Perianal Fistulas in Patients With Crohn's Disease, Part 1: Current Medical Management

Abstract

Despite significant advances in the treatment of luminal inflammatory bowel disease, the treatment of perianal fistulas remains a clinical challenge. Perianal fistulas are traditionally described using the Parks classification based on their relationship to the external and internal anal sphincters. Traditional therapy for perianal fistulas focuses on antibiotics such as metronidazole or ciprofloxacin. However, medical management has expanded over the years to include immunomodulators and, most recently, biologic agents. Newer techniques such as intrafistulous biologic injections are also being explored as potentially effective treatments for patients with fistulizing disease. Here, in the first of a 2-part series on perianal fistulas in patients with Crohn's disease, we discuss the anatomy and classification of perianal fistulas as well as current medical therapies, including antibiotics, immunomodulators, biologic agents, and novel therapeutic agents. The second part of the series will focus on the surgical modalities that are available for patients with perianal fistulas in addition to novel endoscopic techniques and future therapies that are being investigated for the treatment of fistulizing Crohn's disease.

Keywords: Crohn’s disease; Perianal disease; biologic agents; fistula; immunomodulators.

Figure 1.

A diagram of the rectal and anal canal anatomy demonstrates the internal and external anal sphincters as well as the levator ani muscle.

Figure 2.

The Parks classification of perianal fistulas illustrates a superficial fistula, intersphincteric fistula (type 1), transsphincteric fistula (type 2), suprasphincteric fistula (type 3), and extrasphincteric fistula (type 4) in relation to the internal and external anal sphincter muscles. A revised classification from the American Gastroenterological Association Technical Review Panel defines perianal fistulas as simple or complex.