http://www.pkdcure.org/aboutPkd1.htm#whatisWhat is PKD?
Polycystic Kidney Disease comes in two hereditary forms:
Autosomal dominant (ADPKD), the most common of all life-threatening genetic diseases.
Autosomal recessive (ARPKD), a relatively rare disease that often causes significant mortality in the first month of life.
A normal kidney is the size of a human fist. However, with the presence of PKD, cysts develop in both kidneys. There may be just a few cysts or many, and the cysts may range in size from a pinhead to the size of a grapefruit. When many cysts develop, the kidneys can grow to be the size of a football or larger and weigh as much as 38 pounds each.
What are cysts?
A cyst in the kidney begins as an outpouching of the nephron, similar to a blister. Cysts can occur anywhere on the length of the nephron. Although polycystic means many cysts, not every nephron forms cysts. The fluid inside the cysts often reflects the area in the nephron from which the cyst arose.
Approximately 70 percent of cysts detach from the nephron when they are still very small, about 2 mm (1/8 inch) in diameter. Over time the cysts enlarge and can become filled with clear fluid or fluid that contains blood or white blood cells.
Cysts can form in other organs as well as the kidney; the most common other site is the liver. Current research suggests that liver cysts are associated with the bile ducts or tubules of the liver rather than liver cells themselves. It appears that rather than take the place of functioning liver cells, cysts merely push the liver cells aside. This is why liver cysts don't cause liver failure even though the liver can become quite enlarged due to cysts.
Research has shown that there are at least three components to cyst formation:
Cell proliferation: The cells of a cyst wall reproduce themselves more than do normal kidney cells. This makes the cysts grow in size.
Celullar secretion: Secretion is a way of making fluid. To form a cyst the cells themselves must produce fluid. If there were no fluid produced to fill the cyst, there would merely be a ball of cells.
Abnormal basement membrane: The basement membrane is a very thin layer of tissue the cyst cells sit on. In ADPKD this layer is thicker than usual and is made up incorrectly.
In general, cysts cause problems because of their size and the space they occupy. The size of the kidneys and liver is directly related to how many and how big the cysts are. For example, people with kidneys over 15 cm (6 inches) are more likely to have pain than people with smaller kidneys.
?warning not a pretty sight.. PKD vs normal kidney
A diseased polycystic kidney compared to a normal kidney.
How come I've never heard of PKD before? Is it a new disease?
In the 1700s and 1800s, PKD was often given the label of Bright's disease. This term encompassed any of several kidney diseases marked by high concentrations of protein in the urine. Today, we know that many of the cases of Bright's disease were actually cases of PKD. The first documented case of PKD dates back to Stefan Bathory, the King of Poland, who lived from 1533 to 1588.
In addition, the PKD Foundation is the only organization in the world that focuses on PKD and it was not formed until the mid-1980s. It wasn't until fairly recently that PKD has gained some momentum in raising awareness and funds for the disease.
Another reason many have not heard of PKD is because it is an "internal disorder" — meaning that it does not have a dramatic affect on a person's outward appearance. A person living with PKD may have pain or trauma on their internal organs, yet they maintain a very "normal" physical appearance that does not attract attention or compassion from the unknowing public.