers that occur in the submucosal and mucosal layers of the intestine in ulcerative colitis usually don’t progress to fistula formation as in Crohn’s disease. Colonoscopy or proctosigmoidoscopy might reveal loss of typical vascular pattern, granularity, friability, and ulceration which involve the distal rectum and proceed proximally in a symmetric, continuous, and circumferential pattern.
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