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The body takes nutrients from food and converts them to energy. After the body has taken the food that it needs, waste products are left behind in the bowel and in the blood.
The kidneys and urinary system keep chemicals, such as potassium and sodium, and water in balance by removing a type of waste, called urea, from the blood. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys.
Two kidneys, a pair of purplish-brown organs, are located below the ribs toward the middle of the back. Their function is to:
remove liquid waste from the blood in the form of urine
keep a stable balance of salts and other substances in the blood
produce erythropoietin, a hormone that aids the formation of red blood cells
The kidneys remove urea from the blood through tiny filtering units called nephrons. There are about one million nephrons in each kidney, located in the medulla and the cortex. Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, and a small tube called a renal tubule.
Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney. Urine collects in the calyces and renal pelvis and moves into the ureter, where it flows down into the bladder.
In addition to filtering waste from the blood and assisting in the balance of fluids and other substances in the body, the kidneys perform other vital functions. These functions include:
Nephrology is the branch of medicine concerned with the diagnosis and treatment of conditions related to the kidneys, and physicians who specialize in kidney disease are called nephrologists. Other health professionals who treat kidney problems include primary care physicians, pediatricians, and urologists.
Problems with the kidneys may include conditions such as kidney failure, kidney stones, and kidney cancer. These problems with the kidneys may be caused by the following:
Diseases of the kidney and urinary tract remain a major cause of illness and death in the United States. The National Kidney Foundation states that more than 26 million Americans are affected by kidney and urologic diseases, and millions more are at risk.
The following are the most common symptoms of kidney disease. However, each individual may experience symptoms differently. Symptoms may include:
The symptoms of a kidney disease may resemble other conditions or medical problems. Always consult your physician for a diagnosis.