By Kelly Evans-Hullinger, MD
Urinalysis, or testing of the urine, has ancient origins dating back to the time of Hippocrates and beyond. Although we have evolved in our methodology of studying the urine and our understanding of the meaning of its characteristics, we do still rely on urinalysis in making clinical diagnoses frequently in medicine.
In centuries past, the tools of urinalysis were blunt and primarily involved human senses of sight, smell, and taste (yes, taste). Ancient physicians noted that sediment in the urine often correlated with fever, the sediment in question probably being white blood cells. Bubbles in the urine might portend kidney disease, which we know to be true if the bubbles are caused by excessive protein in the urine. And diabetes mellitus was generally known to be present in cases of excessive, sweet tasting urine.
In modern laboratories, we test urine using chemical assays and by looking at urine sediment under a microscope. What might we be looking for when we ask our patients to provide a urine sample?
Red blood cells can be present in a variety of conditions, including trauma to the urinary tract such as from infection or kidney stones, tumors of the urologic tract, and diseases affecting the microscopic structures of the kidney, among other things. White blood cells are more specific to urinary tract infection, though they can be seen in some other types of kidney injury as well.
We look routinely for protein in the urine of patients with diabetes or known kidney disease. Protein in the urine is typically the first sign of kidney damage from chronic diseases like diabetes. And the amount of protein in the urine of a patient with chronic kidney disease can help us understand prognosis and whether certain medications are working. Glucose is found in the urine if a person has very high blood glucose (or if they are taking certain medications). Numerous other chemical tests of the urine can help us to diagnose selective medical conditions.
As a physician in the modern era, luckily I have never tasted my patients’ urine like Hippocrates and his cohorts would have. But I do use urinalysis every day to help me diagnose and care for my patients.
Kelly Evans-Hullinger, M.D. is part of The Prairie Doc® team of physicians and currently practices internal medicine in Brookings, South Dakota.