Figure 8. Sigmoidovesical fistula secondary to diverticulitis. CT cystogram shows an air-fluid level in the bladder and contrast material in the colon, findings that suggest the diagnosis. Associated active diverticulitis is noted with bowel wall thickening (arrow). The affected section of the sigmoid colon is contiguous to the left posterior bladder wall, which appears focally thickened with obliteration of the fascial plane between the colon and the bladder. Air bubbles are noted along this connecting tract (arrowheads), thus highlighting the fistula.