From the Guidelines
Contrast-enhanced CT is the best imaging modality for diagnosing a colovesical fistula.
Key Points
- Colovesical fistula can usually be diagnosed at contrast-enhanced CT alone without intracavitary contrast material based on enhancing tract(s) with or without gas extending from the colon to the bladder wall, with or without associated focal bladder wall thickening 1.
- CT cystography can provide additional information regarding the size and location of the colovesical fistula in presurgical planning in some cases, but it is not usually helpful for the initial evaluation of colovesical fistula 1.
- Some studies suggest that CT cystography can accurately detect and characterize the colovesical fistula in greater than 80% of patients, especially in those who present with symptoms of urinary tract infection, fecaluria, or pneumaturia 1.
- MRI is also effective in diagnosing colovesical fistula, particularly when repeat imaging is an issue, due to its multiplanar imaging capability and high soft-tissue resolution 1.
- However, contrast-enhanced CT is generally considered the first-line imaging modality due to its high sensitivity and specificity in detecting the fistula and its associated complications.
- Other imaging modalities like IVU, US, and upper gastrointestinal or small-bowel follow-through have very low yields for fistula diagnosis 1.
From the Research
Imaging Modalities for Diagnosing Colovesical Fistula
- Computed Tomography (CT) is a highly effective imaging modality for diagnosing colovesical fistulae, as it can readily detect air within the bladder and assess the extent of pericolonic inflammation 2, 3, 4, 5.
- CT with rectal contrast is considered the most accurate imaging modality for diagnosing colovesical fistulae 3.
- Barium enema is also a useful diagnostic tool, particularly for detecting stricture formation and fistulous tracts 4.
- Cystoscopy is a highly accurate test for detecting fistulae, with a detection rate of 46.2% 4.
- Colonoscopy is the most reliable means of excluding a colonic malignancy and can detect underlying aetiology 4, 5.
- MRI is a useful imaging modality for diagnosing colovesical fistulae, with characteristic morphological patterns that can aid in diagnosis 6.
Characteristics of Colovesical Fistulae on Imaging
- On MRI, colovesical fistulae can be classified into three morphological patterns: an intervening abscess between the bowel wall and bladder wall, a visible track between the affected bowel and bladder, and a complete loss of fat plane between the affected bladder and bowel wall 6.
- CT can detect air within the bladder and assess the extent of pericolonic inflammation, making it a valuable tool for preoperative surgical planning and postoperative follow-up 2, 3, 4, 5.