A longitudinal study on the acceptance and effects of a therapeutic renal food in pet dogs with IRIS‐Stage 1 chronic kidney disease

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Chronic kidney disease (CKD) is an irreversible disease, with progressive loss of renal function eventually leading to uremic crisis and death (Finco et al., 1999; Polzin, 2011). Chronic kidney disease is characterized by structural or functional abnormalities of the kidney(s) that have been present for at least 3 months or longer (Polzin, 2011). Prevalence estimates for CKD in dogs have varied from 0.05% to 3.74%, although a more recent estimate of true prevalence among dogs attending UK primary care veterinary practices was around 0.4% (O'Neill et al., 2013). Prevalence may be much higher in areas endemic for vector‐borne diseases such as leishmaniasis (Cortadellas, del Palacio, Bayon, Albert, & Talavera, 2006). Data from IDEXX Laboratories, Inc in the USA, from approximately 3 million dogs with SDMA concentrations measured since July 2015, show that the prevalence of CKD increases with age (Figure 1). Approximately, 7%–10% of dogs 8–10 years of age have elevated SDMA alone, or elevated SDMA and creatinine. Complications of CKD include metabolic disorders, especially hyperphosphatemia, metabolic acidosis, and hyper‐ and hypokalemia, as well as dehydration, anaemia, proteinuria, and arterial hypertension (Polzin, 2011). Chronic kidney disease occurs mostly in older dogs, and cardiac disease is a frequent comorbid disorder (O'Neill et al., 2013).
Dogs with CKD are staged according to guidelines developed by the International Renal Interest Society (IRIS) and accepted by the American and European Societies of Veterinary Nephrology and Urology (Polzin, 2013). The IRIS stages range from mild (IRIS‐Stage 1) to the most severe (IRIS‐Stage 4), and are based upon serum creatinine (Cr) concentrations, the magnitude of proteinuria as measured by the urine protein:creatinine (UPC) ratio, and blood pressure. Staging guidelines are helpful for making diagnostic, prognostic, and therapeutic recommendations for CKD.
Currently, nutritional management of CKD is recommended when serum Cr exceeds 1.4 mg/dl in dogs with IRIS‐Stage 2 CKD, or when dogs with IRIS‐Stage 1 CKD have a UPC ratio >0.5 (http://www.iris-kidney.com/pdf/treatment-recommendation-dogs.pdf). Dietary interventions that might benefit renal function in non‐azotemic dogs with moderately reduced glomerular filtration rate (GFR), yet persistently impaired urine concentrating ability or persistent proteinuria, e.g., IRIS‐Stage 1 CKD, have not been well studied. Typical therapeutic renal foods have reduced protein, phosphorus, and sodium content, increased caloric density, increased buffering capacity, and increased soluble fibre, B‐complex vitamins, antioxidants, and omega‐3 fatty acids (Polzin, 2013). The goals of nutritional therapy are to slow progressive loss of kidney function, reduce clinical and biochemical consequences of CKD, and maintain adequate nutrition (Brown, Elliott, Francey, Polzin, & Vaden, 2013; Polzin, 2013).
In a double‐blinded clinical trial, dogs with spontaneous CKD fed therapeutic renal food experienced a median of 615 days before uraemic crises developed vs. 252 days in dogs fed maintenance food (twice as long) (Jacob et al., 2002). The dogs fed renal food lived at least 13 months longer than the dogs fed maintenance food (Jacob et al., 2002). It was also noted that feeding renal food to dogs with a lesser degree of azotemia (serum Cr concentration 2.0–3.1 mg/dl) delayed the onset of uremic crises by approximately 5 months (Jacob et al., 2002). It is unknown if the renal function is stabilized (based on serum renal biomarker concentrations) in non‐azotemic dogs with IRIS‐Stage 1 CKD with early dietary intervention.
The purpose of this study was to assess the acceptance of a therapeutic renal food and its influence on the renal function biomarkers when fed to client‐owned dogs with IRIS‐Stage 1 CKD over a 12‐month period. Prescription Diet® k/d® (Hill's Pet Nutrition, Inc) contains protein and phosphorus concentrations that meet the Nutrient Requirements of Dogs (NRC 2006) recommended allowances.
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