Imaging description

When performing contrast-enhanced CT of the pelvis, physiologic excretion of urine into the urinary bladder can cause the spurious appearance of a filling defect which should not be confused with a bladder mass.

The pseudomass appearance in the bladder due to urinary jets can be caused by either an ureteral contrast jet entering the bladder that contains mostly hypodense non-opacified urine (Figure 75.1) or a non-opacified urine jet entering the contrast-filled bladder (Figure 75.2). The latter can mimic a hypodense mass.

Since most CT of the abdomen and pelvis scans in emergency departments are performed with intravenous contrast, the more commonly observed pattern is that of a radiodense jet (Figure 75.1). Depending on the timing of the scan, variable mixtures of excreted contrast and non-opacified urine may result, which can be mistaken for bladder masses. Recognition of pseudomass artifact is important and can easily be obviated by obtaining delayed scans through the bladder or ultrasonography of the bladder.