Polycystic Kidney Disease

Polycystic kidney disease (PKD) is an inherited disorder that causes many fluid-filled sacs, called cysts, to form in both kidneys. The cysts cause problems because they interfere with the function of the kidney and damage the kidney tissues. The cysts can grow very big (the size of a grapefruit, for example) and/or there can be hundreds, even thousands, of cysts. Over the years, the cysts can cause the kidneys to stop working (kidney failure).

PKD can also cause cysts to form in the liver, the heart, or blood vessels in the brain.

Two types of PKD
There are two types of inherited PKD.

• Autosomal dominant PKD (ADPKD) is the most common, and accounts for about 90% of all cases. Symptoms usually begin between the ages of 30 and 40, but can start earlier. If a parent has the disorder, there is a 50% chance that his/her child will have the disorder.
• Autosomal recessive PKD (ARPKD) is rare, and occurs in young children. It may begin before the child is born, at birth, as an infant, or in early childhood. Both parents must pass this disorder on to their child for the child to develop it.

There is also another type of disorder called acquired cystic kidney disease (ACKD). This is not inherited, but instead develops in people who have long-term kidney problems.

Symptoms
People with autosomal dominant PKD usually have:

• Pain in the back and sides between the ribs and hips. The pain may come and go or be constant, and may be mild or severe
• Headaches

They may also have:

• Urinary tract infections
• Blood in the urine (hematuria)
• Cysts in other organs of the body, usually the liver
• High blood pressure
• Kidney stones

Children with autosomal recessive PKD may have:

• High blood pressure
• Urinary tract infections
• Frequent urination
• Cysts in other organs of the body, usually the liver

Diagnosis
Taking a look at the kidneys with ultrasound will detect the cysts in the kidneys. Finding cysts in the liver or other organs can confirm the diagnosis.

Treatment
There is no cure for either inherited form of PKD. Treatment is available to relieve the symptoms, and may include:

• Pain medications
• Antibiotics for urinary tract infections
• Medicines, diet, and exercise to control high blood pressure

If one or both kidneys shut down or can no longer meet the body's needs, there are two options: dialysis, which does the functions of the kidneys instead, or transplantation, which replaces the failed kidney. A healthy kidney transplanted into a person with PKD does not develop cysts.

Future research
In 1994, researchers identified a gene on Chromosome 16 that was associated with many cases of ADPKD. In 2002, researchers identified a gene on Chromosome 6 associated with ARPKD. It is not yet known what the exact role is of these genes in PKD, or why the cysts form in the body. Further research will focus on how the genes cause the disorder, and how it can be best treated, with the eventual goal of eliminating PKD altogether.

Sources:
- "Polycystic Kidney Disease." Kidney & Urologic Diseases. National Kidney and Urologic Diseases Information Clearinghouse. 25 Nov 2006 <http://kidney.niddk.nih.gov/kudiseases/pubs/polycystic/index.htm>.
- "About PKD." PKD Foundation. 25 Nov 2006 <http://www.pkdcure.org/site/PageServer?pagename=pkdabt_aboutPkd>.