In this episode of the Disease Du Jour podcast, Thomas Divers, DVM, DACVIM, DACVECC, discussed kidney disease in horses. He covered acute versus chronic kidney disease, their clinical presentations, treatment and management options, and more.
This episode of Disease Du Jour is brought to you by Equithrive.
Acute vs. Chronic Kidney Injury
Acute kidney disease in horses often results from nephrotoxic drug administration or hypotension, shock, or systemic illness that causes decreased blood flow to the kidneys. Less commonly, acute kidney disease can result from infection, such as leptospirosis, though this is more common in Europe than in the U.S.
Chronic kidney injury can occur secondary to acute injury. “It could be that the acute kidney injury case recovered partially, but not all the nephrons came back to normal,” Divers explained. “Then over time, due to stress on the remaining nephrons, chronic kidney injury occurred and chronic renal failure.”
Chronic kidney disease can also result from congenital abnormalities, chronic obstruction due to stones (common in racehorses), and glomerulonephritis.
Acute Kidney Injury and Failure
Divers explained that acute kidney injury refers to any acute injury to the kidney that may or may not go into failure. Acute kidney failure is an acute kidney injury that has damaged enough of the functional nephrons to affect the horse’s clinical appearance.
Acute kidney injury is common in horses, and many cases do not progress to failure. Appropriate fluid and drug therapy to improve blood pressure and renal blood flow can make a positive difference. However, “I think that a lot of the factors are outside the veterinarian’s control,” said Divers about why some horses progress to failure while others do not. “Some of these horses are just so hypotensive, and even with appropriate drug therapy, it’s hard to get their blood pressure up.” He noted that providing too many nephrotoxic drugs while treating the primary disease or overhydrating the horse can contribute to acute kidney disease.
Acute kidney injury often does not cause clinical signs. Horses might present with hematuria (blood in the urine). Divers said horses might have decreased or increased urine production, but this is difficult to detect because of how horses are housed.
The most common clinical signs of acute kidney failure are decreased appetite and depression. Rarely, horses will present with colic, which is likely related to kidney swelling. Uremic encephalopathy—or neurologic signs associated with the buildup of ammonia—is also possible.
“When I have seen that, it’s usually a grave prognosis,” said Divers. “And when I’ve seen colic associated with acute kidney failure, swelling of the kidney, it’s a guarded prognosis.”
The main treatment option for horses in the failure stage is fluid therapy to correct dehydration. Divers warned not to overhydrate the horse, which can produce edema in the kidneys and elsewhere. It’s also important to treat the primary disease in horses with kidney failure due to systemic illness.
Chronic Kidney Disease
Clinical signs of chronic kidney disease are slowly progressive. Horses might display weight loss or decreased appetite, but not as dramatically as with acute renal failure. Young horses with a congenital abnormality might look underdeveloped compared to herd mates of the same age. Glomerulonephritis can cause ventral edema.
Divers explained that while veterinarians can treat acute kidney disease, “with chronic, you can only do so much because the kidney has become fibrotic.”
Nutrition is important in these cases to counteract weight and muscle loss. Divers recommended feeding a moderate protein diet with plenty of calories. Access to fresh water is important to ensure the horse doesn’t become dehydrated. It’s also important to avoid nephrotoxic drugs.
“It’s not a perfect equation, but I’ve found that if the creatinine is less than 4.2 or so, or 4.0, in a horse with chronic renal failure, and the horse is still eating well, and you can avoid all these other risk factors (NSAID administration, dehydration, aminoglycosides, tetracycline), they can live for several years, and the stallions can maintain fertility in many cases, and the mares can be bred and conceive,” said Divers, noting that this is just a guideline and may vary by horse. “If it’s a more rapid decline, it’s going from 3.0 to 3.5 in six months, and then it’s up to 4.0 in nine months, that’s a bad finding.”
Listen to the podcast episode to learn more.
About Dr. Thomas Divers
Thomas Divers, DVM, DACVIM, DACVECC, earned his DVM from the University of Georgia in 1975 and completed an internship in large animal medicine at the University of California, Davis. Divers returned to the University of Georgia for a residency in large animal internal medicine and ambulatory practice, followed by two years as an assistant professor in large animal medicine and ambulatory practice. Divers then moved to the University of Pennsylvania for 10 years, where he was an associate professor of large animal medicine and served as chief of the section of medicine at the UPenn’s New Bolton Center. In 1990, Divers moved to Cornell University to serve as the Rudolph J. and Katharine L. Steffen Professor of Medicine in the Section of Large Animal Medicine. He is a diplomate of both the American College of Veterinary Internal Medicine and the American College of Veterinary Emergency and Critical Care. Divers retired recently but still consults on cases, conducts research projects, and provides lectures to veterinarians and students. He has been the recipient of teaching awards at four universities and has received the Educator of the Year Award from both the AAEP and ACVECC.
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