Colonic fistulas are uncommon. They are frequently external but also occur internally to a variety of organs. External fistulas invariably are caused by a complication or are the result of a surgical procedure, such as a leaking anastomosis or incision and drainage of an abscess resulting from underlying pathology. The most common disease process implicated in the spontaneous development of fistulas from the colon is diverticular disease. Less commonly, we encounter fistulas caused by Crohn's disease or a malignancy of the colon. Of 412 patients with diverticular disease treated at the Cleveland Clinic from 1960 to 1986, 84 (20.4%) had internal fistulas.<sup>10 Woods R.J., Lavery I.C., Fazio V.W. , e al. Internal fistulas in diverticular disease Dis Colon Rectum 1988 ;  51 : 591-596  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> Eight had multiple fistulas. The majority (65%) were colovesical. The next most common was colovaginal (25%), and the remainder were coloenteric or colouterine. In another series of patients with colocutaneous fistulas in diverticular disease,<sup>8 Steel M., Deveney C., Burchell M. Diagnosis and management of colovesical fistulas Dis Colon Rectum 1979 ;  22 : 27-30

Cliccare qui per andare alla sezione Riferimenti</sup> 88 of 93 fistulas followed surgery. This compares with only 5 of 93 who developed a fistula in the absence of surgery on the colon. Ten of the patients with complicated fistulas were also diagnosed with Crohn's disease.