Chronic renal insufficiency

What is chronic renal insufficiency?

It’s a condition that occurs when 75-85% of kidney function has been lost. Animals over 7 years of age are most commonly affected. Normal kidneys get rid of metabolic waste and will concentrate urine by reabsorbing water. When kidneys start to fail, more water is lost in urine so your pet has to drink more to compensate. Dehydration will occur despite an increase in water consumption because there is water loss in urine.

Also, accumulation of waste in the bloodstream (uremia) can cause symptoms such as anorexia, vomiting and/or nausea.

Unfortunately, chronic renal insufficiency is progressive and irreversible. Because diagnosis is usually made much later than the original insult to the kidneys, a primary cause is rarely identified. However, we are aware that certain situations can further damage the kidneys such as dehydration, administration of nephrotoxic drugs, urinary tract infections, kidney stones, hypertension and proteinuria.

How is chronic renal insufficiency diagnosed?

Relating your pet’s symptoms can often make the veterinarian suspicious. The physical exam could include unspecific signs such as weight loss, weakness, dehydration and smaller kidneys.

To confirm diagnosis we have to perform different tests.

A blood sample will show an increase in urea and creatinine levels. This confirms that waste products from your pet’s metabolism are accumulating in its bloodstream; these are responsible for anorexia, vomiting and overall feeling unwell. Sometimes, calcium levels are raised and cause calcifications in the kidneys and bladder. Phosphorus is often increased and needs to be controlled otherwise it can have deleterious effects on the kidneys. Low potassium could cause muscular weakness.

In chronic cases, anemia could set in. The kidneys produce erythropoietin which is essential to hemoglobin formation and this will prevent red blood cells production. When anemia is present, we will often hear a heart murmur.

A urine analysis is a very important part of our database. This will enable us to measure urine specific gravity (concentration of urine) and confirm renal insufficiency. We might also want to culture urine to rule out/in a urinary tract infection and to measure a urine protein/creatinine ratio.

It’s very important to measure blood pressure because 10-15% of pets will have hypertension at the initial diagnosis and another 15% will acquire it during the course of the disease.

Additional tests such as radiographs and ultrasound may be recommended.

Treatment

Even though there is no specific treatment to treat the kidney condition itself, there are treatments to address the different problems as they appear. These will help to slow down disease progression, alleviate symptoms and prolong life. With the different tests done, we will try to stage the disease and determine an overall treatment plan.

Renal diets are ideal; they contain reduced amounts of phosphorus, sodium and proteins and have a high biological value. They are high in omega-3s which have a beneficial anti-inflammatory effect. Those diets are best suited to prevent uremic crisis and will prolong life for these pets. Because they can be less appetizing than their previous diet, we recommend that you introduce the new diet over several weeks. If your cat refuses the renal diet but will voluntarily eat another diet, we will have to accept that. A canned diet is always a preferred choice because it contains a lot of water and this will help with chronic dehydration. If your pet refuses a canned diet then we recommend other ways to increase drinking such as a water fountain, having many drinking stations available in the house, using clear glass bowls, adding ice cubes to the water.

It is possible that the lower amounts of phosphorus in the renal diet won’t be enough to maintain the desired blood levels; we would then reach for a medication that binds phosphorus in the bowel before it is absorbed.
Appetite stimulants are helpful for dogs that don’t eat enough to maintain their weight.

Recently, we have a product called Azodyl that has been shown to be helpful to lower uremia in chronic renal insufficiency. It’s basically a nutritional supplement containing good bacteria that help to reduce toxins at the bowel level. It is recommended at the first signs of kidney disease.

To try to control nausea and vomiting, we might prescribe medication for this.

Since affected kidneys cannot retain water, your dog will urinate a lot. To balance this, it should drink more to compensate the loss but as they often eat less and vomit, it’s often not enough and your cat can become dehydrated.

Dehydration reduces perfusion to the kidneys and therefore can worsen kidney function dramatically. The best way to treat a cat having a uremic crisis is by keeping in the hospital on intravenous fluids. After this, we will most likely recommend subcutaneous fluids at home; these are fluids injected by the owner at home usually every day.

A potassium supplement is often given orally twice a day. If owners cannot do this, it can be added to the subcutaneous fluids.

Kidney disease can also bring on hyperparathyroidism. This condition affects calcium metabolism and is characterized by an elevation of the parathyroid hormone (PTH). This rise is a consequence of phosphorus retention and a drop in the renal production of calcitriol. Oral administration of calcitriol will cause a decrease in PTH. Even though controlled studies don’t prove this at this point in time, use of calcitriol in these cats suggests that pets would improve the condition and prolong their life.

If the protein-creatinine ratio is increased, it means there is a loss of proteins in the urine and we would recommend benazepril which will reduce blood pressure and increase blood flow to the kidneys.

If your cat has anemia from the renal disease, it is possible togive injections of erythropoietin at home. Usually, we don’t start giving these until the hematocrit is lower than 20 and when the cat has symptoms from the anemia ( increased heart rate, loss of appetite).We have to bear in mind, that some cats can start producing antibodies against their own red blood cells causing anemia.

Hypertension is must be treated because it can retinal detachment and worsen renal function.
Bear in mind that your pet will need to be rechecked periodically and that blood tests are necessary to evaluate response to treatment.