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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 tissue.
There are several genetic defects that causes polycystic kidney disease. Several types are caused by dominant genes, and one rare type is caused by a recessive gene. 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.
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Polycystic Kidney Disease
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In polycystic kidney disease, many cysts form in both kidneys. The cysts gradually enlarge, destroying some or most of the normal tissue in the kidneys.
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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 rare, 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 connect the intestine and the liver (portal system). Eventually, liver failure and kidney failure occur.
In the more common, dominant form of polycystic kidney disease, the cysts develop slowly in number and size. Typically, symptoms begin in early or middle adulthood. Sometimes symptoms are so mild that people with the disease will live their whole life without ever having known that they had the disorder. 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 slowly developing kidney failure may result because the person has less functioning kidney tissue. Repeated urinary tract infections can worsen the kidney failure. At least half of the people with polycystic kidney disease have high blood pressure by the time the disorder is recognized.
About one third of people who have the dominant form of 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. Ultrasonography and computed tomography (CT) reveal the characteristic appearance of cysts in the kidneys and liver.
Effective treatment of urinary tract infections and high blood pressure slows the rate of kidney destruction. 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.
Last full review/revision December 2006 by Peter C. Brazy, MD
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