Polycystic kidney disease
Polycystic kidney disease (PKD) is a genetic disorder that can lead to severe symptoms and complications. Two types of polycystic kidney disease are autosomal recessive polycystic kidney disease and autosomal dominant polycystic kidney disease.
Definition & Facts
Polycystic kidney disease is characterized by the presence of cysts that develop on the kidneys. The cysts are round sacs of tissue containing fluid. The sizes vary but often accumulate more fluid as they grow and enlarge. Cysts may also appear in the liver and other bodily organs.
There is a 50 percent chance of inheriting autosomal dominant polycystic kidney disease if one parent has the disease. 90 percent of PKD cases result from this type of PKD. There is a 25 percent chance of inheriting autosomal recessive polycystic kidney disease if both parents carry the genetic mutation. PKD affects nearly 600,000 people per year, according to the National Kidney Foundation.
Symptoms & Complaints
High blood pressure in children should be investigated for the presence of polycystic kidney disease. Adults may have conditions associated with PKD such as blindness, liver disease, heart valve prolapse, and diverticula or pockets in the wall of the colon. A decline in kidney function accompanies these symptoms. People often seek help when they discover blood in their urine because the cysts break and bleed.
PKD is usually passed down through genetic traits. Rarely, PKD may also arise out of spontaneous genetic mutations that are not inherited. The affected genes provide instructions for protein formation, giving chemical signals to the kidney cell nucleus. If this process is disrupted by mutations in gene function, thousands of cysts form on the kidneys, hampering renal function.
If one parent has the autosomal dominant PKD gene, the child has a 50 percent chance of developing the disease. Many people may carry the gene and pass it to their offspring without knowing it. Only one copy of the abnormal gene is needed to pass on autosomal dominant PKD. Autosomal dominant PKD occurs in children, but adults are more commonly affected between the ages of 30 and 40. It affects approximately 400,000 people in the United States.
While there is always a family history associated with autosomal dominant PKD, there is usually not a family history associated with autosomal recessive PKD because there needs to be a genetic mutation in both parents' genes in order for the disease to occur in their child, and each parent only has one genetic mutation. 1 in 20,000 children worldwide have autosomal recessive PKD.
Diagnosis & Tests
Doctors will test for hypertension. Sometimes masses in the flanks can be felt by the physician if the disease has advanced. If kidney disease is suspected, tests will be ordered to determine the amount of healthy kidney tissue and evaluate the size and number of cysts present.
An ultrasound exam emits sound waves that return to a transducer. A computer is used to create images of the kidneys from the sound waves. Cross section images of the kidney can be accessed through a CT scan. An alternative to a CT scan is an MRI, where magnetic fields and radio waves generate the images. Routine laboratory tests will be ordered, including a complete blood count and uric acid levels.
After PKD is diagnosed, renal failure is staged by glomerular filtration rate or GFR. Glomerular filtration means the ability of the kidneys to filter waste from the blood. A glomerular filtration rate of less than 60 mL/minute indicates complete kidney failure. A GFR of 60-80 mL/minute does not indicate chronic kidney disease unless other tests ordered indicate the disease.
Treatment & Therapy
The goal of treatment is to improve the quality of life of the patient and to improve his or her renal function. Blood pressure must be controlled, and urinary tract infections treated. Hematuria, or blood in the urine due to cysts breaking must be addressed, and abdominal pain due to enlarged kidneys managed.
As the disease progresses, surgery will be offered to excise large cysts and make the person more comfortable. After years of chronic disease, healthy kidney tissue is completely replaced by cellular sacs of fluid. As they rupture, they cause severe pain. At this point, the disease ceases to be manageable, one or both kidneys may need to be removed, and dialysis will become a factor.
The University of Maryland Division of Transplantation is one of a few hospitals in the country that treat both diseased kidneys by removal and replacement with one healthy kidney during the same operation.
Prevention & Prophylaxis