How long is urinary cytology abnormal after flexible cystoscopy?

OBJECTIVE: To examine the urinary cytological changes caused by flexible cystoscopy and provide clinical guidelines for a reliable time interval for urinary cytological examination after flexible cystoscopy. PATIENTS AND METHODS: Forty-eight patients attending for flexible cystoscopy were recruited into the study. Each patient was asked to provide eight urine samples before, immediately after and at 1, 2, 7, 14 and 28 days after cystoscopy. Cytospin preparations of the urine samples were made and slides stained using the Papanicolaou stain. Cytology was analysed while unaware of sample origin, by three different cytopathologists. RESULTS: The cytological changes were characterized by a striking increase in cellularity immediately after flexible cystoscopy, mostly accounted for by urothelial cells. Consistent morphological changes included the formation of 'columnar' cells, papillary clusters, increased nucleo-cytoplasmic ratio and nuclear atypia. These changes were transient, with most disappearing within a day of flexible cystoscopy. CONCLUSIONS: There are cytological changes, on voided urine cytology, after flexible cystoscopy but they were transient, and urine sent more than a day after flexible cystoscopy should be free from artefactual change caused by instrumentation. These results suggest that clinicians sending urine for cytological analysis should provide information about the nature and timing of any endoscopy so as to avoid false-positive interpretations of urine cytology by the cytopathologist.