For urinalysis, an array of chemical and microscopic tests is used to examine a urine specimen. The results can aid in the diagnosis of kidney disorders, urinary tract infections, and metabolic diseases that result in the excretion of abnormal breakdown products in the urine. The following tests are commonly included:
Appearance, color, and odor can provide clues to various disorders. For example, cloudy urine may be caused by the presence of pus, red blood cells, or bacteria. High levels of bilirubin (the main pigment in bile) may color the urine dark yellow, indicating possible liver disease.
Specific gravity is a measure of how dilute or concentrated the urine is; abnormal levels can occur with kidney disease, dehydration, and other conditions.
- pH level indicates the relative acidity or alkalinity of the urine. For example, a highly alkaline urine pH may be associated with certain bacteria that cause urinary tract infections.
- Protein is not normally found in the urine in large quantities. The presence of protein in the urine usually signifies that there is a structural abnormality, and may indicate a range of problems including kidney dysfunction.
- Glucose, when present in excessive amounts in the urine, usually indicates diabetes mellitus.
- Ketones, which are breakdown products of fat metabolism, may be found in the urine during starvation, after alcohol intoxication, and in people with poorly controlled diabetes.
- Bilirubin, a byproduct of the hemoglobin in red blood cells, indicates possible liver disease when found in the urine.
- Nitrites suggest a urinary tract infection, because many bacteria produce an enzyme that converts urinary nitrates to nitrites.
- Crystals may appear in normal urine or in samples that have not been examined immediately, or may indicate a kidney stone or another problem. The type of crystal varies with the disease and the pH of the urine.
- Casts—plugs that form when a protein made in the renal tubules combines with cells or cellular debris—may sometimes be seen in the urine. Different types of casts (such as hyaline, granular, fatty, waxy, epithelial, red cell, and white cell casts) are linked with particular disorders.
- White blood cells in the urine suggest urinary tract inflammation, particularly in the kidney or bladder.
- Red blood cells in the urine signal bleeding within the genitourinary tract. Diseases affecting the bladder, ureters, or urethra are the most common causes.
Purpose of the Urinalysis
- To check for signs of kidney or urinary tract disease
- To aid in the detection of metabolic or systemic diseases not related to kidney disorders
- To help diagnose endocrine disorders
Who Performs Urinalysis
- You will usually be asked to collect the urine sample yourself.
Special Concerns about Urinalysis
- Dietary factors, some medications, and strenuous exercise may interfere with interpretation of results.
- Recent injection with an x-ray contrast dye may alter the specific gravity, cause false-positive protein levels, and lead to crystals in the urine.
- Vaginal secretions in the urine can affect protein levels and cause false-positive results for white blood cells.
Before the Urinalysis
- Avoid strenuous exercise before the test.
- Inform your doctor about any medications you are currently taking. If a specific drug could alter the results, you may be advised to stop taking it before the test.
What You Experience during Urinalysis
- A standard urine sample is collected in a sterile container.
Risks and Complications of Urinalysis
After the Urinalysis
- Resume taking any medications withheld before the test.
Results of Urinalysis
- The urine sample is frequently analyzed in your doctor’s office with special chemical strips that react with substances in the urine and change color. The examiner then interprets the resulting color changes. A more detailed analysis, including microscopic examination, may also be done in-office or at a pathology laboratory.
- Your doctor will review the findings for evidence of kidney disease, urinary tract infection, and diabetes or another metabolic abnormality.
- Urinalysis is often a first step in assessing potential kidney or metabolic disorders. In many cases, additional tests may be needed to obtain a definitive diagnosis.
- If an abnormality is found and the doctor can make a definitive diagnosis, appropriate treatment will begin, depending on the problem.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media