Polycystic Kidney Disease in Horses: Cysts, Kidney Function, and Prognosis

Polycystic kidney disease in horses refers to the presence of multiple fluid-filled cysts within the kidneys. These cysts can replace or compress normal kidney tissue, which may reduce the kidneys' ability to filter waste, balance electrolytes, and conserve water. In horses, cystic kidney disease is considered uncommon, and many cases are recognized only after kidney values rise or ultrasound shows structural changes.

Kidney disease in horses often stays quiet until a large amount of kidney function has already been lost. That is why some horses with cysts look normal early on, while others are brought in for weight loss, poor performance, increased thirst, or changes in urination. When cysts are extensive, horses may develop chronic kidney disease and the related problems that come with it, including azotemia, dehydration risk, and mineral imbalances.

In some horses, cystic disease may be congenital or inherited. A PKHD1-associated condition has been described in Franches-Montagnes horses, linking fibrocystic disease biology in the liver and kidneys. In other horses, a single kidney cyst or a few cystic changes may be found incidentally on imaging and may not behave the same way as diffuse polycystic disease.

Because the outlook depends on the amount of remaining kidney function rather than the word "cyst" alone, your vet will focus on the whole picture: bloodwork, urine concentration, ultrasound findings, hydration status, and whether the horse is stable or declining.

True polycystic kidney disease is usually thought of as a developmental or inherited problem rather than something caused by routine management. In horses, published evidence is limited because the condition is rare. A PKHD1-associated fibrocystic disorder has been described in Franches-Montagnes horses, which supports a genetic basis in at least some equine cases.

That said, not every kidney cyst seen on ultrasound means a horse has inherited polycystic kidney disease. Some horses may have isolated renal cysts, asymmetric kidney changes, or chronic scarring that can look cystic. Your vet may need to sort out whether the finding is an incidental cyst, congenital cystic disease, or chronic kidney damage from another cause.

Other kidney problems in horses can also reduce kidney function and may exist alongside cysts. These include prior toxin exposure, dehydration, reduced blood flow to the kidneys, severe infection, leptospirosis, or medication-related injury, especially when a horse is already compromised. Those conditions do not create classic inherited PKD, but they can affect prognosis because they reduce the amount of healthy kidney tissue available.

For pet parents, the key point is that cysts are only part of the story. The practical question is how much kidney function remains and whether the process appears stable, progressive, or part of a broader renal disorder.

Diagnosis usually starts with a physical exam and baseline lab work. Your vet will often recommend a chemistry panel to look at creatinine, urea nitrogen, electrolytes, calcium, phosphorus, and acid-base related changes, along with a CBC and urinalysis. In horses with kidney disease, urine may be inappropriately dilute, and bloodwork may show azotemia once enough kidney function has been lost.

Abdominal ultrasound is one of the most useful next steps because it lets your vet assess kidney size, contour, echogenicity, and whether cysts are present in one or both kidneys. Ultrasound also helps distinguish diffuse cystic change from other structural problems. Current equine kidney consensus guidance supports imaging as an important part of evaluating chronic kidney disease.

In selected cases, your vet may add urine protein testing, culture if infection is suspected, SDMA, repeat bloodwork over time, or referral imaging. Kidney biopsy is not routine for every horse, but it may be discussed in unusual or unclear cases when the result could change management. Biopsy decisions are individualized because they add cost and some risk.

Typical diagnostic cost ranges in the United States in 2025-2026 are often about $300 to $800 for an exam, farm call, CBC/chemistry, and urinalysis, and about $500 to $1,200 when abdominal ultrasound is added. Referral workups, serial monitoring, or hospitalization can push total costs higher.

There is no guaranteed way to prevent inherited or congenital cystic kidney disease once a horse is genetically affected. If a breeding line is known to carry a fibrocystic disorder, breeding decisions and pedigree review matter more than day-to-day management. In breeds with documented inherited fibrocystic disease, your vet and breed resources may help guide risk discussions.

Even though you cannot fully prevent true PKD through routine care, you can help protect overall kidney health. Good hydration, prompt treatment of illness, careful use of medications that can affect the kidneys, and regular veterinary monitoring all reduce the chance that a horse with limited kidney reserve will decompensate.

Ask your vet to investigate persistent weight loss, increased drinking, increased urination, or poor appetite rather than waiting for signs to become severe. Earlier workups may not stop cyst formation, but they can identify kidney dysfunction sooner and give your horse more management options.

For pet parents managing a horse already diagnosed with renal cysts, prevention shifts toward preventing complications. That means keeping follow-up appointments, tracking water intake and body condition, and contacting your vet quickly if appetite drops, dehydration appears, or the horse seems dull or weak.