Chronic renal failure (CRF) is a common cause of feline illness, especially in older cats. It is also incurable. With the exception of a kidney transplant, it is difficult or impossible to improve kidney function in cats with chronic renal failure. But it is possible to slow the progression of renal failure and improve the quality of life through dietary and drug interventions.
The benefits of dietary modification in CRF have been well documented. Protein, when metabolized, gives rise to toxins that the failing kidneys cannot properly excrete. By reducing the amount of protein in the diet, the toxin level is lessened, and this helps combat weight loss, poor appetite, vomiting and lethargy. In the past, choices were very limited with regard to these diets for cats. Recent veterinary studies confirmed that cats fed prescription diets feel better and live longer.
In addition, potassium supplements now available in palatable forms seem to be helping cats diagnosed with CRF. Hypokalemia (low blood potassium) contributes to kidney failure progression. Potassium supplements aid in addressing general muscle weakness affecting cats with kidney disease.
Cats with diseased kidneys have difficulty conserving water-soluble vitamins due to the excessive amount of urine produced by the failing kidneys. Work with your veterinarian to select a multi-vitamin appropriate for your cat.
A recent study has shown that the severity of proteinuria (excessive protein in the urine) is related to survival in cats with chronic renal failure. Proteinuria can be detected by a simple urine test. Cats who lose excessive protein in their urine can be treated with a drug, benazepril. This can restore the urine protein level to normal and increase survival.
Phosphorus is filtered from the bloodstream by the kidneys. When the kidneys begin to fail, the phosphorus levels begin to rise. This can lead to further kidney damage. Limiting phosphorus consumption appears to slow the progression of CRF in humans and dogs, and there is evidence that dietary phosphorus restriction also limits renal injury in cats with CRF. Prescription diets designed for cats with kidney failure contain reduced levels of phosphorus, however, the level may not be restricted enough.
Cats with CRF need to drink large quantities of water to maintain hydration – or run the risk of becoming dehydrated, which can have additional harmful effects on the kidneys. While there are ways to encourage additional water intake (feeding canned food rather than dry food, adding water or broth to the food), often the fluid intake for cats with CRF is inadequate. Some CRF cats require subcutaneous (under the skin) fluids given every day. If the cat does well, it might be possible to decrease the frequency to every other day, or even less frequently, depending on how the cat is feeling at home.
High blood pressure, detected in almost 20 percent of cats with CRF, is a major risk factor. These cats should have their blood pressure evaluated regularly and if hypertension is detected, treatment with amlodipine is recommended. Most cats respond readily to this medication. Hypertensive cats need life-long therapy to keep their blood pressure under control.
Many cats with CRF become anemic because the kidneys produce a hormone, erythropoietin, that instructs the bone marrow to manufacture red blood cells. As the kidneys fail, they produce inadequate amounts of this hormone, and the red blood cell level drops, resulting in anemia. Anemia contributes to the lethargy and poor appetite.
A genetically engineered form of human erythropoietin given to cats can dramatically reverse the anemia. However, this hormone can have serious side effects: some cats will produce antibodies against this hormone because the hormone is of human origin. These antibodies not only attack the human erythropoietin, but whatever remaining feline erythropoietin is present. Cats develop sudden, severe anemia as a result and require blood transfusions to keep them alive.
Many advances have been achieved regarding the treatment of chronic renal failure. Treatment must be tailored to the individual cat. Although CRF is not curable, many cats can live for years after diagnosis if treated appropriately.
- By Arnold Plotnick, DVM, board-certified in feline medicine and internal medicine. He operates the Manhattan Cat Specialists practice in New York City and can be reached through his website: www.manhattancats.com.