Reversed contrast-urine levels in urinary bladder: CT findings.

Contrast-urine levels are routinely seen in contrast-enhanced computed tomography (CT) of the pelvis with contrast-opacified urine in the bottom and unopacified urine in the top. We encountered four cases in which contrast-urine levels were reversed. The reversal of the contrast-urine level was probably caused by high specific gravity of the preexisting urine in the bladder due to infectious debris or mucous threads in the urine.