Polycystic kidney disease is an inherited kidney disorder that enlarges the kidneys and interferes with their function because of multiple cysts on the kidneys.

PKD is almost always inherited. In about 10 of every 100 cases, the disease is caused by a defective gene that is not inherited.

Causes of Polycystic kidney disease

Polycystic kidney disease (PKD) is an inherited disorder (with autosomal dominant inheritance -- if one parent carries the gene, the children have a 50% chance of developing the disorder) where multiple clusters of cysts form on the kidneys. The exact mechanism that triggers cyst formation is unknown.

Cysts in the kidneys are associated with aneurysms of the blood vessels in the brain. They may be associated with diverticula of the colon, and with cysts in the liver, pancreas, and testes. As many as 50% of people with polycystic kidney disease also have cysts on the liver.

In early stages of Polycystic kidney disease, the cysts enlarge the kidney and interfere with kidney function, resulting in chronic high blood pressure and kidney infections. The cysts may cause the kidneys to increase production of erythropoietin (the hormone that stimulates production of red blood cells) resulting in increased number of red blood cells, rather than the expected anemia. Bleeding into a cyst can cause flank pain. Kidney stones are more common than in people without the disorder. Hypertension caused by polycystic kidneys may be difficult to control.

Polycystic kidney disease is slowly progressive, eventually resulting in end-stage kidney failure. It is also associated with liver disease, including infection of liver cysts. An autosomal recessive form of polycystic kidney disease also exists and appears in infancy or childhood; it tends to be very serious and progresses rapidly, resulting in end-stage kidney failure and generally causing death in infancy or childhood.

Autosomal dominant Polycystic kidney disease occurs in both children and adults, but it is much more common in adults, often not presenting symptoms until middle age. It affects nearly 1 in 1,000 Americans. The actual number may be more, as some people do not have symptoms. The disorder may not be discovered unless procedures showing the disease are performed for other reasons.

Risks include a personal or family history of polycystic kidney disease.

Diagnosis of Polycystic kidney disease

Many patients who have PKD don't have any symptoms. Their condition may not be discovered unless tests that detect it are performed for other reasons.

When symptoms of PKD are present, the diagnostic procedure begins with a family medical history and physical examination of the patient. If several family members have PKD, there is a strong likelihood that the patient has it too. If the disease is advanced, the doctor will be able to feel the patient's enlarged kidneys. Heart murmur, high blood pressure, and other signs of cardiac impairment can also be detected.

Urinalysis and creatine clearance tests can indicate how effectively the kidneys are functioning. Scanning procedures using intravenous dye reveal kidney enlargement or deformity and scarring caused by cysts. Ultrasound and computed tomography scans (CT) can reveal kidney enlargement and the cysts that caused it. CT scans can highlight cyst-damaged areas of the kidneys.

Treatment of Polycystic kidney disease

There is no way to prevent cysts from forming or becoming enlarged, or to prevent PKD from progressing to kidney failure. Treatment goals include:

• Preserving healthy kidney tissue
• Controlling symptoms
• Preventing infection and other complications.

If adult PKD is diagnosed before symptoms become evident, urinalysis and other diagnostic tests are performed at six-week intervals to monitor the patient's health status. If results indicate the presence of infection or another PKD-related health problem:

• Aggressive antibiotic therapy is initiated to prevent inflammation that can accelerate disease progression.
• Iron supplements or infusion of red blood cells are used to treat anemia.
• Surgery may be needed to drain cysts that bleed, cause pain, have become infected, or interfere with normal kidney function.

Lowering high blood pressure can slow loss of kidney function. Blood-pressure control, which is the cornerstone of PKD treatment, is difficult to achieve. Therapy may include:

• Antihypertensives
• Diuretic medications
• Low-salt diet.

As kidney function declines, some patients need dialysis or a kidney transplant. Some patients need both types of treatment.