Section 11. Kidney and Urinary Tract Disorders

Chapter 146. Tubular and Cystic Kidney Disorders

Topics: Introduction | Renal Tubular Acidosis | Renal Glucosuria | Nephrogenic Diabetes Insipidus | Cystinuria | Fanconi's Syndrome | Hypophosphatemic Rickets | Hartnup Disease | Bartter's Syndrome | Liddle's Syndrome | Polycystic Kidney Disease | Medullary Cystic Disease | Medullary Sponge Kidney | Alport's Syndrome | Nail-Patella Syndrome

Polycystic Kidney Disease

Polycystic kidney disease is a hereditary disorder in which many fluid-filled sacs (cysts) form in both kidneys; the kidneys grow larger but have less functioning kidney tissue.

The genetic defect that causes polycystic kidney disease may be dominant or recessive. That is, a person with the disease has inherited either one copy of a dominant gene from one parent or two copies of a recessive gene, one from each parent. Those with dominant gene inheritance usually have no symptoms until adulthood; those with recessive gene inheritance develop severe illness in childhood.

See the figure Polycystic Kidney Disease.

The genetic defect leads to the widespread formation of cysts in the kidneys. Gradual enlargement of the cysts with increasing age is accompanied by a reduction of blood flow and scarring within the kidneys. Kidney stones may develop. Kidney failure can occur eventually. The genetic defect may also cause cysts to develop in other parts of the body, such as the liver and pancreas.

Symptoms and Complications

In the recessive form of this disease that begins during childhood, the cysts become very large and cause the abdomen to protrude. A severely affected newborn may die shortly after birth, because kidney failure can develop in the fetus, leading to poor development of the lungs. The liver is also affected, and at 5 to 10 years of age, a child with this disorder tends to develop high pressure in the blood vessels that connects the intestine and the liver (portal system). Eventually, liver failure and kidney failure occur.

In the dominant form of polycystic kidney disease, the cysts develop slowly in number and size. Typically, symptoms begin in early or middle adulthood, although occasionally the disease is not discovered until after death at autopsy. Symptoms usually include discomfort or pain in the abdomen or side (flank), blood in the urine, frequent urination, and intense crampy (colicky) pain from kidney stones. In other cases, fatigue, nausea, and other consequences of kidney failure may result because the person has less functioning kidney tissue. Chronic urinary tract infections can worsen the kidney failure. At least half of the people with polycystic kidney disease have high blood pressure at the time of diagnosis.

About one third of people who have polycystic kidney disease also have cysts in their liver, but these cysts do not affect liver function. As many as 10% of people have dilated blood vessels (aneurysms) in their brain. Usually, the dilated blood vessels cause headaches when they expand. Many of these brain aneurysms bleed and cause strokes.

Diagnosis, Prognosis, and Treatment

A doctor suspects this disease on the basis of family history and laboratory tests of kidney function. When the disease is advanced and the kidneys are very large, the diagnosis is obvious. Ultrasonography and computed tomography (CT) reveal the characteristic moth-eaten appearance of the kidneys and liver caused by the cysts.

Treating urinary tract infections and high blood pressure may prolong life. However, more than half of the people who have this disease develop kidney failure at some time in their life. Without dialysis or kidney transplantation, kidney failure is fatal.

Genetic testing is available to help people with polycystic kidney disease understand the probability that their children will inherit the condition.