Genitourinary Radiology > Bladder > Intravesical or Interstitial Air > Bladder Fistulas


Bladder Fistulas

The most common causes of intravesical air include bladder catheterization or instrumentation. Vesicoenteric fistulas may be difficult to image - only 30-60% are seen with cystography and barium enema. Iatrogenic causes, diverticulitis, carcinoma, and regional enteritis or Crohn's disease may lead to vesicoenteric fistulas.

VCUG with steep oblique or full lateral views is the best imaging modality, with findings that include air within the bladder, focal mural irregularity or extrinisic mass effect. CT with oral and rectal contrast demonstrates air within bladder, focal bladder wall thickening >2mm, contiguous bowel wall thickening >3mm, and presence of air-containing, paravesical soft-tissue mass. Radiography of centrifuged urine looking for traces of barium (Bourne test) may be performed.

Causes of vesicovaginal fistula include iatrogenic, cervical or bladder carcinoma, obstetric injury, radiation, and foreign body; it presents clinically with continuous urinary incontinence.

Axial CT scan through the pelvis shows an air fluid level (arrows) in the bladder (b). In the abscense of instrumentation, considerations include fistula to a viscus or to the vagina or to the skin. Infection is a less likely possibility (emphysematous cystitis).

Plain film radiograph of the pelvis shows an air lucency in the bladder (arrows) in the same patient as above.

Axial CT scan through the pelvis following instillation of contrast into the bladder shows a connection (arrows) between the patient's vagina (v) and bladder (b). This is consistent with vesicovaginal fistula.

Cystogram in the lateral projection in the same patient as above shows with contrast instillation into the bladder (b) via Foley catheter, the vagina (v) also fills with contrast confirming vesicovaginal fistula.



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