The overall incidence of vesicovaginal fistula is unknown but was reported to be 2.11 per 100 births in Nigeria .
The tract is lined by squamous epithelium at the vaginal end and transitional epithelium at the bladder end, often with focal ulceration and fibrosis.
There are a number of causes including
- prolonged obstructed labor (most common in developing countries)
- surgery, e.g. hysterectomy (most common in developed countries)
- pelvic malignancy (e.g. bladder carcinoma, endometrial carcinoma)
- uterine rupture
A fluoroscopic cystogram is a commonly-used method for evaluating this type of fistula. Contrast is injected into the bladder through a Foley catheter and the fistulous tract is outlined. A number of oblique and lateral projections are needed to determine the location.
Gas-fluid levels are seen within the vagina which disappear after 3-4 micturitions, whereas gas bubbles are seen within the bladder for up to one week.
The fistula may be seen as a hypodense area with excretion of contrast into the vagina on delayed CECT images. The tract may be visible if a CT cystogram is performed.
CT, in addition, may provide details regarding the cause of the fistula, such as an adjacent pelvic mass or bowel thickening .
- T1: tract is centrally hypointense (fluid)
- T2: tract is hyperintense with gas bubbles seen as low signal intensities
- T1 C+ (Gd): peripheral enhancement on contrast