Chronic kidney disease is one of the most common diseases in older cats and dogs. However, it can occur in animals of any age. There are multiple causes of kidney disease and one of the very frustrating things about this disease is that often by the time it is identified, the cause itself is no longer present and is no longer treatable. And by the time there are obvious abnormalities in kidney blood values, which is a common mode of kidney disease detection, you have marked kidney disease.
The best method of early detection is a urinalysis. But usually animals with early renal disease are not showing any signs of illness, or if they are, the signs are minimal. So, unless it’s part of a routine wellness check with astute techs and vets, the disease is often missed.
Kidney function 101
To understand a little about kidney disease, let’s discuss some of the many functions of the kidney. The kidney is one of the most amazing organs in the body and has numerous critical functions. It filters around 20 percent of the body’s blood, regulates body water and electrolyte balance, and helps regulate arterial pressure and acid base balance. It also regulates the excretion of calcium and the production of the active form of vitamin D. It plays a key role in the metabolism of some important body minerals and produces almost all of a special substance called erythropoietin, which stimulates the production of red blood cells in the bone marrow. In addition to all this, the kidney is responsible for getting rid of metabolic waste products and chemicals through excretion in the urine. If this vital organ is not functioning as it should, there are lots of systemic consequences.
The most common signs that an animal may be experiencing kidney dysfunction are increased thirst and urination. In later stages of the disease, gastrointestinal signs such as bad breath, vomiting, poor appetite and diarrhea may appear. There may also be a gradual decline in body condition with weight loss and poor hair coat. Some animals show no signs at all, and their disease is picked up, as stated above, during routine physical examination and screening tests of blood and urine.
Kidney disease 101
A large number of medical problems can cause kidney disease in dogs and cats. The most common causes of kidney disease in dogs are toxins and infectious diseases. Commonly encountered kidney toxins in dogs are antifreeze (ethylene glycol), vitamin D, and grapes and raisins. Cholecalciferol (vitamin D) is a common ingredient in rodent poison, vitamin supplements and even psoriasis creams. (Toxic exposure is more common in dogs than cats.) When consumed, it is metabolized by the body into calcitriol, which changes renal absorption and resorption of calcium. The result is extremely high blood calcium and phosphorous levels that severely damage the kidneys. If animals are exposed to vitamin D, treatment needs to be prompt to ensure a good prognosis.
The most common infectious diseases causing kidney disease in dogs are pyelonephritis, leptospirosis and Lyme disease. So, it’s important to be aware of these precursors and follow up with a visit to your vet as soon as possible should you suspect your animal may have come into contact with, or been afflicted by, any of the above.
Kidney disease is typically irreversible. Animals with kidney disease can be stable for long periods with good treatment, but ultimately the disease will progress. Cats with chronic kidney disease tend to tolerate the disease and live much longer than dogs. Treatment has multiple goals, one of which is keeping animals hydrated. One good strategy is providing flavored water; you can try low sodium chicken or beef broth. Some animals will tolerate subcutaneous fluids (fluids given under the skin). There are also special prescription diets formulated for animals with kidney disease that have demonstrated some clinical benefit, and studies have shown benefit from supplementation with essential fatty acids.
As veterinarians, we also pay attention to blood electrolytes in our kidney disease patients. Some animals need special drugs to bind phosphorus, and some need potassium supplementation. Depending on the degree of kidney disease, some animals leak protein into their urine and require medication to help with this. Often, our kidney patients develop high blood pressure and anemia. Animals with kidney disease need ongoing regular visits with their veterinarians so we can fine-tune and individualize therapy.
The good news is that there are some exciting newer treatment options. In cats, renal transplant has worked quite successfully. In cats and dogs, continuous renal replacement therapy has been used in universities and teaching hospitals. In a form of dialysis, the patient's blood is passed through filtration tubing into a machine where waste products and water are removed. From there, the patient's blood is taken into the Continuous Renal Replacement Therapy (CRRT) unit. The uremic toxins are removed and the electrolytes are normalized, and then the blood is returned to the patient.
Though animals with kidney disease will eventually succumb to their disease, they can live longer and happier lives with new treatment options.