— By Dr. Henri Bianucci and Dr. Perry Jameson
Q: Our 15-year-old cat was recently diagnosed with kidney disease at his yearly checkup. At this time the vet says he is in stage 1. Any suggestions?
The kidneys have many functions and kidney disease implies that they are not performing one or all of these functions normally.
The most familiar function is the removal of waste products that accumulate in the blood as part of normal life. These are filtered from the blood by the kidneys and eliminated from the body in the urine.
At mild increases, most pets are asymptomatic. As these levels increase, however, they cause loss of appetite, nausea, vomiting, oral and gastric ulcers and even neurologic symptoms. The blood urea nitrogen (BUN) and creatinine are the two most commonly measured on routine blood work.
The kidneys help maintain a normal hydration state. We have all experienced times when we did not drink much water during the day and did not have to go to the bathroom, or when we did our urine was darker than normal. This is the kidneys doing their job of conserving water to prevent us from dehydrating. Failing kidneys may lose this ability to conserve water, allowing too much water to leave the body resulting in dehydration if your cat cannot keep up.
They produce a hormone called erythropoietin that tells the bone marrow when to make red blood cells so anemia does not occur.
Your cat’s kidneys even help regulate blood pressure. We do not see hypertension commonly in pets, but those in renal failure are the most common animals to develop it.
Kidney failure is classified as either acute or chronic. In acute disease, there has been a sudden injury to the kidneys from such insults as toxins (such as grapes, raisins in dogs, lilies in cats and antifreeze in both), infections, cancer, obstructions or high blood calcium. Depending on the degree of injury, the kidneys may completely recover, partially recover or not recover at all, resulting in death.
With acute renal failure, there is a sudden increase in renal toxins and this usually results in significant symptoms. Anorexia, vomiting and lethargy are the most common ones.
Chronic renal failure is what your cat most likely has and is defined as a slow progressive loss of renal function. In many patients, it is an incidental finding. When the values have slowly risen, the pet is able to tolerate these increases. Eventually, however, they will reach a level that causes symptoms.
This chronic change may be the result of aging or from a previous injury that went unnoticed. The frustrating aspect of kidney disease is that it is almost always progressive, gradually worsening over time.
Chronic renal failure is broken down into four stages by the International Renal Interest Society. The progression to each stage is based on factors such as the BUN, creatinine, presence of protein in the urine and blood pressure.
It is important to detect renal dysfunction early. Even though we cannot stop the progression, we may be able to slow it down. Urinary tract infections, hypertension, phosphorus levels and proteinuria are the four major issues that can be dealt with to slow progression.
I (Perry Jameson) always recommend a urine culture when first diagnosing chronic renal disease, as this is the easiest to treat and eliminate.
The kidneys depend on blood flowing through them to be able to filter out toxins. As these toxins increase, the kidneys in some patients will respond by increasing blood pressure. Subtle increases help more blood to flow through the kidneys.
There is a tipping point where the blood pressure reaches a level that will begin to damage the kidneys. Keeping the blood pressure at a safe level will not only slow progression of renal injury but also prevent other organs from being damaged such as the eyes (retinal bleeding) and brain (strokes).
The kidneys should not allow protein to leave the body in the urine. If protein is detected, this may indicate high blood pressure in the renal blood vessels even if the systemic blood pressure is normal. Treating to reduce the protein loss may also help slow the disease.
Phosphorus levels often increase with renal disease. Also, make sure these are closely watched and treated if too high.
Another important thing to do is to maintain a normal level of hydration. When dehydrated, the kidneys have trouble filtering the blood. Promote water intake by feeding canned food or getting a pet water fountain. As your cat’s disease progresses, you may be taught how to administer subcutaneous fluids at home.
Talk to your cat’s veterinarian about diets (either pre-made or homemade) designed for cats in the varying stages of renal failure. Certain supplements such as omega-3 fatty acids may be of benefit as well.
Anemia may develop from blood loss associated with gastric ulcers. Acid blockers are often recommended to improve appetite and prevent these ulcers. Lack of bone marrow stimulation by the failing kidneys to make new red blood cells may also result in anemia and require therapy.
It is difficult to predict how rapidly renal disease will progress, but there are ways to keep your cat comfortable and slow down the progression.
Dr. Henri Bianucci and Dr. Perry Jameson are with Veterinary Specialty Care LLC. Send questions to petdocs@postandcourier.com.
