Lt Col Reynolds
Urinalysis is used to screen for causes of secondary hypertension, and to look for damage to the kidneys as a result of untreated hypertension. Dr. Patel, can you tell us more about why a provider might order a urinalysis?

Dr. Patel
Absolutely, Dr. Reynolds. When the kidneys filter blood, they separate waste from the blood cells and proteins. The waste is sent on to the bladder as urine. By examining what is present in a patient’s urine, the provider can determine how well a patient’s kidneys are functioning.

A urinalysis consists of two parts: a chemical analysis and a microscopic analysis. In the chemical portion of a urinalysis, a dipstick is used to detect the presence or absence of certain compounds in the urine. The chemicals on the dipstick change colors when they come in contact with specific substances.

Two of the substances a dipstick can detect are protein and hemoglobin released from red blood cells. Normally, protein is too large to be filtered, so urine usually doesn’t contain any protein. Sometimes, however, untreated hypertension can cause damage to the kidneys. When this happens, the filtration system may leak, allowing protein and sometimes blood to enter the fluid that is filtered out to become urine. When blood or protein is found in the urine, it may indicate that damage due to high blood pressure has occurred. It’s important to note, however, that finding protein or blood in the urine does not necessarily mean that hypertension is the cause. These substances may be present in the urine as a result of other processes, and further tests will probably need to be done.

In the microscopic portion of a urinalysis, the urine sample is examined under a microscope. The microscope may reveal the presence of blood cells, cells from the kidney itself, or urine crystals that can be indicators of either kidney disease or damage to the kidney as a result of high blood pressure.