Exertional Myopathy in Small Animals
(Rhabdomyolysis, Tying-up, Monday morning disease)
This acute exertional myopathy of racing Greyhounds and working dogs is characterized by muscle ischemia secondary to exercise or excitement. Avascularity and lactic acidosis cause muscular lysis, myoglobin release, and a nephropathy.
Clinical signs include muscle pain and swelling 24–72 hr after racing. Severe cases are characterized by stiffness, hyperpnea, collapse, myoglobinemia, and acute renal failure. Urinalysis reveals myoglobinuria; serum potassium, phosphorus, and muscle enzymes are increased. Treatment includes supportive care such as IV fluids, bicarbonate, body cooling, rest, and muscle relaxants (eg, diazepam). Prognosis depends on severity. (Also see Exertional Myopathies in Horses.)