Abnormal Urine Evaluation
The evaluation of abnormal appearing urine begins with a history and physical exam.
The physical exam in someone with abnormal appearing urine is usually normal.
Testing is necessary to make the diagnosis of abnormal appearing urine.
Tests that may be used to evaluate abnormal appearing urine include:
Abnormal Urine Urinalysis
Urinalysis refers to tests that are performed on the urine.
A urinalysis should be performed on a clean urine specimen. A clean catch is a sample of urine that is obtained midstream through urination. Males should first clean the head of the penis prior to urinating. Women and girls need to wash the area between the vaginal folds with soapy water and then rinse thoroughly. After passing a small amount of urine into a toilet, the specimen is obtained from the middle of the urine stream. Only a few ounces are needed to perform this test.
In infants, a plastic urine collection bag can be used, but often produces a poor specimen. Follow cleansing instructions above prior to applying the urine collection bag. These bags stick to the skin using an adhesive, but need to be removed promptly after a specimen is obtained.
Sometimes a catheter specimen is best in:
Some medications can interfere with the interpretation of some aspects of this test. These include:
- B-complex vitamins
- Iron pills
Components of Urinalysis
The urinalysis can be divided into chemical testing and microscopic analysis. Many of these tests are performed with a single dipstick. This is a strip with multiple colorimetric tests that is dipped into the urine. Color changes on each test indicate the result.
Color and Clarity
This index can give information as to the patient's degree of hydration, or the possibility of infection. Concentrated or infected urine can be dark or cloudy. Many medications can influence the appearance of the urine. Jaundiced patients may have bilirubin in the urine.
Urine color can vary from almost colorless to dark yellow or amber. Fluid loss or reduced fluid intake is the most common cause for urine that is darker and more concentrated.
This indicator measures the relative concentration of the urine. With dehydration, healthy kidneys can concentrate the urine. This causes a high specific gravity. The specific gravity of pure water is 1.000.
The specific gravity is normally in the range of 1.006 and 1.030. The higher the number the more concentrated the specimen. In the morning, after hours without any food or water, the urine will be more concentrated, with a specific gravity greater than 1.025.
The pH index provides a measurement of the acidity or alkalinity of the urine. It can change as a result of dietary intake, medications, or through the abnormal functioning of the lungs or kidneys.
The normal pH varies from 4.6 to 8.0. A higher pH can occur right after eating a meal. Many medications can influence the urine pH. Low pH values suggest acidosis, which can occur in diabetes, poisonings, and serious infections.
Urine normally contains very little glucose. In diabetics, urine glucose levels become elevated when the blood sugar exceeds 140. Finding glucose in the urine will prompt an evaluation for diabetes and other disorders. Measurement of glucose in the urine is no longer an effective way to monitor diabetes.
Most healthy people have no glucose in their urine. The finding of very small amounts of glucose in the urine can be normal. Meals rich in carbohydrates can lead to increased urine glucose, even when the blood glucose is normal.
When there are insufficient carbohydrates available for energy, the body will break down fats to ketones. Ketones are easily detected in the urine. Starvation or protracted vomiting can give a positive urine ketone test. Ketones may also indicate poorly controlled diabetes.
Increased urine ketones occur in:
- Diabetic ketoacidosis
- Low carbohydrate weight loss diets
- Prolonged fever
- Protracted vomiting
- Severe stress
Protein may normally be present in the urine in small quantities. This usually occurs after strenuous exertion or with a prolonged fever. Persistent protein in the urine can indicate kidney disease, congestive heart failure, or kidney infection. Preeclampsia in pregnant females results in protein in the urine. Urine protein is often monitored in diabetic patients who are at risk for kidney disease.
Urine protein is normally negative. Occasionally trace amounts of protein may be seen.
The urine is tested for the presence of hemoglobin. This is the oxygen-carrying molecule found in blood. This is a dipstick test.
Another method for detecting blood in the urine is to study the urine specimen under the microscope. Using this approach detects the presence of red blood cells in the urine.
Conditions that may cause blood in the urine:
- Bladder cancer
- Bladder polyps
- Contamination with menstrual blood in females
- Injury to the kidney or genitourinary tract
- Kidney disease
- Kidney stones
- Renal cell carcinoma
- Rhabdomyolysis (crushing injuries and electrical injuries)
- Strenuous exercise (normal finding)
- Urinary tract infection
Bilirubin is a by-product of hemoglobin metabolism. It is normally present in bile and in the blood in low levels, but not in the urine. Bilirubin in the urine may be due to hepatitis, gallstones, or tumors affecting the bile duct. Bilirubin is normally not present in the urine.
Urobilinogen is a by-product of bilirubin. It is formed by the action of bacteria in the intestines. When this chemical level is elevated, it can indicate hemolytic anemia, liver damage, or a drug side effect. Lower than normal values are more useful. This can indicate blockage of bile flow to the intestine, which may occur with gallstones.
This test detects the presence of white blood cells with a dipstick test. Leukocyte esterase testing is an excellent screen for urinary tract infections.
A technician uses a microscope to look for abnormal quantities of any of the following:
- Red blood cells
- White blood cells
- Miscellaneous findings include hair, yeast, parasites, and sperm.
Continue to Abnormal Urine Treatment
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- Rich MW. Porphyria cutanea tarda. Don't forget to look at the urine. Postgrad Med. 1999 Apr;105(4):208-10, 213-4.