Urinalysis

What is a urinalysis?

A urinalysis is used to evaluate the urine for various abnormalities, including the presence of increased numbers of white/red blood cells with or without bacteria (suggesting infection), abnormal epithelial cells (which may indicate a bladder or other urinary tract tumor), high levels of glucose (which may suggest diabetes or rare kidney diseases), urinary crystals, and protein (which may indicate certain systemic diseases, high blood pressure, and/or issues with the kidney filtering system).  Other parameters such as urine specific gravity (USG) and urine pH tell the clinician a lot about the patient, including whether or not the kidneys are capable of concentrating urine appropriately. 

How is urine collected?

Urine can be collected in a number of ways.  The simplest way to obtain a urine sample is by the “free-catch” method, where the patient urinates and a sample is collected in a cup.  This technique is used most frequently when urine is being screened during general health checks (ie when no particular abnormalities are expected) and for evaluation of urine concentration.  Other common methods of collection include cystocentesis (sticking a small gauge needle into the bladder and aspirating urine into a syringe) or catheterization (inserting a tube through the urethra – the tube that connects the bladder to the outside world - and aspirating urine with a syringe).  Both techniques are utilized when a sterile urine sample is needed, such as when a urinary tract infection is suspected and/or urine culture/sensitivity (to confirm infection and determine the appropriate course of antibiotics) is required.  Although more invasive than the “free-catch” method, this method generally takes less than 5-10 minutes and causes minimal discomfort.  While bleeding secondary to either procedure is possible, this is a very rare occurrence.

How is a urinalysis useful for cancer patients?

Evaluation of urine is a useful diagnostic test when certain bladder or urinary tract tumors are suspected in a patient.  In a moderate percentage of patients with bladder tumors, urine will contain cancer cells that can be visualized under the microscope and lead to a definitive diagnosis.  In addition, cancer patients (especially those receiving steroids or chemotherapy) may be immunocompromised, so evaluation for infection every so often may be indicated in certain cases.  Since certain chemotherapeutic agents are excreted through the kidneys, knowing urine specific gravity is very important, as it provides information about the kidney’s ability to concentrate urine appropriately.  Patients with diminished urine concentrating ability (or kidney disease) may require reduced doses of certain drugs excreted by the kidneys to prevent adverse side effects.