Why is a Urinalysis Used for Medical Diagnosis?

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Urinalysis is used to test for several conditions. Symptoms that occur may be as a result of a urinary tract infection (UTI), a disorder of the kidney or another medical condition. A urinalysis helps in determining what the root cause of the symptoms may be. It is also used in testing for drugs and alcohol and for testing whether or not a woman is pregnant.

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The kidneys are mainly responsible for producing urine. Urine is composed of several wastes and by-products that are present in the body. Our kidneys filter out the waste materials and fluids from the blood, which are then passed down to the urine. Minerals, toxins and other substances are also filtered by the kidneys, eventually being passed out in the urine. The kidneys help in regulating the water content of the body and conserve proteins as well as electrolytes which the body uses. A urine test is a good measure of your overall health.

Collecting a urine sample for testing is fairly easy. The sample can be collected either at home, at a facility where testing is conducted or at your doctor's office. Concentration levels in the first sample, early in the morning, are much higher and allow for detecting any abnormalities present in the urine with greater ease. Even though the first sample is considered the most ideal, urine can be collected at any time. A sample can be collected by first letting out a portion of the urine in the toilet, then collecting an ounce or two of urine in a container and finally letting the remaining portion out in the toilet. A sample collected in this manner is called a "midstream collection" or "clean catch". Making sure that the genitalia is clean before collecting a sample ensures that no bodily fluids enter the urine and interfere with the test results. Taking the sample to a laboratory or a doctor's office for testing should be done within an hour after collection. If the delay is longer than an hour, the sample should be refrigerated.

Once the sample is submitted, it is tested and analysed for any abnormalities. There are several different types of urine tests; however, a general analysis involves a visual inspection of the urine followed by a chemical inspection. Abnormalities, if present, are further examined by microscopic inspection of the urine. Your doctor may also order a microscopic inspection based on the test results, if he feels that further examination needs to be conducted. We will now look at these three phases of urinalysis in further detail and describe the various components that are looked at to aid in a medical diagnosis based on urinalysis.

Visual inspection of the urine, involves checking the urine's color, clarity and odor. We will look at each one of these briefly.

• Color: The color of the urine is affected by the kinds of foods you eat, medications and certain infections. Normal urine usually has a color of pale to yellow. Brown urine can be caused by the presence of bile pigments. Dehydration is generally the cause for dark yellow urine, whereas red urine is caused by either blood in the urine due to hematuria or sometimes by eating certain foods such as blackberries, rhubarb and beets.

• Clarity: Normal urine is usually clear. The presence of sperm or bacteria can make the urine appear cloudy. Other factors why the urine maybe cloudy is due to conditions, such as, phosphaturia, pyuria, chyluria, lipiduria and hyperoxaluria. Hyperunicosuria, caused due to food that is rich in purines, can also cause cloudy urine.

• Odor: Under normal conditions, a person's urine has a bit of a "nutty" odor to it. The normal odor of urine is described as uronoid and can be very strong in specimens that are concentrated. One condition that can change the odor of urine is diabetic ketoacidosis, in which the smell of urine is sweet or fruity. Bladder retention can cause the urine to have an ammoniacal odor. Cystine decomposition can cause a sulfuric acid smell in the urine, whereas gastrointestinal-bladder fistulas can cause a fecal smell. Odor is also affected by medications, UTI's, and certain foods, such as, asparagus.

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