Fistula formation is one of the complications of diverticulitis, accounting for up to 20 percent of surgically treated cases of diverticular disease . Diverticulitis in western countries usually involves the sigmoid colon, and fistulization most frequently arises from this segment. The major types of fistulas are colovesical fistulas (65 percent, (image 1)) and colovaginal fistulas (25 percent), followed by coloenteric and colouterine fistulas . However, a fistula can form to whichever organ the inflammatory process tracks, and has been described in many unexpected sites (image 2) .
Diverticulitis is also the most common cause of a colovesical fistula, accounting for 40 to 90 percent of cases . Although diverticulitis occurs with a slight female predominance, colovesical fistulas secondary to diverticulitis has a distinct (2 to 3:1) male predominance [1,4]. It is likely that the uterus protects the bladder from the inflamed sigmoid; this hypothesis is supported by the observation that the majority of women with colovesical or colovaginal fistulas have had a previous hysterectomy [1,3,5].
Colovesical fistulas illustrate the features of most diverticular fistulas. Only about one-half of patients have a history of diverticulitis; in the remainder, diverticulosis is diagnosed when the fistula becomes clinically evident . Affected patients often give a history of passage of stool and gas via the involved organ. Thus, common symptoms with a colovesical fistula include pneumaturia, dysuria, or irritative symptoms, and fecaluria [1,3,4]. Other symptoms occurring in fewer than 50 percent of patients are crampy abdominal pain, diarrhea, hematuria, and passage of urine per rectum [1,4].
Physical examination is frequently unremarkable. The urinalysis is invariably abnormal and cultures reveal the nonspecific finding of polymicrobial growth.
These findings occurring together are suggestive of a colovesical fistula, but not of the etiology. Causes other than diverticulitis include Crohn's colitis and carcinoma.