Diagnostic Approach for Colovesical Fistula

Primary Imaging Recommendation

The American College of Radiology recommends MRI pelvis without and with IV contrast or CT pelvis with IV contrast as equivalent first-line imaging options for rectovesicular (colovesical) fistula, with CT being the practical first choice due to its wider availability and faster obtainment 1, 2
CT pelvis with intravenous contrast has a diagnostic sensitivity of 76.5% for fistula detection and 94.1% for defining the underlying etiology 1, 2

Cystography has a reported 90% detection rate for enterovesicular fistulas in older literature, but only 11-30% sensitivity in other series, and should only be used if CT/MRI is unavailable or findings are equivocal 3, 4
Contrast enema (barium or waterigli water-soluble) has a very poor sensitivity of only 20-50% detection rate for colovesical fistulas and is not recommended as first-line imaging 3, 4
Water-soluble contrast is preferred over barium to avoid peritoneal contamination and CT artifact 3, 4

The American College of Radiology suggests a diagnostic algorithm starting with CT pelvis with IV contrast, followed by MRI pelvis with and without IV gadolinium if CT is equivocal or contraindicated, and always adding colonoscopy to exclude malignancy as the underlying cause 1, 2

CT with intravenous contrast is the most sensitive imaging modality for detecting colovesical fistulas, with a diagnostic sensitivity of 76.5%, and can usually be diagnosed on contrast-enhanced CT based on enhancing tract(s) with or without gas extending from colon to bladder wall, associated focal bladder wall thickening, and presence of pneumaturia or fecaluria in clinical history, according to the American College of Radiology 5
CT cystography can provide additional information regarding size and location of the fistula for presurgical planning, as recommended by the American College of Radiology 6, 7

The diagnosis of colovesical fistula can be missed by not using appropriate contrast techniques during CT imaging, highlighting the importance of proper imaging protocols, according to the American College of Radiology 5
Relying solely on barium enema or contrast studies, which have lower sensitivity than CT, can lead to missed diagnoses, as noted by the American College of Radiology 6, 7