Hypocellular bladder wash specimens and their clinical significance

Bladder wash flow cytometry specimens containing less than 1,000 cells were defined as hypocellular. Between June 1981 and December 1990, 5,676 bladder wash flow cytometry specimens were collected, of which 142 (2.5%) were deemed hypocellular. Of the 132 evaluable patients with hypocellular specimens 34 (30%) had documented evidence of carcinoma compared to 52% for the entire population. Among the 34 patients 30 had transitional cell carcinoma, of which 12 were carcinoma in situ, 9 stage Ta or T1 and 9 stage T2 or greater. Thus, there was no obvious relationship between stage or grade of carcinoma versus probability of a hypocellular specimen. Differences in irrigation techniques of different urologists in the operating room using general anesthesia versus catheter and cystoscopic irrigation in the outpatient clinic are discussed as possible explanations for the hypocellular specimens.