Kidneys Health Article

KEY TERMS

Adrenal gland—Small gland on top of each kidney that produces and releases several different hormones that are involved in maintaining internal fluid and salt levels and also mediates stress responses.

Angiotensin I—Inactive form of angiotensin that circulates in the blood; it is a precursor of angiotensin II.

Angiotensin II—Active form of angiotensin that constricts blood vessels, thus raising blood pressure.

Capillary—Small blood vessel that is the point of connection for blood and veins and where exchanges occur between the blood and tissue.

Hydronephrosis—Distention of the renal pelvis that occurs when urine is trapped in the kidney and blocked from flowing into the bladder.

Ureter—Carries urine from the kidney to the bladder.

increase in water volume in the blood increases blood pressure. Many medications for high blood pressure act by working on the kidneys to decrease blood volume and therefore blood pressure. These blood pressure medications are collectively known as diuretics.

Role in human health

The kidneys play a crucial role in human health because they perform many vital functions. The kidneys work constantly, simultaneously, and influence each other. Individuals are born with two kidneys but can function with one. However, a person with kidney function at 10–15% of capacity will require dialysis or a kidney transplant to sustain life. Individuals with high blood pressure and diabetes have a significant risk of kidney disease.

Diabetic nephropathy

Diabetic patients cannot process blood glucose properly, and if their disease is untreated or poorly controlled, it can lead to high blood sugar levels. This can damage the nephrons, leading to diabetic neuropathy. This usually means that soft kidney tissue hardens and thickens, a process called sclerosis; this is especially true for the glomerulus. The American Diabetes Association estimates that 35–45% of type 1 diabetics and 20–30% of type 2 diabetics have damaged kidneys. Because the symptoms of nephropathy may not appear until 80% of kidney function is gone, periodic tests of kidney function and strict compliance with diet and treatment regimens are important for patients with diabetes.

High blood pressure

The kidneys use small blood vessels called capillaries to filter blood and to help create a pressure gradient to move fluid through the nephron. Continuous high blood pressure can damage the fragile walls of these vessels. When this happens, blood may not filter properly, allowing waste products and/or drug levels to build up, some times to dangerous or fatal levels. Kidney stones Kidneys stones occur when crystals form in the lumen of the tubules or in the ureters. The stones are most commonly made of calcium and oxalate or phosphate. The basis of stone formation is not clear but certain foods in certain people can cause them to accrete. Kidney stones can be extremely painful, and can also cause hydronephrosis. Patients with kidney stones are encour aged to drink plenty of water in effort to have the stone excreted in the urine. In some cases, kidney stones must be surgically removed.

Polycystic kidney disease

Polycystic kidney disease (PKD) is an inherited disease in which cysts form in the kidney. These fluid-filled cysts can take over a significant amount of space in the kidney, eventually reducing kidney function and causing kidney failure. Most cases of PKD show no symptoms until the patient is well into adulthood. PKD that appears in children is often more virulent, frequently leading to kidney failure and death. Nutrition and dietary modification play a major role in controlling the progression of PKD.

Wilms' tumor

Wilms' tumor, or nephroblastoma, is a cancer of the kidney that appears during childhood. Both sporadic cases and a few rare inherited cases have been linked to mutations in the Wilm's tumor gene (WT1) on chrom-some 11. Many cases of Wilms' tumor are curable if caught early enough.

BOOKS

Cohen, Barbara, and Dena Wood. Structure and Function of the Human Body, 7th ed. Philadelphia, PA: Lippincott Williams and Wilkins, 2000.

Johnson, R.J., and J. Feehally. Comprehensive Clinical Nephrology. London: Harcourt Publishers, 2000.

ORGANIZATIONS

National Kidney Foundation. 30 East 33rd St. Suite 1100, New York, NY 10016. (800) 622-9010. <http://www.kidney.org>.

Polycystic Kidney Disease Foundation. 4901 Main St. Suite 200, Kansas City, MO 64112. (800) PKD-CURE. <http://www.pkdcure.org>.

Susan M. Mockus, Ph.D.