Feline Chronic Kidney Disease (CKD) and Its Nutritional Management
Feline, Chronic kidney disease (CKD) also known as chronic renal failure (CRF), chronic renal insufficiency. There are some specific degenerative renal diseases, infectious causes and neoplastic renal disease that may lead to renal failure in cats. Chronic renal failure (CRF), a common illness that affects companion animals of all ages but is more prevalent in old (geriatric) age cats. One of three cats in age above 10 yrs have CKD and is a frequent clinical finding, with increasing prevalence as cat’s age; it affects perhaps one-third of our geriatric feline patients (Polzin et al. 1992). It is the main cause of mortality in older cats and is becoming increasingly common. Chronic kidney disease significantly affects the quality of life of both the patients and their owners. The recent advances in the nutrition of companion animals have resulted in a longer possible life-span for cats and an improvement in their quality of life. The importance of the diet in resolving some pathologies lead to the conclusion that correct nutrition is an important tool in disease prevention and a valid aid of therapeutic protocol.
Thus, knowledge of the interaction between the nutritional components of the dietary ration and the physio-pathological processes of the various systems in the organism provides a way to develop new strategies of intervention and control the clinical management of the patient. This type of intervention is particularly applied in veterinary geriatric nutrition because of the constant increase in the number of animals belonging to this age range and because of increasing scientific knowledge about the necessity to adapt nutrition according to the different requirements of different life stages for dogs and cats.
The most common symptoms of the kidney disease in felines include polydypsia, polyuria, selective anorexia, weight loss and inappropriate urination. Other signs include poor body condition, bad breath (halitosis), depression, gingivitis and oral ulceration (Harte et al. 1994). Subtle weight loss including reduced renal size, changes in renal consistency, renal irregularity or disparity in renal sizes, stomatitis, and constipation are some of the physical ailments related to CKD. Retinal examination may reveal hemorrhages or retinal detachment secondary to renal-associated systemic hypertension. Renal failure begins with loss of functioning nephrons, atrophy and fibrosis of glomeruli, renal tubules and peritubular tissues. The functional changes include decrease in renal blood flow, decreased glomerular filtration rate and a reduced capacity to concentrate urine. In the advanced stages of CKD, the high accumulation of nitrogen waste products has an irritant effect on the mucous membranes. The cat suffers from nausea and vomiting and tends to lose its appetite. If this situation persists for a while, the animal undergoes major weight loss and its life expectancy is shortened (Polzin et al. 1995).
Terms related to Kidney disease
Some of the clinical terms related to kidney disease includes, Pollakiuria: is increased frequency of urination, usually with a small volume in each urination. Stranguria: painful urination and dysuria: difficult urination, are often used inter changeably. Polydipsia: increased water consumption, Polyuria: frequent urination. Azotemia: is a condition characterized by abnormal levels of nitrogen-containing compounds, such as urea, creatinine, various body waste compounds, and other nitrogen-rich compounds in the blood. Uremia: Excess nitrogenous waste products in the blood and their toxic effects; a toxic condition resulting from kidney disease in which there is retention in the bloodstream of waste products normally excreted in the urine also called as azotemia.
CKD: How to Diagnose
Clinical history is one of the main things to arrive at the symptomatic diagnosis of the disease. Chronic kidney disease in cats is characterized by an irreversible and progressive loss of kidney function and the development of clinical signs that reflect the kidney’s decreasing ability to perform normal regulatory and excretory functions. The diagnosis in mainly based on history, physical and laboratory examinations etc. A history of signs as polyuria, polydipsia, weight loss, selective appetite over several months is strong evidence for CKD. Physical examination showing poor nutritional status, poor haircoat and small kidneys etc. are important indicator of kidney disease. As geriatric animals are more prone to CKD, routine laboratory screening of old age cats is recommended as a standard of practice for diagnosis of CKD. All middle-aged to older cats should receive at least once yearly historical assessment, thorough physical examination, and appropriate laboratory screening for CKD. Laboratory test includes Blood urea nitrogen, serum creatinine, sodium, potassium, phosphorus, chloride, calcium, albumin and total protein to establish the diagnosis and identify renal complications, complete blood count including urine culture to rule-out urinary tract infection.
Nutritional Management of the CKD
Nutrition plays important role in health and disease of human as well as animals. Nutritional therapy has been the mainstay of medical management of feline chronic kidney disease for decades. In the management of cats with CRF, the amount eaten is as important as what is eaten. Cats with CRF often have reduced appetites, and special diets formulated for this condition have variable palatability. Changes in body weight should be carefully documented by the veterinarian. An accurate log of food intake should be maintained by the owner and reviewed by the veterinarian at each visit. The composition of the diet is important for maintaining homeostasis in cats suffering from chornic kidney disease (CKD) and helps to improve the animal’s quality of life. Dietary protein and other nutrients are known to influence clinical signs of uremia, electrolyte and mineral balance, as well as the overall nutritional status of renal-failure patients. Renewed interest in dietary management of renal failure has been stimulated by the observation that modification of diet may reduce the rate of progression of chronic renal failure (Polzin et al. 1991).
Recommended therapeutic measures include maintaining normal calorie intake, restoration and maintenance of body fluid balance, feeding a reduced protein, reduced phosphate diet and supportive symptomatic therapy that aim to minimize disruptions in fluid, acid-base, electrolyte and nutritional status. The aim of treatment is to minimize the clinical and pathological consequences of renal failure. Reduced kidney function may adversely affect phosphate homeostasis hence; dietary therapy intends to normalize serum phosphorus concentration.
Vomiting and anorexia are common in cats with CKD and can often result in decreased caloric intake. So, it’s important to maintain adequate energy intake to keep them active. An ideal caloric intake is one that will sustain a normal activity level and normal body weight. The animal’s energy intake should be adapted to its needs and therefore its weight and body condition score should be assessed regularly. Inadequate intake can be loosely defined as <50 kcal/kg/day with weight loss or poor body condition. Cats generally need between 50 and 60 kcal/kg/day. Since lipids provide around twice as much energy as carbohydrates, per gram consumed, they increase the food’s energy density, which makes it possible to decrease the volume of the ration and thus reduce the risks of nausea and vomiting. Food and thus calorie intake may be increased in various ways, which includes making all dietary changes gradually, offering different forms of the diet (e.g., dry versus moist formulations), warming the food, providing fresh food daily, frequently offering small amounts of food, often by hand, may be helpful in some patients. The addition of a small amount of palatability enhancing agent, such as fat, also adds to caloric intake (Finco et al. 1998).
Mostly geriatric cats due to age shows reduced thirst response to dehydration, hence consumes less water compared to their younger counterparts. Cats suffered from CKD generally are dehydrated which contribute them more prone to azotemia. Moist and semisolid food with added water can take care of cats partial water requirement. Efforts to increase voluntary water consumption include providing clean, fresh water at all times, feeding a canned food diet (with added water if possible), low sodium, bottled juice. Cats that like to drink from running water sources may drink more enthusiastically from a recirculating water fountain than a water bowl. Adequate fresh water intake must be assured (Buranakarl et al. 2004).
Protein and phosphorus intake
The restriction of dietary protein and phosphorus are important aspects of dietary management of advanced renal insufficiency. As cats dietary protein requirements are more as compared to dogs, care has to be taken while introducing low protein diet. Generally low protein diets are less palatable; hence, these diets should be used judicially while feeding cats suffered from CKD. Restriction of phosphate intake, using restricted phosphate diets and intestinal phosphate binding agents, is recommended as the mainstay of therapy for CKD in veterinary medicine. The restriction of phosphorus helps in controlling hyperparathyroidism which is caused due to imbalance in calcium and phosphorus (Barber and others 1999). In experimentally induced renal failure in cats, phosphate restriction was shown to reduce the mineralization and severity of lesions which developed in remnant kidneys. Management with a diet providing 15.1 g protein and 0.23 g phosphorus/MJ metabolizable energy (ME), compared with a diet providing 23.6 g protein and 0.48 g phosphorus/MJ ME, appeared to result in slowing of the rate of clinical deterioration in cats (Elliott et al. 2000).
Finally, feeding a veterinary clinical diet (with intestinal phosphate binders where necessary) specifically formulated for feline renal failure was associated with a highly significant beneficial effect on survival of cats presenting with naturally occurring stable CKD. Provision should also be made to assure adequate intake of water-soluble vitamins, which may be depleted in polyuric animals. However, care should be taken to avoid excessive supplementation as this will alter the nutrient balance of the diet, particularly if certain nutrients have been restricted. Increasing the activity of the animal may enhance its appetite. Other therapies may indirectly enhance activity level, such as specific therapy for anemia, electrolyte abnormalities, or uremia etc.
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Finco DR, Brown SA, Brown CA, Cromwell WA, Sunvold GD and Cooper TL. 1998. Protein and calorie effects on progression of induced chronic renal failure in cats. American Journal Veterinary Research. 59:575-582.
Polzin DJ, Osborne CA and Adams LG. 1991. Effect of modified protein diets in dogs and cats with chronic renal failure: current status. Journal of Nutrition. 121: S140-S144
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Polzin DJ, Osborne CA, Bartges JW, James KM and Churchill JA. 1995. Chronic renal failure. In: Ettinger SJ, Feldman EC, eds. Textbook of Veterinary Internal Medicine. Philadelphia: WB Saunders, pp. 1734-1760.