By far the most commonly ordered test is the routine urinalysis, also known as R&M (routine and microscopic). This test is fast, inexpensive and may indicate liver and kidney diseases, diabetes, infection or a kidney stone. The routine urinalysis is done in three stages.
The first stage of urine testing looks at the general characteristics of the urine. The colour of the urine is recorded. There is also a report about whether the urine is clear or cloudy and the amount of acid is measured.
The next problem is learning whether the urine is more dilute or concentrated than normal. This is called testing the specific gravity. The specific gravity will show if a person has lost a lot of fluid and is dehydrated such as in vomiting and diarrhea. This test can help to detect if someone is unable to retain fluid such as in a pituitary gland condition known as diabetes insipidus, or if the kidneys have been damaged.
In the next stage, a small plastic strip with several different coloured squares on it is placed into the urine. Each square contains chemicals, which will react with a specific substance in the urine and change colour accordingly. By comparing the colours on the strip with a chart of 'normal' colours, the substances and their quantity in the urine can be detected. This strip routinely tests for glucose ketones, protein hemoglobin (blood) and leukocytes (white blood cells).
A good example of how the strip works is the testing for sugar (glucose) in the urine. Normally there is no glucose in urine. If there is a trace, the colour of the strip will change a small amount. If sugar is present in a large amount, the colour change will be dramatic. This may be the first clue that blood tests should be done to check for diabetes.
Further information about diabetes from urine testing could be the presence of ketones. Ketones occur when the body uses fat as an energy source. They may be found in the urine after a long time without food, but they may also indicate important problems with diabetes. Their presence is a warning that further investigation may be needed.
Protein is another substance that can be detected with a urine test. Normally protein is found in small amounts in the urine. Any larger quantity may mean one of many conditions which should be checked out. For instance, high levels of protein being passed in the urine may be caused by bladder and kidney infection, or by a problem of the kidneys, especially problems in the filtering system known as glomerulonephritis.
Blood in the urine may be nothing more than a spill-over from menstruation. It may be a sign of urinary infection, which is easily treated. However, the presence of blood can help in the diagnosis of a kidney stone. It may also be the first indication of a tumour in the urinary system. Finding blood in urine, which looks perfectly normal to the naked eye, is an excellent example of the sensitivity of the urine strip test.
White blood cells are also called leukocytes. When the dipstick is positive for leukocytes it may mean urinary infection. Vaginal infection can also cause white blood cells to spill over into the urine.
The third stage of the urine test involves looking at the urine under a microscope. Before this can be done, the solid parts of the urine, mainly cells, casts and crystals are concentrated by spinning a test tube of urine at high speed. This portion of the urine test is optional and may not be done if the first two steps are normal.
Red and white blood cells. Blood contains both red and white blood cells. These cells are almost always found in the urine, but only in small amounts. When red blood cells are found in increased amounts it may mean the same as blood detected by the strip test. White cells in higher-than-normal numbers often means a bladder infection or other urinary infection. A doctor can use this information to help decide whether or not to use antibiotics.
Cast and crystals. Both casts and crystals in the urine may mean a problem. Casts are microscopic substances produced in tiny filtering tubes of the kidney. Their presence in urine may show a problem with the kidney. Crystals are seen when there is an excess of substances such as uric acid in the urine. If there is too much of these substances in the urine they may form tiny crystals. The appearance of the crystal can allow it to be identified. Uric acid can be associated with gout and kidney stones.
The next time your doctor orders a urinalysis, don’t dismiss it as 'just a urine test.' There’s a lot to be learned from a little bit of urine.