Perianal Crohn's disease: Overview
Article Outline
Crohn's disease (CD) is a chronic inflammatory disorder that can affect any part of the gastrointestinal tract from the mouth to the anus. The disease is characterized by transmural inflammation that can be complicated by the development of fibrotic strictures, perforation, abscess formation, and fistulization.
A variety of perianal manifestations may occur in patients with CD, including perianal skin lesions (anal sin tags, haemorrhoids), anal canal lesions (anal fissures, anal ulcers, anorectal strictures), perianal fistulas and abscesses, rectovaginal fistulas, and cancer [1], [2]. Perianal fistulas may arise from inflamed or infected anal glands (fistula-in-ano) and/or penetration of fissures or ulcers of the rectum or anal canal [3].
Perianal fistulas cause significant morbidity and diminish patients’ quality of life. Consequences of perianal fistulas include perianal drainage, pain, abscess formation, dyschezia, dyspareunia, and faecal incontinence.
The cumulative frequency of perianal fistulas in patients with CD has been reported to range from 14% to 38% in patients evaluated at referral centres, and from 17% to 28% in patients undergoing surgery for CD, while it is 36% in patients participating in clinical trials, and 13% in children and adolescents at referral centres [4]. Two population-based studies have estimated the cumulative incidence of perianal fistulas in patients with CD. Hellers et al. [5] reported that the cumulative incidence of perianal fistulas in Stockholm County, Sweden, between 1955 and 1974 was 23%. Similarly, Schwartz et al. [6] showed recently that the cumulative incidence of fistulizing CD in Olmsted County, Minnesota, between 1970 and 1993 was 38%. Perianal fistula occurred in 12% of with patients with ileal CD, 15% of patients with ileocolonic disease, 41% of patients with colonic disease with rectal sparing, and 92% of patients with colonic disease and rectal involvement. Moreover, anal fissure or perianal fistula or abscess precedes or presents simultaneously with the diagnosis of intestinal disease in 36–81% of patients with CD who develop perianal disease [5], [6], while a small proportion of patients may have only isolated perianal disease [7].
The pathogenesis of perianal fistulas is unknown. Two mechanisms have been hypothesized. The first suggests that fistulas result from the elongation of deep penetrating ulcers in the anus or rectum. Over time, faeces collect in these ulcers, and the pressure of defecation forces the faecal matter into the subcutaneous tissue, extending the ulcer and creating a fistula. The second suggests that fistulas result from an anal gland abscess that serves as the point of origin for a fistula tract. From the intersphincteric space, a fistula can penetrate through the external anal sphincter and track downward to the skin or upward in the intersphincteric space, leading to the different types of perianal fistulas commonly seen [2], [8].
The identification and classification of perianal fistulas in CD is essential to providing safe and effective treatment for this patient population. Severine Vermeire et al., from University of Leuven (Belgium), in their review, analyse current classifications of any perianal form of CD, evaluating the wide range of perianal manifestations in patients with CD: skin tags and haemorrhoids, fissures, ulcers, abscesses, fistulas, stenoses or cancer. A more commonly used clinical classification distinguishes between simple and complex fistulas as proposed by the American Gastroenterological Association (AGA) [4].
An understanding of the natural history of perianal CD is critical in predicting fistulizing complications and managing these often complex patients. Steven B Ingle et al. of the Mayo Clinic College of Medicine (Rochester, Minnesota, USA) focus their review on the clinical course of CD, which is more aggressive in patients with perianal involvement; established risk factors for perianal disease, including genetic susceptibility, and possible evolution to perianal cancer, a rare complication of perianal disease, which must be suspected when lesions persist despite therapy.
Accurate diagnosis and classification of perianal disease is crucial before and during treatment to plan an adequate approach for each patient and to avoid irreversible functional consequences. In this context, our review, from “L. Sacco” University Hospital of Milan (Italy), evaluates the role of the several available imaging modalities in assessing diagnosis, classification and monitoring of CD perianal fistulas. These modalities include pelvic magnetic resonance imaging, anorectal endoscopic ultrasonography, transcutaneous perianal ultrasound, fistulography and computed tomography.
The pharmaceutical agents with definite or potential efficacy for treating patients with perianal CD include antibiotics, conventional immunosuppressive agents (azathioprine and 6-mercaptopurine, cyclosporine, tacrolimus, and methotrexate), and biological therapies (infliximab and other anti-TNF agents). In their paper, Leah Griggs et al. of the Vanderbilt University Medical Center (Nashville, TN, USA) review current data regarding medical options for treatment of fistulizing CD, distinguishing between simple and complex perianal disease, and emphasizing the need to combine medical and surgical therapy which, if initiated early in the course of the disease, could be associated with better outcomes and reduced morbidity.
For the majority of patients with perianal CD, the goal of surgical therapy is to control perianal sepsis through abscess drainage and to control fistulas through the placement of setons. The surgical management of perianal CD is complex, with a wide range of operations being described. B. Singh et al. of the John Radcliffe Hospital, Oxford (UK) consider all the possible surgical options for patients with perianal CD, outlining once again that management of perianal CD relies on accurate evaluation of the condition, and balancing the benefits of both surgical and medical approaches.
This series of papers is intended to provide a general view of perianal CD and not to be an exhaustive text-book on this important topic. However, it highlights several relevant areas useful in everyday clinical practice for patients suffering from perianal CD.
Conflict of interest statement
None declared.
References
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- . Occurrence and outcome after primary treatment of anal fistulae in Crohn's disease. Gut. 1980;21:525–527
- The natural history of fistulizing Crohn's disease in Olmsted County, Minnesota. Gastroenterology. 2002;122:875–880
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- . The pathogenesis and treatment of fistula-in-ano. Br Med J. 1961;1:463–469
PII: S1590-8658(07)00468-9
doi:10.1016/j.dld.2007.07.152
© 2007 Published by Elsevier Inc.
