By Dr. Luke Peterson, DVM
For those of us in snow country, an interesting phenomenon occurs in winter. We see a much greater incidence in urinary tract infections as owners have the ability to identify bloody urine. From a clinical mindset there are three things that can be in urine that make urine look “bloody”. The first and most obvious is blood, the second and third are less common but often of greater concern, hemoglobin and myoglobin. Hemoglobin is the protein in red blood cells responsible for carrying oxygen to other cells. Hemoglobin is observed in urine when there is a pathologic destruction of red blood cells in the body. Myoglobin is similar to hemoglobin as it binds iron and oxygen in muscle cells and allows for greater oxygen capacity in muscle cells for more efficient energy production. Myoglobin is found in urine when there is pathologic destruction of muscle cells. Aside from the destruction to muscle cells, myoglobin can have greater consequences on kidney health. Potential causes for muscle cell damage include autoimmune diseases, infections, nutritional deficiencies, hyperthermia, hormonal diseases, and exercise induced over-use.
Exercise induced muscle damage, more accurately known as exertional rhabdomyolysis, has been given many different names over the years: Monday Morning Disease, Tying Up, Canine Cramps. The disease has long been recognized in the days of working horses that would have Saturday and Sunday off and start back to work Monday with heavy pulling. As more people have moved from the country to cities and suburban areas without nearby places to routinely condition their dogs during the week, this disease has started becoming more common in “weekend warrior” dogs. Although it can also be seen in well-conditioned dogs when pushed to great physical extremes such as long days hunting or trialing in high heat and humidity. Symptoms for canine exertional rhabdomyolysis include generalized muscle pain (mostly in the back and rear legs), stiff gait, uncoordinated walking or running, distress, and collapse. Occasionally seizure like shaking can be seen and this disease is sometimes misdiagnosed as hunting dog hypoglycemia or “sugar fits”. One of the tell-tale signs of excessive muscle damage is dark red to brown color in the urine from the myoglobin. This can occur the same day as the over exertion but may not be apparent until the following day. The same result can be seen in any mammal that overexerts its muscles’ capacity to work and causes cellular death to the muscle cells. In fact, there is a popular new exercise program for people called “Cross-fit”. I haven’t looked into it much, but it sounds like it may be the fitness program you’re put on if you end up in hell. One of my associates recently engaged in this program and told me the morning after her first workout she was urinating myoglobin.
Aside from the muscle damage, the real concern we have for these dogs is the effect that myoglobin released from damaged cells has on the kidneys as it circulates in the blood stream. Myoglobin causes acute injury to kidney cells as it accumulates in the filtrated portion of fluid prior to becoming urine. The longer myoglobin is present, the more damage occurs. Once myoglobin in the urine is observed, the best treatment is to have intravenous fluids given to flush out the myoglobin before it accumulates. If you catch it early, IV fluid treatment prevents most dogs from incurring any long term kidney damage.
The best prevention for this is proper conditioning, limiting heat stress, and providing breaks during high temperature extremes. Vitamin E has been identified as an important nutrient to prevent muscle damage, and nutritionists recommend 200-400 IU of Vitamin E per day for dogs around 30 pounds. Most commercially produced dog food has adequate levels of Vitamin E and list levels in the guaranteed analysis on the bags. Note that there are many forms of Vitamin E. The active form of Vitamin E is Tocopherol, so be sure when checking ingredients that the Vitamin E is identified as being in that form. Dogs not on commercial dog food or being fed mainly meat based diets often deficient in Vitamin E and would benefit from supplementation. Vitamin E is typically available in 200 IU capsules. The question of whether additional vitamin E beyond the 200-400 IU per day would be beneficial has been evaluated by researchers studying this disease in racing sled dogs. They have consistently found excessive Vitamin E supplementation (1000 IU per day) offers no benefit in prevention and actually decreased the performance of sled dogs during performance. In general, if you’re unsure what level of Vitamin E your hounds are receiving, supplementing an additional 200 IU per day will probably not suppress their performance and there may be individuals that benefit from this supplementation.
In summary, the best ways to prevent and treat exertional rhabdomyolysis in running dogs are:
- Feed a diet providing around 400 IU of Vitamin E per dog per day
- Limit exercise in dogs that have been laid up for long periods of time and gradually increase their activity during to reach proper conditioning
- Avoid heat stress and be sure to have cooling methods nearby for overheated dogs
- Monitor dogs during strenuous exercise and the day after for brown or red colored urine
- If you see discolored urine, be sure to get them to the vet immediately for IV fluids