Imaging features of colovesical fistulae on MRI

Abstract

Objectives: MRI is routinely used in the investigation of colovesical fistulae at our institute. Several papers have alluded to its usefulness in achieving the diagnosis; however, there is a paucity of literature on its imaging findings. Our objective was to quantify the MRI characteristics of these fistulae.

Methods: We selected all cases over a 4-year period with a final clinical diagnosis of colovesical fistula which had been investigated with MRI. The MRI scans were reviewed in a consensus fashion by two consultant uroradiologists. Their MRI features were quantified.

Results: There were 40 cases of colovesical fistulae. On MRI, the fistula morphology consistently fell into three patterns. The most common pattern (71%) demonstrated an intervening abscess between the bowel wall and bladder wall. The second pattern (15%) had a visible track between the affected bowel and bladder. The third pattern (13%) was a complete loss of fat plane between the affected bladder and bowel wall. MRI correctly determined the underlying aetiology in 63% of cases.

Conclusions: MRI is a useful imaging modality in the diagnosis of colovesical fistulae. The fistulae appear to have three characteristic morphological patterns that may aid future diagnoses of colovesical fistulae. To the authors' knowledge, this is the first publication of the MRI findings in colovesical fistulae.

Figure 1

Sagittal T₂ weighted image of a track between the dome of the bladder and sigmoid colon.

Figure 2

Coronal T₂ weighted image of an intervening abscess (arrow) between the affected bladder and sigmoid colon.

Figure 3

Sagittal T₂ weighted image demonstrates complete loss of the fat plane between the bladder dome and sigmoid colon (arrow). There is also focal disruption of the low T₂ signal bladder muscularis. Dependent debris is seen along the posterior wall of the bladder.