The kidneys perform several important functions that preserve life. These functions include regulating blood pressure, filtering wastes from the blood, producing urine and maintaining normal fluid and electrolyte levels. When kidney function declines, the kidneys cannot perform these functions. This causes abnormal levels of fluid, potassium and other substances to accumulate in the bloodstream.
Potassium Regulation
The kidneys filter wastes out of the blood and excrete them from the body in the urine. Filtration occurs in the nephrons, which consist of tubules and a glomerulus. The glomerulus keeps cells and normal proteins in the circulatory system, and filters wastes and excess water out of the blood and into the urine. During this process, the kidneys return electrolytes like sodium and potassium to the bloodstream. This process regulates the amount of potassium and other substances in the body.
Kidney Dysfunction
Traumatic injury, exposure to toxic chemicals or the development of several kidney disorders results in damage to the filtering units of the kidneys. When this damage occurs, the kidneys do not filter wastes efficiently, and waste products build up in the blood. As waste products accumulate, the kidneys do not regulate electrolyte levels properly. This results in high levels of potassium in the blood, also known as hyperkalemia.
Identification
Medical professionals use the basic metabolic panel blood test to identify high potassium levels. This test measures the amounts of sodium, potassium, glucose, blood urea nitrogen (BUN), creatinine, calcium, chloride and carbon dioxide in the blood. Normal potassium levels range from 3.7 to 5.2 mEq/L (milliequivalents per liter), according to the National Institutes of Health. This test also helps doctors identify cases of reduced kidney function by revealing high levels of creatinine and blood urea nitrogen, waste products that normal kidneys filter out of the body.
Significance
Slightly elevated potassium levels may not cause any symptoms, but severe hyperkalemia causes fatigue, irregular heartbeat, tingling, weakness and numbness. Left untreated, high potassium levels lead to paralysis and death.
Prevention
Some people with chronic kidney disease follow a renal diet that restricts intake of sodium, potassium, protein and phosphorus. This helps the kidneys maintain normal levels of potassium and other substances in the blood. This type of diet limits the intake of high-potassium foods such as potatoes, bananas, oranges, dried peas, tomatoes and dairy products.
Patients replace these foods with lower-potassium alternatives, such as apples, green beans, non-dairy creamer, sorbet, onions and bell peppers. Doctors also use a process called hemodialysis to control potassium levels in patients who have end-stage renal disease. During this process, a machine filters the excess potassium out of the blood and returns the filtered blood to the body.
