Complete Care for Your Aging Cat - Amy Shojai [110]
“Kidney disease very often is intertwined with high blood pressure and thyroid disease,” says Dr. Little. Hypertension in cats, though only recently recognized, is quite manageable. “Cats with kidney insufficiency have a derangement of the physiological system that helps monitor blood pressure and it can get out of whack, and they get high blood pressure from it.” Many cats have kidney disease, hypertension, and hyperthyroidism at the same time.
About one in four cats with chronic renal failure or hyperthyroidism also develop hypertension. “We don’t wait until they’re ill. We do blood-pressure checks routinely on any older cat with a blood-pressure cuff,” says Dr. Little. The Doppler blood-pressure monitor is currently considered the most accurate machine for use on cats. An inflatable cuff is placed on the cat’s foreleg, and a transducer reads reflected ultrasound signals bouncing off moving red blood cells.
Getting an accurate reading can be tough, though. Normal systolic blood pressure (during heart contraction) is about 110 to 125. Stress from going to the hospital can make the cat’s blood pressure go higher and cause an inaccurate reading. Sedation also interferes with accuracy. Often, multiple readings over several days must be averaged to get the best picture of the cat’s situation. “When their high blood pressure is controlled, they often feel better and do better with their kidney failure. So they’re intertwined, it’s hard to separate them,” says Dr. Little.
Diet Therapy
Chronic renal failure will progress, regardless of what you do, says Dr. Carey. “Our objective is to slow the progression.” Medications help normalize the blood, and special therapeutic diets are prescribed that reduce the workload of the kidneys.
Many of the “regular” senior diets for cats offer a nutrient profile that reduce the risk factors associated with kidney disease, says Dr. Davenport. Dietary phosphorus, sodium, protein, and essential fatty acids are of particular importance, as well as ensuring the diet does not acidify the urine. The point is emphasized because regular feline maintenance diets often do acidify the urine to reduce the risk of certain kinds of crystals, called struvite. Calcium oxalate crystal formation that typically block the kidney ureters is promoted by an acidic diet, though.
Usually the first step is a special diet designed to minimize the amount of stress placed on the kidneys, says John F. McAnulty, DVM, an associate professor of surgery at the University of Wisconsin. “I’ve seen cats that were not doing well that start to gain weight, and really seem to be a lot more energetic on the diets.”
Nearly all the major pet food companies offer therapeutic diets for kidney disease, and most also have one for “early stage” and another for a more advanced stage of the disease. Most restrict phosphorus and sodium, and provide a low to moderate level of highly digestible protein to help relieve the burden on the organs. “Protein and phosphorus are linked together, so when you try to control dietary phosphorus, you also reduce dietary protein,” says Dr. Davenport.
Adding the right type of fiber to the diet also reduces the workload of the kidneys, says Dr. Carey. Here’s how it works. Failing kidneys leave behind nitrogen waste in the blood. Certain kinds of bacteria trap this nitrogen in the intestine. Feeding a fermentable fiber to the cat maintains the health of these beneficial bacteria. “You can shift the excretion of nitrogen from the kidney to the intestine enough to help the body,” says Dr. Carey.
Most cats with renal failure lose their appetite, and most of these diets are not tremendously palatable, says Dr. McAnulty. Some cats refuse to eat the therapeutic diet. You can then offer other brands and try to find a kidney diet your cat will accept. In many cases, though, you must give in to the cat’s preferences. “You have to cut your losses; you are better off feeding a sub-optimal diet than you are starving it.”
Feeding For Health