Clinical Pathology

The kidneys are responsible for the formation and excretion of urine, the principal way the body eliminates waste products and excess fluid. Urine excretion provides a means of regulating the body’s state of hydration and the blood concentration of ions such as sodium, potassium, and other small molecules. Three processes are involved in urine formation:

• Filtration of waste products, salts, and excess fluid from the blood by glomeruli

• Tubular reabsorption of water and solutes from the glomerular filtrate

• Tubular secretion of ions and molecules into the urine 

Although urine production is a primary function of the kidneys, the kidneys also have other functions, such as the production of  hormones necessary for strong bones, blood pressure control, and red blood cell production.

Tests such as those performed in the routine urinalysis provide an indication of an individual’s metabolism and general state of health. An understanding of kidney function and urine composition helps laboratory personnel understand and interpret routine urinalysis results.