Located at the rear of the abdominal cavity in the retroperitoneum, the kidneys receive blood from the paired renal arteries, and drain into the paired renal veins. Each kidney excretes urine into a ureter, itself a paired structure that empties into the urinary bladder.
Renal physiology is the study of kidney function, while nephrology is the medical specialty concerned with kidney diseases. Diseases of the kidney are diverse, but individuals with kidney disease frequently display characteristic clinical features. Common clinical conditions involving the kidney include the nephritic and nephrotic syndromes, renal cysts, acute kidney injury, chronic kidney disease, urinary tract infection, nephrolithiasis, and urinary tract obstruction.[1] Various cancers of the kidney exist; the most common adult renal cancer is renal cell carcinoma. Cancers, cysts, and some other renal conditions can be managed with removal of the kidney, or nephrectomy. When renal function, measured by glomerular filtration rate, is persistently poor, dialysis and kidney transplantation may be treatment options. Although they are not normally harmful, kidney stones can be painful, and repeated, chronic formation of stones can scar the kidneys. The removal of kidney stones involves ultrasound treatment to break up the stones into smaller pieces, which are then passed through the urinary tract. One common symptom of kidney stones is a sharp to disabling pain in the medial/lateral segments of the lower back or groin.
The kidneys remove wastes and extra
water from the blood to form urine. Urine flows from the kidneys to the bladder
through the ureters. The wastes in your blood come from the
normal breakdown of active muscle and from the food you eat. Your body uses the
food for energy and self-repair. After your body has taken what it needs from
the food, waste is sent to the blood. If your kidneys did not remove these
wastes, the wastes would build up in the blood and damage your body.
The actual filtering occurs in tiny units
inside your kidneys called nephrons. Every kidney has about a million nephrons.
In the nephron, tiny blood vessels called capillaries intertwine with tiny
urine-carrying tubes called tubules. A complicated chemical exchange takes
place, as waste materials and water leave your blood and enter your urinary
system.
At first, the tubules receive a combination
of waste materials and chemicals that your body can still use. Your kidneys
measure out chemicals like sodium, phosphorus, and potassium and release them
back to the blood to return to the body. In this way, your kidneys regulate the
body's level of these substances. The right balance is necessary for life, but
excess levels can be harmful.