Review article: treatment of perianal fistulizing Crohn's disease.

Fistulizing Crohn's disease can involve the bowel, but is more commonly seen in the perianal region. In acute perianal Crohn's disease, perianal lesions are manifestations of disease activity and are frequently treated concomitantly with bowel lesions. Spontaneous resolution occurs in up to 50% of patients. Fistulae are secondary lesions that may progress to destruction of the sphincter apparatus necessitating proctectomy after years of suffering. The control of sepsis is the first objective. The drainage of abscesses and the placement of setons are essential steps in treatment. Disease severity can be readily assessed by examination under anaesthesia and by magnetic resonance imaging. Endoscopic ultrasonography is sensitive, but is hampered by the necessary introduction of a large instrument into an often narrowed anorectum. Antibiotics, especially metronidazole and ciprofloxacin, are useful short-term therapies to decrease or stop drainage, but relapse is immediate on discontinuation. Immunosuppression with azathioprine (2.5 mg/kg per day) or mercaptopurine (1.5 mg/kg per day) is effective, but slow and often incomplete. The management of perianal fistulizing disease resistant to standard treatment has greatly improved with the introduction of the anti-tumour necrosis factor-alpha antibody, infliximab. The complete arrest of the drainage of fistulae is obtained in 46% of patients 10 weeks after the administration of 5-10 mg/kg of infliximab at weeks 0, 2 and 6 and, on average, lasts for 12 weeks. A treatment algorithm for fistulizing Crohn's disease must therefore involve the early and optimal use of immunosuppression and of infliximab. Medical and surgical co-operation is also critical to achieve the best possible outcome.