1About one-third of all patients with Crohn’s disease experience the development of fistulae. Fistulae represent a kind of short circuit connection between individual bowel loops or may form between the bowel and other organs, such as the urinary bladder, vagina or the skin. The most common site affected by fistula formation is the tissue surrounding the anus. In this area, the fistula forms a connection between the rectum and the skin surrounding the anus. The development of fistulae is associated with certain complications, including the formation of abscesses (encapsulated collections of pus).2

When the formation of fistulae is suspected, the physician will perform certain diagnostic procedures (see figure “Perianal Fistulae”). Depending on location, these include radiologic examinations such as CT or MRI, proctoscopy and/or endosonography. The therapy of fistulae depends on their location and associated complications. Because of the associated inflammatory reaction, treatment may begin with the administration of antibiotics. In certain cases, however, it may be necessary to surgically remove the fistula or the bowel segment from which the fistula originates. This is often recommended in cases of fistulae that form between two bowel loops (see figure “Fistula opening in a patient…”) or when complicated by extensive abscess formation. In the longer term, most patients will ultimately require either surgical or immunosuppressive (e.g. azathioprine) to definitively close the fistulae. A new treatment method involves the suppression of the messenger substance, tumor necrosis factor (TNF). This, however, usually results in only temporary closure of the fistula and the method should be reserved for patients who do not respond adequately to the above-described medical or surgical treatments. To date, however, no totally satisfactory method for treating fistulae has been devised.