Autosomal Dominant PKD
What Is Autosomal Dominant PKD?
Autosomal dominant PKD 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 PKD 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 PKD live for decades without developing symptoms. For this reason, autosomal dominant PKD 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. High blood pressure occurs early in the disease, often before cysts appear.
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.
What Are the Symptoms of Autosomal Dominant PKD?
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 PKD 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 PKD Diagnosed?
To diagnose autosomal dominant PKD, a doctor typically observes three or more kidney cysts using ultrasound imaging. The diagnosis is strengthened by a family history of autosomal dominant PKD and the presence of cysts in other organs.
|An ultrasound imaging device passes
harmless sound waves through the body
to detect possible kidney systs.
In most cases of autosomal dominant PKD, 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 PKD.
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 methods such as computed tomography (CT scan) and magnetic resonance imaging (MRI) also can detect cysts, but these methods usually are not required because ultrasound provides adequate information. CT scans require x-rays and sometimes injected dyes.
In the future, DNA testing will be able to confirm a diagnosis of autosomal dominant PKD before cysts develop. (See The Search for PKD Genes)
How Is Autosomal Dominant PKD Treated?
Although a cure for autosomal dominant PKD 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 does not slow the disease's progression, in many cases, 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 PKD 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 PKD 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 PKD. 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 PKD patients do not develop cysts.