Diagnosis and treatment of fistulising Crohn's disease.

A fistula is defined as a pathological connection between the intestine and an inner (bladder or other intestine) or outer (vagina or skin) epithelial surface. Fistulas are discovered in up to 25% of all Crohn's disease patients during long-term follow-up examinations. Most are perianal fistulas, and these may be classified as simple or complex. The initial investigation of perianal fistulas includes imaging (MRI of the pelvis and rectum), examination under anaesthesia (EUA) with digital imaging, endoscopy, probing and anal ultrasound. Non-perianal fistulas require contrast imaging and/or CT/MRI for complete anatomical definition. Any abscess should be drained, and the disease extent throughout the entire gastrointestinal tract should be evaluated. Treatment goals for perianal fistulas include reduced fistula secretion or none, evaluated by clinical examination; the absence of abscesses; and patient satisfaction. MR imaging is required to demonstrate definitive fistula closure. Fistulotomy is considered for simple perianal fistulas. In complex perianal fistulas, antibiotics and azathioprine or 6-mercaptopurine, which are often combined with a loose seton, constitute the first-line medical therapy. In cases with persistent secretion, infliximab at 5 mg/kg is given at weeks 0, 2, and 6 and subsequently every 8 weeks. Adalimumab may improve fistula response in both infliximab-naïve patients and following infliximab treatment failure. Local therapy with fibrin glue or fistula plugs is rarely effective. Definitive surgical closure of perianal fistulas using an advancement flap may be attempted, but this procedure is associated with a high risk of relapse. Colostomy and proctectomy are the ultimate surgical treatment options for fistulas. Intestinal resection is almost always needed for the closure of symptomatic non-perianal fistulas.