Unfortunately, cats’ kidneys tend to wear out. As discussed in a previous column, many diseases can affect these organs. Unlike other vital organs, such as the liver, the kidneys are not capable of regenerating. Once started, degenerative kidney disease progresses.
Clinical signs associated with kidney disease can include increased thirst, increased urination, weight loss, dehydration, dental disease, vomiting and loss of appetite.
“Chronic tubulointerstitial nephritis” is the medical term for the slowly progressive loss of kidney function found in older cats. It is the most common disease of cats over 10 years old.
As a cat ages, the kidneys scar and become smaller and less efficient at filtering the blood and preserving water balance in the body. The progressive loss of kidney function can vary depending on the individual animal and the amount of nursing care an owner is willing or able to do. The goals of treatment are to maintain hydration and electrolyte balance, keep blood-waste product levels down, prevent anemia and control secondary infections.
Although veterinary diets with lower protein levels have been developed for cats with kidney disease, the amount of protein in these diets is controversial. Abnormal levels of protein waste products build up in the blood with kidney disease, but cats with kidney disease lose more protein and have a harder time maintaining proper body condition. The dietary needs of a cat with kidney disease are quite different than of cats with bladder disease, so be sure you and your veterinarian are addressing the correct part of the urinary tract when choosing a diet for either condition.
Fluid therapy is the cornerstone of kidney disease treatment. Cats with very high levels of metabolic waste products in their blood (elevations of BUN and creatinine) often require diuresis, an aggressive type of IV-fluid therapy, for several days. Long-term treatment with fluids inserted under the skin is used after diuresis and with cats whose kidney function is not as severely affected. At my clinic we teach owners to administer subcutaneous fluids at home as part of kidney disease management.
Maintaining proper levels of minerals in the blood is important in controlling kidney disease. Two minerals that need to be closely monitored are potassium and phosphorus. Cats with kidney disease tend to have low potassium levels and high phosphorus levels. Potassium supplementation and phosphate binding agents are utilized when needed. A drug called calcitriol is used by some veterinarians to control phosphorus and calcium levels.
Cats suffering from kidney disease can become anemic, having low numbers of red blood cells, because the kidneys stop producing erythropoietin, a hormone that stimulates the bone marrow to produce red blood cells. Erythropoietin can be supplemented by injection when the red blood cell count gets too low. This is another treatment owners can be taught to administer at home.
Benazepril is another medication used in some cats with chronic kidney disease. This drug helps open blood vessels and can decrease blood pressure and promote blood flow through the kidneys. Antacids, appetite stimulants and antibiotics can also be used with chronic kidney disease patients when warranted. Several supplements and probiotics are designed to help keep the kidneys functioning as well as possible. Since cats are often challenging to medicate, veterinarians need to choose which treatments provide the most benefit, are the least stressful to administer, and maintain the best quality of life for owner and cat.
Early recognition of kidney disease and appropriate treatment lead to the best response and increased longevity for affected cats. Unfortunately, even if a cat is being well maintained on fluid therapy and other treatments, kidney disease will invariably progress past a treatable stage. This could take weeks, months or years depending on the specific situation. Cats with kidney disease should be monitored by a veterinarian at least every six months, as should any senior cat over the age of 12.