Crohn’s disease: penetrating type

Abbreviations

Introduction

A fistula is defined as a pathologic channel connecting two or more epithelialized surfaces. While abdominal imaging, such as computed tomography (CT), magnetic resonance imaging (MRI) and small bowel series, and enterclysis, is the main stay for the diagnosis of fistula, endoscopy can provide important information on the primary and secondary openings in the bowel and status of inflammation around the orifices. Endoscopy may be combined with examination under anesthesia for the diagnosis of fistulas, especially perianal fistulae. Approximately 14%–50% of the patients with Crohn’s disease (CD) present or eventually present with fistulae . Perianal fistula or abscess can also occur in patients with ulcerative colitis . Furthermore, fistula can develop after surgery for inflammatory bowel disease (IBD), with main cause being anastomotic leaks. Therefore fistulas in IBD can be primary (i.e., disease-associated) or secondary (e.g., anastomotic or suture-line leak associated). Fistulizing CD with the formation of abscess has been considered the ultimate adverse complication of the disease. While fistula can be the initial presentation of patients, the formation is preceded by transmural inflammation and stricture formation in the downstream bowel segment. We believe, “no inflammation, no stricture; and no stricture, no fistula.” For example, ileosigmoid fistula (ISF) is often associated with terminal ileum or ileocecal valve (ICV) strictures ( Fig. 6.1 ).

CD-associated perianal fistula is discussed in a separate chapter ( Chapter 7 : Endoscopic evaluation of perianal Crohn’s disease). The classification of CD-associated fistula is proposed ( Table 6.1 ).