Retrievers are among the most popular dog breeds in the world. The Labrador retriever has been the most commonly registered breed in both the American Kennel Club and the Canadian Kennel Club for more than a decade, and the golden retriever consistently ranks in the top five to 10 breeds.1,2 Retrievers typically have an active lifestyle, and many are engaged in hunting, field competition, or other strenuous activities such as agility or search and rescue work. Retrievers presented to veterinarians for perceived exercise intolerance may have decreased strength, speed, or stamina compared with other dogs or compared with their own usual performance standard. Signs can sometimes be subtle, with suboptimal performance detected by the owner or handler, but not detectable by inexperienced observers. Alternatively, the signs may include profound exercise-induced weakness, episodes of collapse, or even death following exercise.
This article focuses on the conditions associated with exercise intolerance in retrievers. The conditions and the principles of evaluating these patients that we outline apply to other breeds of dogs as well, but we emphasize those disorders most likely to be found in the retriever breeds.
A complete history investigating abnormalities in every body system is important (Table 1). Whenever possible, a veterinarian should observe the dog while it is manifesting what the owner perceives as exercise intolerance. When this is not feasible, details regarding the type, duration, and intensity of exercise that result in exercise intolerance and a clinical description of the exercise intolerance itself should be collected from the owner or handler. In some cases, a videotape of the dog exercising can help to characterize the perceived exercise intolerance.
Table 1. Exercise Intolerance Supplemental History
Many dogs with exercise intolerance have abnormal physical examination findings at rest. Careful physical examination may detect abnormalities that lead to a diagnosis. Complete respiratory, cardiovascular, musculoskeletal, and nervous system examinations should be performed, as well as thorough abdominal palpation. When the patient history, physical examination, and routine laboratory evaluation do not provide a diagnosis, it may be necessary to exercise the dog in order to examine it while it is exercise intolerant.