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Veterinary Forum March 2007 (Vol 24, No 3)

Complex task treating older dog with chronic renal disease

by Marie Rosenthal

    ORLANDO, Fla. - As dogs become older, caring for them becomes more complex because of comorbidities.

    Veterinarians, therefore, should evaluate an animal's renal function before prescribing drugs, especially if 50% or more of the drug is excreted through the kidneys, suggested two experts at The North American Veterinary Conference.

    "Chronic kidney disease is a condition in which medications can pose potential risks, and I think it is important to be careful about what you use and how much you use," said Scott A. Brown, VMD, PhD, DACVIM, Josiah Meigs distinguished professor, who heads the department of small animal medicine and surgery at the University of Georgia College of Veterinary Medicine.

    An older dog with renal disease as well as osteoarthritis is fairly common, according to Elizabeth M. Hardie, DVM, PhD, DACVS, professor of surgery in the department of clinical sciences at the North Carolina State University College of Veterinary Medicine. About 20% of dogs show signs of osteoarthritis on a radiograph, and up to 7% of dogs have chronic kidney disease. Scott added that veterinarians sometimes miss early renal disease until the animal develops an acute reaction.

    A real case in Colorado involved George, a fairly healthy, 10-year-old castrated rottweiler with morning stiffness, although he still walked 2 hours each day with his owner. The veterinarian found radiographic signs of osteoarthritis and put the dog on a COX-2 inhibitor, according to Hardie. The veterinarian carefully followed the dog, she said, and the owner reported that the dog seemed more comfortable. So, they continued his therapy.

    After being on therapy for several weeks, the owner and the dog took a long hike in the Rockies, and 48 hours later, George presented to an emergency clinic. He was weak and depressed, with a creatinine of 6.5 mg/dl (normal: 0.5-1.6) and blood urea nitrogen score of 150 mg/dl (normal: 8.8-26). "The tentative diagnosis was acute renal damage or chronic renal failure," Brown said.

    It is likely, he added, that George suffered some dehydration during the long walk, and he probably had renal disease that was missed.

    Hardie said serious adverse events from NSAIDs and other drugs are rare in healthy patients, so many veterinarians do not think about them. But before using NSAIDS in older patients, consider the following risk factors: dehydration, severe blood loss, congestive heart failure, restricted sodium intake, preexisting renal compromise, hypertension and whether they are taking other medications, including complementary medicines, such as herbs.

    "If you have these risk factors, suddenly the rate of complications goes way up," she said. "The more of these you have, the more likely you are to get into trouble."

    Brown recommended following the International Renal Interest Society (IRIS) staging system for chronic kidney disease to ensure that early stages are not missed.

    When deciding therapy for an older dog, Hardie suggested working with the owner to set goals. "What is the goal of therapy? They have a dog with chronic renal failure and they have a dog with really bad arthritis. It comes down to the pet's quality of life. You and the owner have to decide that together. The owner has to be aware of the risks of treatment," she said.

    "A consideration that is important is the financial and time constraints of the owner. You can suggest this gorgeous plan of multimodal therapy and if the owner can't make it happen, it is worthless."

    She said in the case of an animal with multiple conditions, including arthritis, one might consider physical therapy, pain medications, nutraceuticals, dietary changes, acupuncture or low-level laser.

    "Whatever we are going to do, we have to make sure that we carefully screen and follow this patient," she said. "The bottom line for us as veterinarians is that there are no risk-free drugs, and we have to understand what the drugs we are using do."

    For more information:

    Brown S. Schering Chronic Disease Symposium: Chronic renal failure: Medications to use and not to use.

    Brown S, Hardie E. Schering Complex Disease Symposium: Canine chronic renal disease and OA.

    Both presented at: The North American Veterinary Conference; Jan. 13-17, 2007; Orlando, Fla.

    The symposium was sponsored by Schering-Plough Animal Health.

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