The urinary tract lining is constantly renewing itself; as new cells grow, the dead ones are shed and carried out of the body in urine. A cytology test is a non-invasive diagnostic that takes advantage of this process. By looking for abnormal, cancerous cells, the test can confirm a cancer diagnosis or determine whether ongoing treatment for the urinary cancers (kidney, ureter, prostrate, and urethra) has been effective. In rare cases, cytology may also be used to identify the presence of viral cells, such as the cytomegalovirus (a normally harmless virus that can cause problems in infants and people who are immunocompromised).
Cytology Test—When to Get One
A physician may recommend a cytology test when patients have blood in their urine (hematuria) and at least one other risk factor, including a family history of cancer or symptoms such as stomach pain, back pain, unexplained weight loss, and testicular swelling (all of which are associated with urinary tract cancers).
Urine cytology is only one of many tests used to confirm cancer, but it is particularly good for diagnosing larger-cell and rapidly reproducing cancers because those very properties make them easier to detect in a urine sample. Slowly developing cancer or smaller-cell cancers, such as small-cell carcinomas, on the other hand, may not be as easy to identify.
Patients must wait until later in the day to provide a urine specimen since cancerous cells can break down overnight, making morning urine an inaccurate measurement of urinary tract lining cells.
To obtain a specimen, patients can urinate into a sterile container, or a physician can insert a urinary catheter to access the bladder. The latter method is useful for people who are incontinent or who produce little urine, such as patients with chronic kidney failure. While effective, this approach carries an increased risk of infections because a catheter might carry bacteria into the urinary tract.
The urine sample is sent to a lab, where it's evaluated with a test (fluorescent in situ hybridization) that examines the genetic material of cells in the urine and can detect the mutations and abnormalities common in cancerous cells. A pathologist also examines the cells under a microscope.
While each laboratory may interpret results differently, commonly used evaluations include:
- Negative: Cancerous cells were not found.
- Atypical: Abnormal cells are present, but they are not necessarily cancerous. (This result can indicate inflammation in the urinary tract.)
- Suspicious: Cancerous cells may be present.
- Positive: Cancerous cells were present.
- Unsatisfactory: Pathologists could not properly interpret the cells.
When cytology results are inconclusive, a physician may recommend repeating the test several times to more confidently confirm or rule out a diagnosis.
Urine Cytology. (2011). American Urological Association.