Chronic Kidney Disease

• The kidneys act to remove waste products from the blood stream, regulate the levels of certain essential minerals (such as potassium and sodium), conserve water, produce urine, produce erythropoietin that stimulates red blood cell production by bone marrow, and modifying vitamin D derived from the diet into its final active form (calcitriol).
• In the kidneys, more than 99 percent of the fluid that is filtered is returned to the blood and less than one percent is excreted.
• Chronic renal, or kidney, failure is an irreversible loss of all the kidney's functions.
• CKD is commonly considered an illness of older dogs and cars, but it can occur in animals of all ages.
• CKD is not reversible.
• CKD may have been present in a pet for months or years before time of diagnosis.
• Although there is no cure for CKD, it can be successfully managed, with nutritional therapy playing an important role in treatment.
• The goals of nutritional management of CKD are to meet the patient's nutrient and energy requirements, as well as to alleviate clinical signs and slow the progression of the disease.
• CKD is progressive and therefore repeated assessment and subsequent changes in your pet's care and diet may be necessary to successfully manage this process.
• Nutritional intervention is a cornerstone in the treatment of patients with CKD. However, a complete nutrition assessment and staging the patient's CKD are indicated before any dietary recommendations are made.
• The International Renal Interest Society (IRIS) recommends nutritional intervention in both cats and dogs at stage two, but a diet change at stage one may be required once a complete assessment of the patient has been performed.
• Step one of IRIS is to diagnose CKD. For stage one or early stage two, this can be done with increased creatinine levels, persistent increased SDMA > 14 ug/dL, abnormal kidney imaging, and persistent renal proteinuria. For late stage two to four, all the previous parameters, increased creatinine and SDMA concentrations, and decreased specific gravity (< 1.030 in dogs and <1.035 in cats) can determine the stage.
• Step two of IRIS is to stage CKD. This is done be seeing matching the pet's laboratory results with certain parameters. The category it falls the most in is the stage it is in.
• Stage one has no azotemia, normal creatinine (less than 1.4 in dogs and 1.6 in cats), an SDMA less than 18, have a UPC ration of nonproteinuric ( less than 0.2) and have a normotensive systolic blood pressure (less than 140).
• Stage two has mild azotemia, normal or mildly elevated creatinine (1.4 to 2.8 in dogs and 1.6 to 2.8 in cats), elevated SDMA (18 to 35 in dogs and 18 to 25 in cats), be borderline proteinuric (0.2 to 0.5 in dogs and 0.2 to 0.4 in cats), and prehypertensive (140 to 159).
• Stage three has moderate azotemia, increased creatinine (2.9 to 5 in dogs and 2.9 to 5 in cats), elevated SDMA (36 to 54 in dogs and 26 to 38 in cats), borderline proteinuric (0.2 to 0.5 in dogs and 0.2 to 0.4 in cats), and hypertensive (160-179).
• Stage four has severe azotemia, elevated creatinine of more than 5, elevated SDMA (more than 54 in dogs and more than 38 in cats), proteinuric (more than 0.5), and severely hypertensive (more than or equal to 180).
• Step three in IRIS is to treat CKD.
• Treatment for stage one CKD includes using nephrotoxic drugs with toxin, correct prerenal and postrenal abnormalities, have fresh water available at all times, monitor trends in creatinine and SDMA to document stability or progression, investigate for and treat underlying disease and complications, treat hypertension if systolic pressure is persistently greater than 160 or there is evidence of organ damage, treat persistent proteinuria with a renal therapeutic diet and meds, keep phosphorous below 4.6, and use a renal therapeutic diet and a phosphate binder.
• Treatment for stage two CKD includes all the approaches for stage one, a renal therapeutic diet, treat hypokalemia in cats, and treat inappetence and nausea if present.
• Treatment for stage three CKD includes all the approaches in stage two, keeping phosphorous below 5.0, treat metabolic acidosis, consider treatment of anemia, treat vomiting, inappetence, and nausea, and increase enteral or subcutaneous fluids may be required to maintain hydration.
• Treatment of stage four CKD includes all the approaches in stage three, keeping phosphorous below 6, and consider a feeding tube for nutritional and hydration support and ease of medicating.
• The nutritional assessment checklist for patients with CKD includes a dietary history, laboratory values, and patient assessment.
• A diet history includes appetite, current diet, evaluation of current protein intake, treats and table foods, foods for medication administration, and supplements.
• Laboratory values for nutritional assessment for CKD includes creatinine, blood urea nitrogen, phosphorus, potassium, albumin, bicarbonate, urine specific gravity, and urine protein to creatinine ratio.
• Patient assessment for the nutrition assessment for CKD should include body weight, body condition score, muscle condition score, and systolic blood pressure.
• Therapeutic kidney diets are used to improve a patient's quality of life by controlling signs of uremia and increasing the lifespan by altering disease progression.
• Double blinded, randomized controlled clinical trials have compared the effectiveness of diets formulated for CKD with adult maintenance diets in dogs and cats. They evaluated the characteristics of therapeutic kidney diets, such as reduced phosphorus, protein, and sodium and the addition of omega 3 fatty acids.
• Cats with spontaneous IRIS stage two and three CKD were fed a therapeutic kidney diet or an adult maintenance diet and were evaluated for 24 months. In the therapeutic diet group, no cats experienced a uremic crisis and no renal related deaths occurred. In the maintenance diet group, 26 percent of cats had uremic crisis and 21.7 percent died of renal related causes.
• Clinic owned cats with spontaneous stable CKD were fed a therapeutic kidney diet or an adult maintenance diet. Those fed a maintenance diet received one because they refused the therapeutic diet or the owners did not want to change. Feeding a therapeutic kidney diet helped reduce plasma phosphate, blood urea nitrogen, and parathyroid hormone concentrations. The median survival time for cate getting a therapeutic kidney diet was 633 days (1.7 years) compared with 264 days (0.7 years) for cats getting the maintenance diet.
• Dogs with spontaneous IRIS stage two or greater CKD were fed a therapeutic diet or adult maintenance diet and evaluated for 24 months. Dogs with the VTD had a median time to uremic crisis of 615 days (1.7 years) and a median time of 594 days (1.6 yrs) before deaths occurred. Those in the maintenance had a median time to uremic crisis of 252 days (0.7 years) and 188 days (0.5 years) before deaths occurred. At the end, only 33 percent of dogs in the VTD group died of renal related cause compared to 65 percent of dogs in the maintenance group.
• Key nutrients that need to be considered when feeding patients with CKD include protein, phosphorus, omega 3 fatty acids, sodium and potassium. Fat, acid base balance, antioxidants, and fiber should also be considered.
• Protein restricted diets are commonly recommended for management of CKD in both dogs and cats in order to reduce nitrogenous wastes and glomerular proteinuria.
• Nitrogenous wastes can contribute to clinical signs associated with azotemia and uremia, polyuria, polydipsia, anemia through gastrointestinal ulceration and blood loss, shorten the life span of red blood cells, and cause platelet dysfunction.
• Reduction of nitrogenous wastes can improve polyuria and polydipsia by reducing solute load to the kidney.
• Protein requirements for adult dogs and cats have been established through use of nitrogenous balance studies, wherein nitrogen intake is equivalent to nitrogen loss.
• AAFCO recommends a minimum crude protein content for adult dogs and cats, taking into account not only the recommendations from the NRC for healthy adults but also changes in protein digestibility that occur during the processing of pet food.
• Nitrogen balance can be achieved on a low protein diet; however, this may be at the expense of lean body mass through the utilization of endogenous.
• A more recent study evaluated the protein requirement of adult cats based on the maintenance of lean body mass. This study was performed in healthy male adult cats, and additional studies are needed to evaluate the protein requirement to maintain lean body mass in dogs and cats with CKD.
• The amount of protein needed to achieve restriction is not clearly defined, although there are categories for low, moderate and high protein diets.