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. The two main types of PKD are autosomal dominant PKD and autosomal recessive PKD.
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.
What causes polycystic kidney disease?
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. The remaining cases, the gene mutation develops spontaneously. In spontaneous cases, neither parent carries a copy of the mutated gene.
Researchers have found three different gene mutations associated with PKD. Two of the genes are associated with autosomal dominant PKD. The third gene is associated with autosomal recessive PKD. Gene mutations that cause PKD to affect proteins that play a role in kidney development.
How common is polycystic kidney disease and who is more likely to have the disease?
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.
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.
What is autosomal dominant polycystic kidney disease?
Autosomal dominant PKD is the most common form of PKD and the most common inherited disorder of the kidneys. The term autosomal dominant means a child can get the disorder by inheriting the gene mutation from only one parent. Each child of a parent with an autosomal dominant mutation has a 50 percent chance of inheriting the mutated gene. About 10 percent of autosomal dominant PKD cases occur spontaneously.
Health care providers identify most cases of autosomal dominant PKD between the ages of 30 and 50. For this reason, health care providers often call autosomal dominant PKD “adult PKD.” However, the onset of kidney damage and how quickly the disorder progresses varies. In some cases, cysts may form earlier in life and grow quickly, causing symptoms in childhood.
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 roughly retaining their kidney shape. In fully developed autosomal dominant PKD, a cyst-filled kidney can weigh as much as 20 to 30 pounds.
What are the signs and symptoms of autosomal dominant polycystic kidney disease?
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 a 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.
What are the complications of autosomal dominant polycystic kidney disease?
The complications of autosomal dominant PKD include the following:
Cyst infection, other types of urinary tract infections (UTIs), bleeding into cysts, kidney stones, or stretching of the fibrous tissue around the kidney because of cyst growth can cause pain in the area of the kidneys.
High blood pressure
High blood pressure is present in about half of the people with autosomal dominant PKD and normal kidney function between the ages of 20 and 35.4 Almost 100 percent of people with kidney failure and autosomal dominant PKD have high blood pressure.1 High blood pressure— greater than 140/90 mm Hg—increases the likelihood of heart disease and stroke, as well as adding to the damage already done to the kidneys by the cysts.
Kidney failure means the kidneys no longer work well enough to maintain health. A person with kidney failure may have the following symptoms:
- little or no urination
- edema—swelling, usually in the legs, feet, or ankles and less often in the hands or face
- fatigue, or feeling tired
- generalized itching or numbness
- dry skin
- weight loss
- appetite loss
- sleep problems
- trouble concentrating
- darkened skin
- muscle cramps
- shortness of breath
- chest pain
Untreated kidney failure can lead to coma and death. More than half of people with autosomal dominant PKD progress to kidney failure by age 70.
Kidney cysts block the flow of urine through the kidneys. Stagnant urine can set the stage for infection. Bacteria enter the urinary tract through the urethra and spread up to the Sometimes, the kidney cysts become infected. UTIs may cause scarring in the kidneys.
About 20 percent of people with autosomal dominant PKD have kidney stones.1 Kidney stones can block the flow of urine and cause pain.
Liver cysts are the most common non-kidney complication of autosomal dominant PKD. They generally cause no symptoms.
PKD can also cause cysts in the pancreas. Pancreatic cysts rarely cause pancreatitis— inflammation, or swelling, of the pancreas.
Abnormal heart valves
Abnormal heart valves may occur in up to 25 percent of people with autosomal dominant PKD. Insufficient blood flow in the aorta—the large artery that carries blood from the heart—may result from the abnormal heart valves.
Diverticula are small pouches or sacs, that push outward through weak spots in the colon wall. This complication is more common in people with PKD who have kidney failure.
An aneurysm is a bulge in the wall of a blood Aneurysms in the brain might cause headaches that are severe or feel different from other headaches. Brain aneurysms can rupture, or break open, causing bleeding inside the skull. A ruptured aneurysm in the brain is a life-threatening condition and requires immediate medical attention.
How do health care providers diagnose autosomal dominant polycystic kidney disease?
Health care providers diagnose autosomal dominant PKD using imaging tests and genetic testing.
A radiologist—a doctor who specializes in medical imaging—will interpret the images produced by the following imaging tests:
It uses a device, called a transducer, that bounces safe, painless sound waves off organs to create an image of their An abdominal ultrasound can create images of the entire urinary tract or focus specifically on the kidneys. A specially trained technician performs the procedure in a health care provider’s office, an outpatient center, or a hospital. A patient does not need anesthesia. The images can show cysts in the kidneys.
They use a combination of x-rays and computer technology to create a CT scan, a health care provider may give the patient an injection of a special dye, called contrast medium. CT scans require the patient to lie on a table that slides into a donut-shaped device where the x-rays are taken. An x-ray technician performs the procedure in an outpatient center or a hospital. Adults do not need anesthesia. A health care provider may give infants and children a sedative to help them fall asleep for the test. CT scans can show more precise images of cysts in the kidneys.
Magnetic resonance imaging (MRI)
These machines use radio waves and magnets to produce detailed pictures of the body’s internal organs and soft tissues without using x-rays. An MRI may include the injection of a contrast medium. With most MRI machines, the patient lies on a table that slides into a tunnel-shaped device that is often open-ended or closed at one end; some machines allow the patient to lie in a more open space. A specially trained technician performs the procedure in an outpatient center or a hospital. A patient does not need anesthesia, though a health care provider may use light sedation for people with a fear of confined spaces. A health care provider can use MRIs to measure kidney and cyst volume and monitor kidney and cyst growth, which can help track the progression of the disorder.
The health care provider may refer a person suspected of having autosomal dominant PKD to a geneticist—a doctor who specializes in genetic disorders. For a genetic test, the geneticist takes a blood or saliva sample and analyzes the DNA for gene mutations that cause autosomal dominant PKD, called PKD1 and PKD2, or autosomal recessive PKD, called PKHD1. Personnel in specialized labs generally perform all genetic testing. A patient may not receive the results for several months because of the complexity of the testing.
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
- Even if a health care provider finds a mutated gene, no specific cure for the disorder
How do health care providers treat autosomal dominant polycystic kidney disease?
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:
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-the counter 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. Some health care providers recommend blood pressure medications called angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs). 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.
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. The two forms of dialysis are hemodialysis and peritoneal Hemodialysis uses a machine to circulate a patient’s blood through a filter outside the body. Peritoneal dialysis uses the lining of the abdomen to filter the blood inside the body.
A kidney transplant is a 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.
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 the 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.
Treatment of kidney stones in people with autosomal dominant PKD is similar to treatment in people without the disorder. Potassium citrate, taken by mouth, is useful for treating the types of kidney stones associated with autosomal dominant PKD.
Breaking up stones with shock waves and removing stones through a small incision does not cause more complications in people with autosomal dominant PKD than in people without the disorder.
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.
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.
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. Sometimes an infection is serious enough to require a hospital stay, IV antibiotics, and possibly surgery.
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.
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