WHEN NORMAL IS NOT NORMAL: CHRONIC KIDNEY DISEASE IN DOGS AND CATS
Chronic kidney disease is one of the most common disorders affecting older pets. As they get older their kidney function can decline. Kidneys act like a filter to remove wastes and extra fluid from the body. They filter the blood each day to make urine, which contains wastes and extra fluid. This prevents buildup of wastes to keep our pets healthy. Other than age related changes, specific causes of chronic kidney disease include infections, kidney stones, toxicity, cancer, and protein loss in the urine ( a disease called glomerulonephritis). Nonsteroidal medications used to manage arthritis are sometimes implicated in kidney disease. Signs of kidney disease can come on suddenly or be insidious. They include weight loss, decreased appetite, increased drinking and urination (such as having accidents inside the house), vomiting, and bad or uremic breath, as normal metabolic waste products the kidneys eliminate are not being removed, causing sores in the mouth. Some pets can be in the early stages of kidney disease and show no signs. The International Renal Interest Society (IRIS) has come up with 4 stages of chronic kidney disease. They are based on the level of creatinine in the blood. Creatinine is a normal breakdown product of muscle metabolism that is normally filtered and removed by the kidneys. When this is consistently elevated, and the pet is not dehydrated for some other reason, chronic kidney failure is the diagnosis. A new development in the diagnosis of kidney disease is the SDMA test. SMDA (symmetric dimethyl arginine) is another breakdown product metabolized by the kidneys but is not affected by muscle mass. It can detect kidney failure earlier than creatinine and is now included in our bloodwork. It can be useful in a very thin cat or dog that has kidney disease not detected by the creatinine, but uncovered by the SMDA test. The Iris guidelines values for stage one place creatinine in the NORMAL range of many analyzers. This means that a pet with a high normal creatinine could be in the early stages of kidney disease. This is why we do follow up bloodwork to see if the values are stable or rising. We will also want to do a urinalysis. A cat or dog with a high creatine could be dehydrated from another cause, but If the urine is concentrated, the kidneys are working and we have to look for another cause of the dehydration. But if the urine is dilute, the high normal creatine may be a sign of early kidney disease. If a cat or dog is diagnosed with kidney failure, there are several things we could do to help. One option is to look for underlying causes with a urine/protein ratio ( this is different and in addition to the regular urinalysis), x-rays, urine culture, and checking blood pressure. Kidney disease can cause high blood pressure, or high blood pressure can also damage the kidneys. If blood pressure is consistently high (multiple checks over 2-3 weeks) or there is significant protein loss in the urine, supplemental medications can be added. However, without doing a lot of additional testing, starting a kidney friendly diet with modified protein, lower phosphorus, and omega fatty acids can help slow down the progression of chronic kidney disease. Studies have shown that pets with kidney disease that eat these diets LIVE LONGER than pets that do not. It is important to get them started on the special diet earlier rather than later, because a pet in later stages of kidney disease may not have a normal appetite and be as willing to switch to a new food. In some cases, especially at later stages of disease, pets (especially cats) can benefit from regular subcutaneous fluids, which keep them hydrated and increase the blood flow to the kidneys so they can do their job. Owners can learn to do this at home. Some pets will also benefit from anti nausea drugs that help with appetite and vomiting. As kidney disease progresses, phosphorus levels can rise, which can be managed with medications called phosphate binders. Potassium can also be lost in the urine, and providing extra potassium may be necessary. As you can see, regular blood testing can help detect these changes so they can be addressed. In summary, kidney disease is common in our older companions, but there are ways we can detect it earlier so we can intervene. We recommend bloodwork on all pets older than seven years old to help them live a long and healthy life. Remember to discuss it with us at your pet’s next visit.
Thank you to Dr. Travis Freiwald for this wonderful information.