Urine cytology is a non-invasive laboratory test that examines cells shed from the lining of the urinary tract and collected in a urine sample. A specialized physician, known as a cytopathologist, analyzes these cells under a microscope to look for abnormalities. The test focuses on urothelial cells, which form the inner layer of the bladder, ureters, renal pelvis, and urethra. It serves as a tool for screening and diagnosis by identifying cellular changes that indicate disease.
The Primary Goal of Urine Cytology
The test is primarily ordered to screen for and monitor urothelial carcinoma, cancer originating in the lining of the urinary tract, most frequently the bladder. Physicians recommend this procedure for patients experiencing unexplained hematuria (blood in the urine), a symptom of urinary tract cancer. The pathologist looks for changes in cellular structure, such as an enlarged or irregular nucleus, hallmarks of malignant or pre-cancerous conditions.
Urine cytology plays a significant role in the surveillance of individuals previously treated for bladder cancer. Regular testing helps monitor for recurrence, allowing for early intervention if abnormal cells are detected. The test is effective at identifying high-grade tumors, which shed distinctly abnormal cells into the urine. However, it is less sensitive for detecting low-grade tumors, whose cells often appear closer to normal.
Preparing and Submitting the Sample
The most common method for obtaining a sample is voided urine, provided by the patient into a sterile cup. A clean-catch technique is required to avoid contamination from the genital area and ensure the collected cells are suitable for examination. Patients must avoid collecting the first urine of the day (the first morning void) because cells that have remained in the bladder overnight can degrade, making them difficult to analyze accurately.
Instead, patients are instructed to provide a “second void” or a mid-morning sample, often after drinking fluids to encourage cell shedding. Samples may also be obtained via instrumentation, such as a bladder washing performed during a cystoscopy. This involves introducing and withdrawing a saline solution from the bladder to collect a concentrated population of cells directly from the lining. Catheterization, using a narrow tube inserted through the urethra, is another method to collect a sample directly from the bladder or upper urinary tract.
Decoding the Pathologist’s Report
The final report uses specific terminology to classify the cellular findings, guiding patient care. A “Negative for high-grade urothelial carcinoma” result is reassuring, indicating no malignant or highly suspicious cells were identified. Conversely, a “Positive” or “Malignant” diagnosis confirms that cells with clear features of cancer were present.
A result labeled “Atypical” means the cells show unusual features but are not definitively cancerous; these changes can be caused by inflammation or infection rather than malignancy. The term “Suspicious” carries a higher concern, suggesting the cells strongly resemble cancer but lack the necessary features for a definite positive diagnosis. The Paris System for Reporting Urinary Cytology provides standardized categories for these findings, helping to reduce variability between laboratories.
An “Unsatisfactory” result means the sample contained too few cells or the cells were too degraded for a reliable diagnosis, necessitating a repeat collection. Because urine cytology has limitations (particularly with low-grade tumors), an abnormal result often prompts further, more invasive testing, such as a cystoscopy, where a doctor visually inspects the bladder lining. The results are always interpreted alongside the patient’s medical history and other diagnostic information to determine the appropriate course of action.