Urine cytology is commonly used to screen for bladder cancer in patients who have hematuria as well as to monitor for recurrences in patients who are being treated for bladder cancer. Overall, urine cytology is able to detect 40% to 60% of bladder cancers, but the ability of cytology to detect a tumor varies depending on the grade, stage, and location of the tumor. In low-grade, low-stage tumors, cytology will detect only 25% to 40% of the tumors.
It will perform better as the grade and stage of the tumor increase, with the best detection rate being for carcinoma in situ. Cytology detects approximately 90% of cases of carcinoma in situ. Cytology is less effective when there are other conditions present, such as urinary tract infections, bladder stones, kidney stones, or previous treatments with BCG or intravesical chemotherapy. These conditions all cause inflammation or irritation of the bladder cells, which makes the cytology difficult to interpret.