Teaching Case

At a routine Check-up, a 71-year-old female with a history of diverticular disease and kidney transplantation complained about gas during voiding. She had no other significant physical complaints. Urine analysis showed an abundant amount of fibres. Subsequently a CT-scan was ordered.

A CT-scan in portal venous phase with rectal contrast was performed. Many diverticula are present throughout the colon, in particular in the sigmoid region with concomitant intestinal wall thickening. A transplanted kidney resides in the right iliac fossa with the ureter anastomosed to the roof of the bladder. An extensive amount of air is seen within the bladder and a smaller amount in the pyelum of the transplant kidney (fig. 1). No contrast leakage can be seen between the urinary tract and the colon. There is however a close relationship between the sigmoid and the bladder roof with wall thickening of both organs (fig. 2). Furthermore, there appears to be a fistula between the sigmoid and the ureter (fig. 3). Both a ureterocolic and a colovesical fistula where suggested in the report. Subsequently the patient underwent surgery.

Colonic diverticula are sac-like outpouchings of the intestinal wall. They develop at weak points where the vasa recta penetrate the circular muscle layer of the colon. The presence of colonic diverticula, or diverticulosis is common in western countries with a prevalence of 50% among individuals aged 60, and 70% at the age of 80 [1]. The most common location is in the sigmoid colon. It is estimated that 5% of the patients with diverticulosis will develop diverticulitis [2], most frequently with a mild course. However, diverticulitis can also be complicated by abscess, perforation and fistula formation. Fistula formation can occur in 14% of the cases of complicated diverticulitis, with colovesical fistula as the most frequent type [3]. Ureterocolic fistulas secondary to diverticular disease, on the other hand, are rare with only 10 cases reported in literature [4].

Patients may present with symptoms related to an acute episode of diverticulitis, such as nausea, vomiting and abdominal pain. With regard to the fistulous connection between colon and urinary system, symptoms are usually mild. Patients may complain about pneumaturia, fecaluria, dysuria and urgency. Urine analysis reveals abundant bacteria and traces of food.

Although the clinical history is highly suggestive of the presence of a fistula, additional imaging is recommended. CT scanning is the imaging modality of choice because of its high accuracy [5]. Scanning protocols should include an unenhanced scan, unhenhanced with rectal contrast and an enhanced scan in portal venous phase. Findings include colonic diverticula, air in the urinary system, thickened bladder wall abutting the colon or a visible fistula with or without contrast leakage. These elements can be seen on the CT scan of the presented case. Besides confirming the presence of a colovesical fistula, a CT scan provides an overview that can be useful for depicting unexpected lesions and exact anatomic relations for surgical planning.

In general the treatment of choice is surgical and is aimed at resection of the diseased bowel and closure of the fistula. In selected cases a non-operative strategy may be reasonable [6].

In conclusion, fistula formation is not an uncommon sequela of diverticular disease. Although the clinical history can be nearly pathognomonic for the existence of such a fistula, additional imaging is important. Especially cross-sectional imaging such as CT scanning provides an accurate anatomic overview and can depict rare entities as illustrated in this case. Such information is vital for treatment.