Chronic renal insufficiency - Other treatments
Chronic renal insufficiency in cats is not a curable disease. Our goal is to manage the symptoms so that the cat is comfortable, and to slow down the progression or delay the onset of more serious clinical disease. In order to do this we take a multi-faceted approach.
We commonly send cats home to have subcutaneous fluids (saline or lactated ringer's solution) given at home by the owners. This is a very effective way of rehydrating these kitties and flushing some of the toxins from the system. Giving subcutaneous fluids is not difficult, but does involve a needle. Most owners, once they have tried it a couple of times, are very comfortable with the procedure and find it much easier than they anticipated. Alternatively, we will have a patient in to the hospital 2-3 times a week for a brief visit to receive fluids. These visit typically take 5-10 minutes and the fluids are administered by a technician. There is no time scheduled with the veterinarian.
What do fluids do? Two things - they rehydrate the animal and help to dilute and flush out accumulating toxins. We know that these cats are dehydrated. Dehydration in people causes fatigue, muscle cramps, headaches, inappetance, and a general feeling of sickness. It makes sense that if we can relieve the dehydration in our renal disease cats that we can make them feel better. Cats that feel better eat more and exercise more. Additionally, we are usually helping to decrease the phosphorus levels (See "Diet'" page). Some veterinarians will add potassium to the fluids as well, giving even more benefit.
One thing that we rarely see in normal cats but is relatively common in cats with chronic renal insufficiency is constipation. This is usually a direct effect of dehydration. Dehydrated cats are trying to save every scrap of water they can, since the kidneys are not doing the job. One source of water is the stool in the colon. The colon sucks the stool dry. As well, the lining of the colon (which is normally wet and slippery with mucus) becomes dry and sticky, making it hard to pass a bowel movement.
Low potassium levels can be both a sign of CRI and a precipitating factor in its development (in other words, it can be a result of renal disease and can also make it worse). Some veterinary urologists recommend supplementation with potassium before it falls below normal blood levels. Why?
The body likes to keep potassium levels in the blood within a pretty narrow range. If the kidneys are failing to keep potassium in the body and there is no supplementation in the diet, blood potassium naturally has to fall over time. And we have to keep in mind that most of these cats are not eating properly; their dietary intake of potassium falls off as they eat less. So they really do get a double whammy - less potassium going into the body, and more potassium lost in the urine. In response to a decrease in blood potassium, it is pulled out of body cells and into the bloodstream to keep the blood potassium within the normal range.
The result can be a depletion of potassium within the body cells with normal blood potassium levels. Potassium is critical for the function of muscle, among other things. If the muscle cells become very potassium-depleted they become very weak. Veterinarians often see this show first as neck weakness, and the cat will come in with "ventroflexion of the neck". Basically, the neck muscles are too weak to support the head, and the cat's head bends down toward the chest. Potassium supplementation reverses this problem.
As well, low potassium levels seem to actually impair the filtration ability of the kidneys. Not only is the kidney disease causing potassium loss, but low potassium if causing more kidney damage. This becomes a vicious circle.
The objective is obviously to prevent this cell depletion from happening in the first place, in the hope that this will help to delay the progression of the disease. Certainly potassium supplementation has been a mainstay of renal disease treatment for some time, and it is my opinion that all cats with renal insufficiency should be on oral potassium. Dietary supplementation with potassium is relatively easy - it's a powder added to the food.
The use of calcitriol deserves a page of its own, and will be coming shortly.
Agiotensin-converting enzyme (ACE) inhibitors dilate the blood vessels in the kidneys. This decreases the blood pressure and allows better blood flow to the kidneys without damaging them further. Several studies have been done and are currently underway to try to determine whether ACE inhibitors have an effect on the progression of renal disease in cats. Results to this point are not conclusive, but appear to show that only cat with abnormally high urine protein would benefit. At this time I am restricting my recommendations for ACEI therapy to those cats with a urine protein/creatinine ratio over 0.4.