Exertional Rhabdomyolysis in Dogs

Racing dogs are one of the groups most at risk for exertional rhabdomyolysis.
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Exertional rhabdomyolysis is a metabolic disease caused by overexertion that’s seen primarily in athletic and working breeds, particularly greyhounds and sled dogs. It’s a potentially life-threatening condition that results from a dog overworking to the point that his muscles become damaged at the cellular level. This disease can look similar to heat stroke, according to Dr. Suzanne Stack, DVM, with symptoms that can include heavy panting, muscle tremors, irregular heartbeat and collapse.

Hyperacute Exertional Rhabdomyolysis

This condition is usually classified according to three levels of severity. The most severe level is hyperacute rhabdomyolysis, which is characterized by extreme distress, swollen muscles that are painful to the touch and general muscle pain. A dog with hyperacute rhabdomyolysis might have difficulty standing or lying down, and will sometimes drag the hind legs while walking. High levels of myoglobin cause red discoloration of the urine. A dog showing signs of hyperacute rhabdomyolysis should receive immediate medical attention. This condition is extremely dangerous, and can result in death from acute kidney failure within 48 hours. Dogs who survive a bout with this illness will face a slow recovery of about two months, and may experience permanent muscle loss.

Acute Exertional Rhabdomyolysis

Acute rhabdomyolysis generally has a better prognosis than hyperacute, according to Vetstream.com, but a dog who suffers from this condition might still endure a long recovery. Dogs with this form of the illness appear distressed following a race or other prolonged exertion, and are in obvious pain when touched along the back and hind leg muscles. Although the urine might not be discolored, tests will still show myoglobin in the urine.

Subacute Exertional Rhabdomyolysis

Subacute rhabdomyolysis is the least severe form. While not as dangerous as the acute or hyperacute forms, it can progress in severity if the dog is subjected to subsequent heavy exertion. A dog suffering this form of the disease might be running more slowly or performing at less than optimal levels, and pain in the muscles of the saddle area can develop as much as 24 to 72 hours after the race. Urine analysis will show myoglobin in the urine, and might also show increased pH. Subacute rhabdomyolysis is rarely fatal, but recovery will require about four to seven days of therapy, according to VetStream.com.

Affected Breeds

Working dogs and racing dogs are the most likely to encounter this disease. Although exertional rhabdomyolysis is mostly seen in sled dogs and racing greyhounds, it can also occur in other working breeds such as sheep dogs, bird dogs and coursing dogs. According to VetBook.com, both the greyhound and the old English sheepdog have a predisposition toward this condition. Although less common in non-working breeds, this illness is occasionally seen in escaped pet dogs who have run away from home.