Polycystic Kidney Disease

Polycystic kidney disease is a genetic disorder that causes numerous cysts to grow in the kidneys. A kidney cyst is an abnormal sac filled with fluid. PKD cysts can greatly enlarge the kidneys while replacing much of their normal structure, resulting in chronic kidney disease (CKD), which causes reduced kidney function over time. CKD may lead to kidney failure, described as end-stage kidney disease or ESRD when treated with a kidney transplant or blood-filtering treatments called dialysis.

PKD cysts are different from the usually harmless “simple” cysts that often form in the kidneys later in life. PKD cysts are more numerous and cause complications, such as high blood pressure, cysts in the liver, and problems with blood vessels in the brain and heart.

Polycystic kidney disease (PKD) runs in families. In PKD, the cysts take the place of the normal tissue. They enlarge the kidneys and make them work poorly, leading to kidney failure. When PKD causes kidneys to fail – which usually happens after many years – people need dialysis or kidney transplantation. About half of people with the most common type of PKD end up with kidney failure. PKD also causes cysts in other parts of the body, such as the liver.

Symptoms of PKD include

• Pain in the back and lower sides
• Headaches
• Urinary tract infections
• Blood in the urine

Doctors diagnose PKD with imaging tests and family history. Treatments include medications, and, when people with PKD develop kidney failure, dialysis or kidney transplants.

Prevention

Scientists have not yet found a way to prevent PKD. However, people with PKD may slow the progression of kidney damage caused by high blood pressure through lifestyle changes, diet, and blood pressure medications. People with PKD should be physically active 30 minutes a day most days of the week. If lifestyle and diet changes do not control a person’s blood pressure, a health care provider may prescribe one or more blood pressure medications, including ACE inhibitors or ARBs.

Risk Factors

Estimates of PKD’s prevalence range from one in 400 to one in 1,000 people.1 According to the United States Renal Data System, PKD accounts for 2.2 percent of new cases of kidney failure each year in the United States. Annually, eight people per 1 million have kidney failure as a result of PKD.2

Polycystic kidney disease exists around the world and in all races. The disorder occurs equally in women and men, although men are more likely to develop kidney failure from PKD. Women with PKD and high blood pressure who have had more than three pregnancies also have an increased chance of developing kidney failure.

Causes

A gene mutation, or defect, causes polycystic kidney disease. Genes provide instructions for making proteins in the body. A gene mutation is a permanent change in the deoxyribonucleic acid (DNA) sequence that makes up a gene. In most cases of PKD, a person inherits the gene mutation, meaning a parent passes it on in his or her genes. Researchers have found three different gene mutations associated with PKD.

Symptoms

In many cases, PKD does not cause signs or symptoms until cysts are half an inch or larger. When present, the most common symptoms are pain in the back and sides—between the ribs and hips—and headaches. The pain can be temporary or persistent, mild or severe. Hematuria—blood in the urine—may also be a sign of autosomal dominant PKD.

Diagnosis

Health care providers diagnose autosomal dominant PKD using imaging tests and genetic testing.

Imaging Tests

A radiologist—a doctor who specializes in medical imaging—will interpret the images produced by the following imaging tests:

• An abdominal ultrasound can create images of the entire urinary tract or focus specifically on the kidneys. The images can show cysts in the kidneys.
• CT scans use a combination of x-rays and computer technology to create images. CT scans can show more precise images of cysts in the kidneys.
• Magnetic resonance imaging (MRI) machines use radio waves and magnets to produce detailed pictures of the body’s internal organs and soft tissues without using x-rays. A health care provider can use MRIs to measure kidney and cyst volume and monitor kidney and cyst growth, which can help track progression of the disorder.

Kidney imaging findings vary widely, depending on a person’s age. Younger people usually have fewer and smaller cysts. Health care providers have therefore developed specific criteria for diagnosing the disorder with kidney imaging findings, depending on age. For example, the presence of at least two cysts in each kidney by age 30 in a person with a family history of the disorder can confirm the diagnosis of autosomal dominant PKD. A family history of autosomal dominant PKD and cysts found in other organs make the diagnosis more likely.

Genetic Testing

The health care provider may refer a person suspected of having autosomal dominant PKD to a geneticist—a doctor who specializes in genetic disorders.

Genetic testing can show whether a person’s cells carry a gene mutation that causes autosomal dominant PKD. A health care provider may also use genetic testing results to determine whether someone with a family history of PKD is likely to develop the disorder in the future. Prenatal testing can diagnose autosomal recessive PKD in unborn children.

Two factors limit the usefulness of genetic testing for PKD:

Detection of a mutated gene cannot predict the onset of symptoms or how serious the disorder will be. Even if a health care provider finds a mutated gene, no specific cure for the disorder exists.

Treatment

Although a cure for autosomal dominant PKD is not currently available, treatment can ease symptoms and prolong life.

Treatments for the symptoms and complications of autosomal dominant PKD include the following:

• Pain. A health care provider will first determine what is causing the pain and then recommend treatment. If cyst growth is causing persistent pain, the health care provider may first suggest over-the-counter pain medications such as aspirin or acetaminophen. People should consult their health care provider before taking any over-thecounter medication because some may be harmful to the kidneys. For most cases of severe pain due to cyst growth, surgery to shrink cysts can temporarily relieve pain in the back and sides. However, surgery does not slow the disorder’s progression toward kidney failure.
• 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. Health care providers have found these medications to protect the kidneys in people with other forms of kidney disease besides autosomal dominant PKD. Sometimes a patient can control blood pressure through diet and exercise alone.
• Kidney failure. After many years, PKD can cause the kidneys to fail. Kidneys are essential for life, so people with kidney failure must receive either dialysis or a kidney transplant to replace kidney function.  A kidney transplant is surgery to place a healthy kidney from a person who has just died or a living person, most often a family member, into the patient’s body. People with autosomal dominant PKD have no more complications after transplantation than people with kidney failure from other causes.
• UTIs. People with autosomal dominant PKD tend to have frequent UTIs, which health care providers treat with antibiotics. People with the disorder should seek treatment for a UTI immediately because infection can spread through the urinary tract to the kidney cysts. Cyst infections are difficult to treat because many antibiotics do not reach the cysts.
• Kidney stones. Treatment of kidney stones in people with autosomal dominant PKD is similar to treatment in people without the disorder. Breaking up stones with shock waves and removing stones through a small incision do not cause more complications in people with autosomal dominant PKD than in people without the disorder.
• Liver cysts. Most people with liver cysts do not need treatment. A health care provider may aspirate—drain with a needle through the skin—liver cysts in people who have symptoms. In the most severe cases, a patient may need a liver transplant. Infections in liver cysts can be treated with antibiotics and aspiration.
• Pancreatitis. Treatment for pancreatitis usually involves a hospital stay with intravenous (IV) fluids and antibiotics.
• Abnormal heart valves. Abnormal heart valves in people with autosomal dominant PKD rarely require valve replacement. A patient may need further tests if a health care provider detects a heart murmur—a blowing, whooshing, or rasping sound heard with a stethoscope during a heartbeat.
• Diverticula. A high-fiber diet and pain medications help relieve symptoms when diverticula are present. Uncomplicated infection of the diverticula with mild symptoms usually requires the person to rest, take oral antibiotics, and be on a liquid diet for a period of time.
• Brain aneurysms. People with autosomal dominant PKD should see a health care provider if they have severe or recurring headaches—even before considering over-the-counter pain medications. Small aneurysms rarely require surgery. A person with a brain aneurysm should avoid smoking and control blood pressure and lipids—fats in the blood.