The influence of retrograde contrast medium on urinary cytodiagnosis: a preliminary report.

It has been recommended that before retrograde brushing of upper urinary tract lesions to diagnose malignancy the contrast medium should be washed away with saline because of possible cellular distortion. There were 21 paired specimens from 19 patients submitted for urinary cytodiagnosis. One specimen was a contrast medium wash, similar in pH and osmolality to urine, and the other a saline wash. Cellular detail was adequate for cytodiagnosis in 20 of the 21 contrast medium specimens. Of 7 specimens from patients with malignancy 3 were diagnosed correctly as malignant, 1 was classified as suspicious and 3 were falsely negative in the contrast wash group. Of the 3 falsely negative diagnoses 2 were changed to malignant when the paired saline wash specimens were examined. Urologists should not discard the contrast medium specimen prior to retrograde brushing but should send it along with a saline wash specimen for cytodiagnosis because the discarded contrast material and irrigant may have diagnostic cells.