Polycystic kidney disease

Approximately 600,000 Americans have polycystic kidney disease (PKD), the number-four cause of kidney failure. PKD doesn’t discriminate; it equally affects different races and ethnic groups.

PKD is an inherited disorder that causes cysts filled with watery fluid or blood to form in or around the kidneys. Healthy kidneys are usually the size of an adult fist, but polycystic kidneys can be the size of a football and weigh up to 22 lbs. As these cysts grow, they can interfere with normal kidney function. About half of people with PKD are diagnosed with kidney failure and will require dialysis or a kidney transplant.

There are two types of PKD based on how the disorder is passed on from parent to child: autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD). An autosome is a chromosome that is not a sex chromosome. Normally people have 22 pairs of chromosomes which carry the genes with hereditary information. A hereditary or inherited disorder is caused by an abnormality in a gene or chromosome.

Autosomal dominant polycystic kidney disease (ADPKD) – The common form of the disease, ADPKD, accounts for nearly 90% of PKD cases. “Autosomal dominant” means that on a pair of autosomal chromosomes a person has one normal gene and one that is changed or mutant. The mutant gene is dominant and its hereditary information overrides the normal gene. Because children get one set of chromosomes from each parent, individuals with an autosomal dominant gene have a 50% chance of passing it to their children. Typically signs of the disease develop when a people reach their 30s.

Autosomal recessive polycystic kidney disease (ARPKD) –“Autosomal recessive” also means thata person has one normal gene and one that is mutant, but in this case the hereditary information of the healthy gene overrides the mutant one and the person is a carrier of the disease without any symptoms. If both parents are carriers, there is a 25% chance of their children inheriting both mutant genes and therefore exhibiting the disease.  Sometimes referred to as “infantile polycystic kidney disease,” ARPKD affects about 1 in 40,000 people in the United States. If kidney disease is already severe before the child is born, not enough amniotic fluid is generated which impacts the development of the fetus’s lungs. These babies may die soon after birth because of lung complications.

Symptoms of polycystic kidney disease

Common symptoms include:

  • High blood pressure
  • Headaches
  • Back or side pain related to enlarged kidneys
  • Increased abdominal size
  • Urinary tract infections
  • Blood in the urine
  • Kidney stones
  • Frequent urge to urinate
  • Progressive loss of kidney function

How is polycystic kidney disease diagnosed?

While certain blood and urine tests can detect kidney disease and declining kidney function, they can’t diagnose PKD. But several imaging studies can take a look at the kidneys themselves:

  • Ultrasonography uses ultrasound to create a picture of the kidneys on a computer screen. The physician is able to evaluate the size of the kidneys and see if cysts are present.
  • Computerized Tomography (CT) scan uses many X-ray images that a computer assimilates into cross-sectional views of the kidneys. It will show normal and abnormal areas within the organs.
  • Magnetic Resonance Image (MRI) uses a powerful magnetic field to construct an image of the kidneys.

Additionally, genetic testing can be performed if imaging test results are unclear, or to evaluate a potential living relative as a kidney donor for a family member in need.

How is polycystic kidney disease treated?

There is no cure for PKD but doctors can help patients manage symptoms and complications.

  • Blood pressure control may slow kidney damage. Treatment includes ACE inhibitors that prevent blood vessels from narrowing, a low-sodium, low-fat diet; exercise; stress reduction; and not smoking.
  • Acetaminophen (Tylenol®) is available over-the-counter and controls mild to moderate pain. In rare cases, if pain is severe, large cysts are drained surgically.
  • Antibiotics can treat urinary tract infections.
  • Increased fluid intake is recommended if blood in the urine occurs. Increased fluid dilutes the urine to help prevent the formation of blood clots within the urinary tract.
  • Liver function and cysts are observed and managed routinely.
  • Brain aneurysms are screened for and treated if they appear.
  • Chronic kidney disease (CKD) and its complications (including anemia, and bone and mineral metabolism disorder) are also treated.

Summary

PKD is a condition that affects nearly 600,000 Americans. Although there is no cure, treatment options are available. PKD comes in two different forms, and the more common one shows no signs of the disease until adulthood. People with a family history of PKD who plan to start a family should seek out a genetic counselor to help evaluate the risk of passing on the disease to their children. For more information, visit the PKD Foundation.

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