Although the inciting pathology is usually intestinal, the presenting symptoms are often urinary in nature. The most common presenting complaints are pneumaturia reported in 57% to 91% and fecaluria in 42% to 76%. Recurrent urinary tract infections, irritative voiding symptoms, and abdominal pain are also common, whereas passage of urine per rectum is not
typical (1,2,3,4). Physical signs suggestive of enterovesical fistulas are often subtle or absent but may include a palpable mass or abdominal tenderness with or without local peritonitis. Associated physical findings are more commonly associated with fistulas secondary to inflammatory bowel disease (5). In patients with rectal disease, a rectal abnormality or tenderness may be present. Urinalysis usually reveals pyuria with or without hematuria, and urine cultures are positive in the majority of patients with the most common growth patterns being multiple organisms or isolated Escherichia coli (2).

Given the symptomatic nature of enterovesical and colovesical fistulas, the diagnosis is typically a clinical one. The goal of assessment is not only to diagnose and localize the fistula but also to identify and develop a treatment strategy for the underlying intestinal or urinary pathology. Radiographic assessment is used as an adjunct and may assist with anatomic localization and surgical planning. Traditionally, barium enema has been used as a first study, but more recent series have demonstrated fistula identification rates of only 20% to 42% (1,2,3,4). Other imaging modalities including computerized tomography (CT) and magnetic resonance imaging (MRI) have mixed results in the literature in terms of diagnosis. However, although axial imaging may fail to demonstrate the fistula, it may aid in surgical planning and identification of etiology and may be diagnostic based on the associated indirect findings of the fistula including air in the bladder or focal bladder or bowel wall thickening. In our institution, the use of CT cystography has replaced other anatomic and functional studies including standard cystography, CT urogram, and MRI.

Functional studies have been described for the diagnosis of enterovesical fistula and include the charcoal test, urinary or rectal visualization of administered dyes, the poppy seed test in which the urine is evaluated for orally consumed poppy seeds, or the Bourne test where urine is examined for barium following a nondiagnostic barium enema. Although the sensitivities of these tests may approach 100% in the literature (4), they are seldom performed because they often fail to provide anatomic detail and the diagnosis of fistula is usually self-evident based on the clinical picture.

Direct visualization with colonoscopy and cystoscopy is a key component of the analysis. Colonoscopy rarely identifies a fistula tract but is recommended for its importance in evaluating the etiology and extent of the intestinal disease (1,2,3,4). Cystoscopy is the most common abnormal investigation. Although fistula identification rates are reported to be from 10% to 60% (1,3), up to 90% of cystoscopies may show indirect evidence of the fistula including bullous edema or inflammatory bladder wall abnormalities (2).