Increased abnormal urothelial cells in voided urine following excretory urography

A prospective study of 45 consecutive patients scheduled for excretory urography demonstrated a statistically significant increase in the proportion of abnormal urothelial cells, including pseudomalignant cells, recovered in the urine between three hours and seven days after urography. The total number of urothelial cells recovered in the urine did not increase at any time. The Millipore filter imprint technique, which allows semiquantitative examination of urothelial cells from urine, is discussed.