Wednesday, January 25, 2017
Wisdom Wednesday: The Urine Analysis
This is the last blog of my series on yearly laboratory testing. The previous blogs have all been about analysis of the blood. Today we focus on the urine.
Urine is a waste product that can provide a lot of information about metabolism in the body. It’s much like analyzing the exhaust from an automobile to see how well the engine is running.
The specific gravity measures the weight of the urine as compared to water. The normal range is 1.005 – 1.030. Pure water is 1.000. Levels below 1.005 indicate hyperhidrosis, above 1.030 dehydration.
The pH measures the relative acidity or alkalinity. The normal range is 5.0 – 7.5. Again, water is the reference with a neutral pH of 7.0. If the urine pH is above 7.5 it is too alkaline. If it is below 5.0, then it’s too acidic. Some bacterial infections like an acid environment, some like it alkaline. The use of cranberry juice for a UTI (urinary tract infection) is appropriate when the pH is high as the cranberry juice will lower the pH. However, use when the pH is below 5.0 will just support the acid-loving infection.
Normally the urine is clear in appearance and yellow in color. The presence of blood, WBCs, nitrates, or other particles can cloud the urine or change the color. If the urine is a dark yellow and the specific gravity is high suspect dehydration. You should monitor your own urine color for signs of dehydration as well.
There are a variety of chemical compounds that are evaluated routinely. A trace of protein is acceptable but there should be no glucose, ketones, or occult blood evident. Small amounts of urobilinogen are also acceptable. Nitrates are the result of bacterial degradation and also should not be seen.
If all of the parameters noted above are normal then the urine analysis is complete. However, if enough abnormalities are found, then a microscopic analysis is performed. This looks for bacteria, cells, and crystals.
The presence of bacterial obviously indicates an infection and a culture is typically run. This attempt to grow the bacteria, then expose it to various drugs takes three days. However, it can readily determine what specific bacteria is infecting the body and what drugs the organism is susceptible to or resistant from. Even if you are given a broad spectrum antibiotic after the initial UA, it’s a good idea to run the culture just in case the bacteria is resistant to that specific antibiotic. Then you have some recourse if the antibiotic is ineffective.
The urinary tract will sluff epithelial cells from the lining in response to inflammation and infection. However, if renal cells or casts are detected they are coming from the kidney itself rather than a simple UTI.
Crystals are common with a variety of metabolic imbalances. Many times these crystals will form kidney stones. The chemical composition of the crystals is vitally important to proper treatment. Uric acid crystals are common in gout. Calcium oxalate crystals are often due to improper metabolism of vitamin C. Although these two crystals are quite common, there are many other types of crystals that can occur in the urinary system.
The Bottom Line:
The urine analysis is often overlooked. It’s kind of like panning for gold. Just because you don’t see gold nuggets in every pan doesn’t mean there isn’t gold there. I will often repeat a first morning, mid-stream catch urine analysis every couple of weeks if we are actively treating some imbalance in kidney or urine function.