What is autosomal dominant polycystic kidney disease?
Autosomal dominant polycystic kidney disease is one of the most common inherited disorders. The phrase "autosomal dominant" means that if one parent has the disease, there is a 50-percent chance that the disease will pass to a child (see Genetic Diseases). At least one parent must have the disease for a child to inherit it. Either the mother or father can pass it along, but new mutations may account for one-fourth of new cases. In some rare cases, the cause of autosomal dominant polycystic kidney disease occurs spontaneously in the child soon after conception—in these cases the parents are not the source of this disease.
Many people with autosomal dominant polycystic kidney disease live for decades without developing symptoms. For this reason, autosomal dominant polycystic kidney disease is often called "adult polycystic kidney disease." Yet, in some cases, cysts may form earlier, even in the first years of life.
The disease is thought to occur equally in men and women and equally in people of all races. However, some studies suggest that it occurs more often in whites than in blacks and more often in females than in males.
The cysts grow out of nephrons, the tiny filtering units inside the kidneys. The cysts eventually separate from the nephrons and continue to enlarge. The kidneys enlarge along with the cysts (which can number in the thousands), while retaining roughly their kidney shape. In fully developed PKD, a cyst-filled kidney can weigh as much as 22 pounds. High blood pressure occurs early in the disease, often before cysts appear.
What are the symptoms of autosomal dominant polycystic kidney disease?
The most common symptoms are pain in the back and the sides (between the ribs and hips), and headaches. The dull pain can be temporary or persistent, mild or severe.
People with autosomal dominant polycystic kidney disease also can experience the following:
- urinary tract infections
- hematuria (blood in the urine)
- liver and pancreatic cysts
- abnormal heart valves
- high blood pressure
- kidney stones
- aneurysms (bulges in the walls of blood vessels) in the brain
- diverticulosis (small sacs on the colon)
How is autosomal dominant polycystic kidney disease diagnosed?
To diagnose autosomal dominant polycystic kidney disease, a doctor typically observes three or more kidney cysts using ultrasound imaging. The diagnosis is strengthened by a family history of autosomal dominant polycystic kidney disease and the presence of cysts in other organs.
 | | An ultrasound imaging device passes harmless sound waves through the body to detect possible kidney cysts. | |
In most cases of autosomal dominant polycystic kidney disease, the person's physical condition appears normal for many years, even decades, so the disease can go unnoticed. Physical checkups and blood and urine tests may not lead to diagnosis. The slow, undetected progression is why some people live for many years without knowing they have autosomal dominant polycystic kidney disease.
Once cysts have formed, however, diagnosis is possible with imaging technology. Ultrasound, which passes sound waves through the body to create a picture of the kidneys, is used most often. Ultrasound imaging employs no injected dyes or radiation and is safe for all patients, including pregnant women. It can also detect cysts in the kidneys of a fetus.
More powerful and expensive imaging procedures such as computed tomography (CT scan) and magnetic resonance imaging (MRI) also can detect cysts, but they usually are not required for diagnosis because ultrasound provides adequate information. CT scans require x rays and sometimes injected dyes.
A genetic test can detect mutations in the PKD1 and PKD2 genes. Although this test can detect the presence of the autosomal dominant polycystic kidney disease mutations before cysts develop, its usefulness is limited by two factors; it cannot predict the onset or ultimate severity of the disease, and no absolute cure is available to prevent the onset of the disease. On the other hand, a young person who knows of a polycystic kidney disease gene mutation may be able to forestall the disease through diet and blood pressure control. The test may also be used to determine whether a young member of a polycystic kidney disease family can safely donate a kidney to a parent. Anyone considering genetic testing should receive counseling to understand all the implications of the test.
How is autosomal dominant polycystic kidney disease treated?
Although a cure for autosomal dominant polycystic kidney disease is not available, treatment can ease the symptoms and prolong life.
Pain. A doctor will first suggest over-the-counter pain medications, such as aspirin or Tylenol. For most but not all cases of severe pain, surgery to shrink cysts can relieve pain in the back and flanks. However, surgery provides only temporary relief and usually does not slow the disease's progression toward kidney failure.
Headaches that are severe or that seem to feel different from other headaches might be caused by aneurysms, or swollen blood vessels, in the brain. Headaches also can be caused by high blood pressure. People with autosomal dominant polycystic kidney disease should see a doctor if they have severe or recurring headaches—even before considering over-the-counter pain medications.
Urinary tract infections. Patients with autosomal dominant polycystic kidney disease tend to have frequent urinary tract infections, which can be treated with antibiotics. People with the disease should seek treatment for urinary tract infections immediately, because infection can spread from the urinary tract to the cysts in the kidneys. Cyst infections are difficult to treat because many antibiotics do not penetrate into the cysts. However, some antibiotics are effective.
High blood pressure. Keeping blood pressure under control can slow the effects of autosomal dominant polycystic kidney disease. Lifestyle changes and various medications can lower high blood pressure. Patients should ask their doctors about such treatments. Sometimes proper diet and exercise are enough to keep blood pressure low.
End-stage renal disease. Because kidneys are essential for life, people with ESRD must seek one of two options for replacing kidney functions: dialysis or transplantation. In hemodialysis, blood is circulated into an external machine, where it is cleaned before reentering the body; in peritoneal dialysis, a fluid is introduced into the abdomen, where it absorbs wastes, and it is then removed. Transplantation of healthy kidneys into ESRD patients has become a common and successful procedure. Healthy (non-PKD) kidneys transplanted into polycystic kidney disease patients do not develop cysts.
source: http://kidney.niddk.nih.gov/kudiseases/pubs/polycystic/index.htm
