PKD, or polycystic kidney disease, is a genetic condition in which fluid-filled cysts grow throughout the kidneys, gradually enlarging them and impairing their ability to filter blood. It affects roughly 1 in 400 to 1,000 people in its more common form and is the most common inherited cause of kidney failure worldwide, with about 500,000 people affected in the United States alone.
The Two Types of PKD
PKD comes in two forms, and the distinction matters because they differ dramatically in who they affect and how severe they are.
Autosomal dominant PKD (ADPKD) is by far the more common type. It’s typically diagnosed between ages 30 and 50, when symptoms first appear, which is why it’s sometimes called “adult PKD.” You only need to inherit one copy of the faulty gene (from either parent) to develop it. Cysts grow slowly over decades, and the kidneys progressively enlarge.
Autosomal recessive PKD (ARPKD) is rare, occurring in roughly 1 in 20,000 to 40,000 births. It requires both parents to carry the gene. ARPKD is far more severe, often showing up before or shortly after birth. Mortality of 30 to 40 percent has been reported in newborns, primarily from underdeveloped lungs caused by massively enlarged kidneys pressing on the chest cavity during fetal development.
What Causes Cysts to Form
In ADPKD, mutations in one of two genes (called PKD1 or PKD2) reduce the function of proteins that act as sensors on the surface of kidney cells. These proteins normally help cells “know” the shape and size of the tiny tubes they line inside the kidney, keeping growth in check. When the protein’s activity drops below a critical threshold, the affected cell begins to multiply and secrete fluid inward, creating a small pouch that eventually pinches off from the tube and becomes a self-contained cyst.
This is often described as a “two-hit” process. You’re born with one faulty copy of the gene in every cell, but cysts only form in individual cells where the second, working copy also gets damaged over time. That’s why cysts appear gradually rather than all at once, and why the disease worsens with age. Each cyst then expands through two forces: the cells lining it keep dividing, and they actively pump fluid into its center.
Symptoms and When They Appear
Most people with ADPKD have no symptoms for decades. The most common symptom, once it appears, is pain in the back and sides between the ribs and hips. This pain can be brief or ongoing, mild or severe, and it has several possible causes: a cyst bleeding or bursting, a urinary tract infection, kidney stones, or simply the tissue around the kidney stretching as cysts grow.
Blood in the urine is another early sign. Some people notice it on their own; for others, it shows up on a routine urine test. High blood pressure often develops before kidney function measurably declines and can be one of the first detectable clues.
Problems Beyond the Kidneys
PKD is not strictly a kidney disease. Cysts can also grow in the liver, pancreas, and other organs. Liver cysts become more common and more numerous with age, though they rarely cause liver failure.
More concerning is the increased risk of brain aneurysms, which are balloon-like bulges in blood vessel walls that can rupture and cause bleeding. People with a family history of aneurysms or stroke are sometimes screened with brain imaging. About 1 in 4 adults with PKD also develop mitral valve prolapse, a condition where a heart valve doesn’t close tightly. Weaknesses in the colon wall (diverticulosis) are also more common.
How PKD Is Diagnosed
Ultrasound is the standard first-line test, and diagnosis depends on your age and whether PKD runs in your family. If you have a parent with ADPKD and you’re between 15 and 39, finding three or more cysts total across both kidneys is enough to confirm the diagnosis. Between ages 40 and 59, the threshold rises to more than four cysts with at least two in each kidney. After 60, it takes eight or more cysts with at least four in each kidney.
On the flip side, if you’re over 40 and have two or fewer cysts, ADPKD is effectively ruled out. For people without a family history, more cysts are needed for a confident diagnosis since simple kidney cysts are common in the general population as people age. Genetic testing is available when imaging results are unclear or when someone needs a definitive answer, for instance before considering living kidney donation.
How Quickly PKD Progresses
The pace of progression varies widely. Some people maintain adequate kidney function into their 70s or 80s. Others reach kidney failure by their 40s or 50s. The single best predictor is total kidney volume relative to your height and age. The Mayo Clinic developed a classification system (Classes 1A through 1E) that uses kidney size on imaging to estimate how quickly your kidney function will decline. Someone in class 1A has slow growth and a favorable outlook, while class 1E indicates rapid growth and a higher likelihood of reaching kidney failure sooner.
Mutations in PKD1 generally cause more aggressive disease than mutations in PKD2. Men also tend to progress somewhat faster than women.
Treatment Options
There is no cure for PKD, but one medication is FDA-approved specifically to slow the disease. Tolvaptan (sold as Jynarque) works by blocking a hormone that drives cyst growth and fluid secretion. In its pivotal clinical trial, it significantly slowed the increase in total kidney volume, with most of the benefit appearing within the first year of treatment. It’s approved for adults at risk of rapidly progressing ADPKD, and it requires regular liver function monitoring because of a risk of liver injury.
Not everyone with PKD qualifies for or needs tolvaptan. For many people, managing blood pressure aggressively is the most important step to slow progression. Staying well-hydrated, roughly 3 liters of water per day spread throughout waking hours, may help suppress the hormone that tolvaptan targets, though in practice only about 20 percent of patients in one survey actually hit that target. Keeping sodium intake low also helps with blood pressure control, though this requires monitoring because low sodium combined with high water intake can occasionally push blood sodium levels too low.
Pain management, treating urinary tract infections promptly, and monitoring for complications like aneurysms are all part of ongoing care. When kidney function eventually declines to the point of failure, dialysis or kidney transplantation becomes necessary. Transplant outcomes for people with PKD are generally as good as, and sometimes better than, those for people who reach kidney failure from other causes.
Living With PKD
PKD is a lifelong condition, but its slow progression in most cases means many people live full, active lives for decades after diagnosis. Staying on top of blood pressure, drinking plenty of water, and keeping regular appointments for kidney function monitoring are the most impactful things you can do day to day. Contact sports or activities with a high risk of abdominal impact are generally worth avoiding once kidneys are significantly enlarged, since a blow to the side can rupture a cyst and cause sudden pain and bleeding.
Because PKD is genetic, many people face decisions about family planning. Each child of someone with ADPKD has a 50 percent chance of inheriting the condition. Genetic counseling can help families understand the odds and the options available, including preimplantation genetic testing during IVF.