Your cat’s kidneys do many important things, including manage fluid balance, blood pressure, stimulate the production of red blood cells, and remove waste from the blood. Kidney compromise in your cat can therefore affect hydration status, blood pressure, energy levels and appetite.
Causes of Kidney Compromise
Kidney compromise falls into 3 broad categories: chronic kidney disease, inherited kidney diseases, and acute kidney disease. The most common type of kidney compromise is chronic kidney disease (CKD). CKD begins early in life and progresses to renal failure with age. Early diagnosis of chronic kidney disease and good care can boost both the quality and length of your pet’s life.
However, older cats aren’t the only ones at risk. Kittens can be born with kidney diseases. Congenital (existing at birth), inherited or genetic kidney diseases are processes that affect the development and growth of the kidneys before or shortly after birth. Most patients are less than 5 years of age at the time of diagnosis. Some renal diseases in this category include: complete absence of one or both kidneys (renal agenesis); abnormal kidney development (renal dysplasia); polycystic kidney disease, characterized by formation of multiple, variable-sized cysts throughout the kidney tissue; nephroblastoma (a congenital kidney tumor).
Acute renal failure is a set of conditions that are marked by a sudden decline in renal function, usually as a result of a toxic, infectious, or vascular insult. The kidneys receive approximately 20-25% of blood pumped from the heart; therefore they are particularly susceptible to various types of vascular injury. Insufficient blood flow to the kidneys as with dehydration, and toxic and infectious diseases can cause acute renal failure. Plants in the lily family, antifreeze, Ibuprofen, Tylenol and other drugs can have a significant negative effect on kidney function. Obstruction of urine flow by kidney stones or urethral obstruction by feline idiopathic cystitis can result in acute kidney failure.
Symptoms of Kidney Compromise:
Lack of appetite
Lack of energy
After discussing the background history of symptoms and any possible incidents that might have led to this condition, your veterinarian will perform a thorough physical exam on your cat. Based on the history and physical exam, your veterinarian will most likely order a blood chemical profile, a complete blood cell count, an electrolyte panel, and a urinalysis. Abdominal x-rays, and/or abdominal ultrasound may be performed to identify and characterize the kidney disease your cat is suffering from. If appropriate, direct genetic tests are available for detection of specific genetic mutations, such as familial polycystic renal disease in Persian and Persian-derived breeds of cats.
Risk Factors Associated with the Development of Chronic Kidney Disease
Chronic Kidney Disease is prevalent in up to 35% of geriatric cats1. Some risk factors for CKD in cats include increasing age, high blood pressure, thin body condition and/or weight loss, prior periodontal disease, prior anesthetic episodes, cystitis (inflammation of the bladder), and dehydration in the preceding year. Longer survival time has been documented when the diagnosis is made early on in the disease2.
Early Diagnosis of Chronic Kidney Disease
Early detection of CKD is important in successful management of the disease in slowing its progression and improving the quality of life of the affected patient. Laboratory and clinical findings used to diagnose CKD include increased serum creatinine (sCr), decreased urine specific gravity, weight loss, halitosis, and decreased kidney size. Unfortunately, these findings remain normal until about 75% of the kidney function is lost. Therefore, an earlier and more accurate biomarker of kidney function is needed. Recently, researchers have found a protein that is eliminated by the kidneys called symmetric dimethylarginine (SDMA). This protein increased about 14-17 months earlier than sCr increased above the normal reference range. These researchers found that increased SDMA was effective in confirming CKD in 86% of cases. Therefore, the SDMA biomarker would be very useful in helping owners and veterinarians become more proactive in detecting and managing early CKD2, 3.
Treating a kidney compromised cat
Five steps are involved in treating kidney compromise in cats
Step 1: Rehydration
The cornerstone of therapy for kidney compromise is rehydration and maintenance of a hydrated state. Fluid therapy for rehydration may consist of intravenous (IV) fluids, but subcutaneous fluid therapy may be adequate.
Isotonic fluid solutions are used to rehydrate and provide maintenance therapy to help prevent increases in phosphorus and decreases in potassium and balance electrolytes. Intermittent subcutaneous fluid therapy is often prescribed for patients with chronic kidney disease and can be administered as an outpatient or at home, depending on the severity and stability of the disease.
Step 2: Diuresis
Diuresis is defined as the physiological process by which urine production in the kidneys is increased as part of the body’s maintenance of fluid balance. This is accomplished by the administration of fluids for patients with kidney disease. Newly diagnosed patients may need to receive IV fluid therapy to correct dehydration, improve kidney perfusion, and promote diuresis. Patients in kidney failure often require more fluids than the daily maintenance rate. Many toxins are excreted, either fully or partially, via the kidneys, so fluid therapy along with other treatments is used to hasten toxin elimination. In some cases, such as with non-steroidal anti-inflammatory drug (NSAID, i.e. Tylenol, Ibuprofen, and aspirin) toxicity and lily ingestion (cats), IV fluid therapy is recommended for 48 to 72 hours to help perfuse the kidneys and prevent acute kidney injury. The rate of administration should be 2 to 2.5 times higher than a typical maintenance rate to assure sufficient diuresis, as long as the patient’s clinical status does not contraindicate a high fluid rate.
Step 3: Diet – Protein and restriction of dietary phosphorus
Chronic kidney disease causes increases in blood urea nitrogen (BUN) and creatinine. One of the by-products produced when the body breaks down protein in food is BUN. When the kidneys are compromised, animals can’t remove BUN efficiently, and your pet feels nauseous and has a poor appetite. This can lead to muscle wasting in senior cats with CKD4. The dietary treatment of CKD in cats typically includes less protein and less phosphorus than diets designed for normal animals. These diets also often contain increased amounts of fish oil and moderate amounts of sodium. Phosphorus restriction has been shown to slow the progression of CKD and adding fish oil has been shown to slow the development of pathological changes in the kidney, but the value of protein restriction in slowing progression of disease remains uncertain5, 6 Nevertheless, studies have shown that survival is prolonged more than twofold in animals with CKD, when animals are fed commercial “kidney” diets with less protein and phosphorus compared when cats are fed normal maintenance diets7, 8, 9. Sometimes a diet change alone will help your pet feel better. Several low-protein, low phosphorus diets are available through veterinarians to slow the progression of kidney disease. To help prevent muscle wasting in conjunction with chronic kidney disease, consider giving egg whites to your pet. This is the highest quality protein available and all the phosphorus is in the yolk! Along with anti-nausea medication, appetite stimulants, and probiotics (discussed below) you can significantly improve your cats’ appetite while slowing the progression of CKD.
When a significant amount of kidney function is lost and the kidneys are unable to get rid of excess phosphorus, it may be necessary prevent the absorption of phosphorus from the food and a phosphate binder medication may be indicated. Phosphate binders—in liquid, powder, or tablet form—binds to phosphorus in food and prevents it from being absorbed into your pet’s bloodstream. Phosphate binders must be given with meals, because the medication can’t do its job without food. If you change the frequency of feeding, talk to your veterinarian about changing the phosphate binder dose so you can give it with each meal.
Step 4: Additional therapies for anemia, nausea, anorexia.
Anemia (low red blood cell count) is common in pets with chronic kidney failure. The kidneys make a hormone called erythropoietin that tells the bone marrow to make new red blood cells to replace older cells as the older cells are removed. When kidneys fail, they stop making adequate amounts of this hormone. The anemia develops slowly, giving the pet time to adapt. When the anemia is moderate to severe, your pet may appear tired or unwilling to eat. Human erythropoietin replacement shots and/or blood transfusions are available to treat anemia. Vitamins with iron may be helpful.
Appetite stimulants, stomach acid reducers and anti-nausea and vomiting (occasionally with blood) drugs may be prescribed. Famotidine (Pepcid AC) or other drugs that reduce gastric acidity reduce stomach ulcers and improve appetite. Mirtazapine (Remeron) is effective in many cats to stimulate appetite. Maropitant (Cerenia) is an effective anti-vomiting, anti-nausea medication that is helpful in the treatment of inappetence in cats with renal failure. Often potassium supplements either given in fluids or orally are needed. Your veterinarian can answer questions about the best medications and dosing schedules for your pet.
Probiotics (Azodyl, Kibow Biotics) metabolize toxins in the large intestine, sparing the compromised kidneys of this burden. Toxins normally move between the blood and the gastrointestinal tract. As the kidney’s function slows down, wastes build up in the blood (azotemia) and diffuse into the intestinal fluid by a natural physiological process. While probiotics won’t cure renal disease, it can reduce azotemia, slowing the progression of the disease by reducing nausea, inappetance and weight loss.
-Written by Dr. Joel Stone
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Hall JA, Yerramilli M, et al. Comparison of serum concentrations of symmetric dimethylarginine and creatine as kidney function biomarkers in cats with chronic kidney disease. J Vet Intern Med. November 2014: 28(6): 1676-83.
Freeman LM, Cachexia and sarcopenia: emerging syndromes of importance in dogs and cats. J Vet Intern Med. 2012 Jan-Feb: 26(1): 3-17.
Finco, DR; Brown, SA, et al. Protein and calorie effects on progression of induced chronic renal failure in cats. J Vet Research Vol 59, No 5. May 1998.
Finco DR, Brown SA, Crowell WA et al. (1994) Effects of aging and dietary protein intake on uninephrectomized geriatric dogs. Am J Vet Res 55, 1282-1290
Ross SJ, Osborne CA, Kirk CA, et. al. Clinical evaluation of dietary modification for treatment of spontaneous chronic kidney disease in cats. J Am Vet Med Assoc 2006; 229:949-947
Plantinga EA, Everts H, Kastelein AM, et. al. Retrospective study of the survival of cats with acquired chronic renal insufficiency offered different commercial diets. Vet Rec 2005; 157: 185-187
Elliott J, Rawlings JM, Markwell PJ, et al. Survival of cats with naturally occurring chronic renal failure: effect of dietary management. J Small Anim Pract 2000; 41:235-242
About the Author
Joel D. Stone, DVM, Ph.D. – Joel is a graduate of Colorado State University College of Veterinary Medicine, and received a Ph.D. from the University of California, Davis in Comparative Pathology. Following his veterinary medical training, Dr. Stone has worked in clinical practice, pharmaceutical companies and universities. Currently, Dr. Stone works at the All Cat Clinic and Precious Cat in Englewood Colorado, splitting his time between clinical practice, research and writing about feline health topics.