One of the most commonly performed tests before surgery or during a hospitalization is a urinalysis. This test is performed by examining urine to analyze the content and chemical makeup. While it is typically done prior to surgery to identify any kidney issues that may be present, a urinalysis may be performed in your doctor's office if a kidney infection, urinary tract infection, or some other issue is suspected.
The term urinalysis is a general one meaning to examine urine, but there are different types of tests that can be performed. Urine can be examined to determine if the individual has used prescription or illicit drugs recently.
The urinalysis is not diagnostic, meaning the results don't diagnose a disease, but rather can direct further testing to determine the exact nature of a problem. For example, a urinalysis cannot be used to diagnose diabetes, but if the results showed both elevated glucose and ketone levels, a test for diabetes would be the next logical step.
Obtaining a Urine Sample
A urine sample can be collected by having the patient collect the sample themselves, typically by urinating into a sterile container, a process called a "clean catch." Typically, the patient is asked to start urinating, and then once the stream has started and the first few seconds of flow have been discarded, the sample is collected.
You may be given a cleansing wipe to use prior to collecting the sample. This is done to minimize the risk of contamination from your skin.
If the patient has a Foley catheter, the nurse typically collects the sample from the tubing prior to the urine reaching the collection bag.
Urinalysis Testing Phase One: Visual Examination
Checking the color and clarity of the urine sample is the first test performed. The urine sample is visually examined for color, with "yellow," "straw," or "nearly colorless" being typical normal values. Abnormal colors are possible: orange can be a side effect of a prescription medication, brown and pink may indicate the presence of blood, and dark yellow can mean dehydration.
Urinalysis Testing Phase Two: Chemical Testing
pH: This test looks at the acid level in the urine. Significantly high or low values may indicate an issue with the kidneys.
Specific Gravity: This portion of the test determines how concentrated the urine is. If the patient is dehydrated, for example, the specific gravity will be high. If the person is very well-hydrated, a lower result is expected. Diabetes insipidus, a condition where the body excretes large amounts of urine, will result in a very low specific gravity.
Protein: Finding protein in the urine is not a normal finding. Seriously elevated levels may indicate that there is a problem with kidney function.
Glucose: Finding glucose in the urine is not a normal finding. Typically, this is found in patients with diabetes.
Ketones: Finding ketones in the urine is not a normal finding. Typically, diabetes is the cause of ketones in the urine. The finding of ketones will typically result in testing for diabetes, or it may indicate a need for better glucose control in a diabetic patient.
Leukocytes: Leukocytes in the urine typically indicate a past or current infection in the urinary tract.
Blood: The presence of blood in the urine is an abnormal finding. However, it is not possible to determine the cause of the bleeding without further testing. Common causes include infection, trauma, kidney stones, cancer, surgery on an area of the urinary tract, kidney disease, trauma related to the insertion of a urinary catheter, and many other causes.
hCG: This is a pregnancy test. In male patients, the result is typically reported as "not applicable," while women will have a positive or negative result. A urinalysis may or may not include a pregnancy test, depending on what a standard urine screening is at the facility where the test is performed and what the physician has ordered.
Urinalysis Testing Phase Three: Microscopic Exam
A small amount of the urine sample, typically a few drops, is placed on a slide and examined under a microscope. This is done to determine if there are cells in the urine that indicate the presence of bleeding, infection or contamination.
White Blood Cells (WBCs): Very few or no WBCs should be present in the urine. Significant numbers typically indicate the presence of infection.
Red Blood Cells (RBCs): Like white blood cells, there should be very few or no red blood cells found in the urine.
Epithelials: Epithelial cells should not be present in a urine specimen. The most common cause of epithelial cells in a sample is improper collection of the urine, meaning that the sterile specimen has been contaminated. If contamination is ruled out and epithelial cells are again found in a second test on an additional urine sample, further testing will be required to explain the presence of these cells.
Bacteria: The presence of bacteria may indicate an infection or contamination of the sample.
Casts: A cast, which may be referred to as a red, white, or hyaline cast, typically looks like a small clump of egg white suspended in the urine. The presence of casts is not normal and may be suggestive of kidney issues.
Urinalysis. Medline Plus. Accessed June, 2012. http://www.nlm.nih.gov/medlineplus/ency/article/003579.htm