Nutritional management of chronic renal failure in dogs

Renal disease is a frequent cause of illness and death in dogs, affecting approximately 1% of all dogs and up to 10% of canine patients over ten years of age. The hallmark of chronic renal failure (CRF) is a gradual decline in the glomerular filtration rate (GFR).

Based on serum creatinine concentrations, the IRIS¹ has divided canine CRF into four phases:

• Stage 1: Serum creatinine <125 µmol/l – Non-azotaemic – Some other abnormality present (e.g., inadequate concentrating ability, sub-clinical renal damage).
• Stage 2: Serum creatinine 125-179 µmol/l – Mild renal azotaemia – Clinical signs usually mild or absent.
• Stage 3: Serum creatinine 180-439 µmol/l – Moderate renal azotaemia – Many clinical signs may be present.
• Stage 4: Serum creatinine >440 µmol/l – Severe renal azotaemia – Many extra-renal clinical signs present.

Dietary intervention has a pivotal role to play in the management of this disease, with the major aims of dietary therapy being to slow progression of disease, manage complications associated with CRF and alleviate clinical signs of disease, whilst maintaining the dog's well-being.

SLOWING DISEASE PROGRESSION

• Phosphorus excretion is reduced in CRF, causing hyperparathyroidism and hyperphosphataemia. This contributes to nephrocalcinosis and progression of disease. Dietary restriction of phosphorus is vital in preserving renal structure and function and slowing the progression of renal damage.
• The survival of dogs with CRF is significantly enhanced by restricted phosphorus diets, and IRIS recommend phosphate restriction starting at Stage 2 disease, with different realistic target serum concentrations¹.
• While phosphate restriction is the major target to preserve renal function, there is evidence in dogs that supplementation with omega-3 fatty acids may help reduce glomerular hypertension, increase renal blood flow and minimise renal inflammation thereby slowing progression of the disease².
• Supplementation with omega-3 fatty acids can lower systemic arterial pressure, which could be beneficial in patients with hypertension and CRF.
• There is additional data showing that oxidative stress may be harmful in CRF, may contribute to the progression of canine CRF, and that this effect can may be ameliorated by anti-oxidant supplementation, thus again helping to preserve renal function³.

IMPROVING CLINICAL SIGNS

• The declining GFR in dogs with CRF leads to an accumulation of a wide variety of waste products that contribute to uraemic signs.
• While protein restriction has no proven effect on progression of CRF, moderate reduction of non-essential amino acids will result in decreased production of uraemic toxins.
• Protein levels must be adequate to supply the needs of the CRF patient to avoid catabolism of body proteins and an increased morbidity.
• Addressing the acid:base balance is important as metabolic acidosis is common in CRF and can contribute to signs such as anorexia, lethargy, vomiting, weakness and weight loss.
• Sodium retention and extracellular volume expansion may occur with advanced CRF and may contribute to development of systemic hypertension. Mild sodium restriction may help reduce this risk.
• Increased losses of B vitamins may occur with the diuresis associated with CRF, which may also contribute to clinical disease.

CLINICAL ADVANTAGES WITH USE OF CANINE NF IN DOGS WITH CRF

Canine NF is carefully formulated to provide for the specific needs in canine CRF:

• Restricted phosphate concentrations.
• Controlled levels of high quality protein.
• Added omega-3 fatty acids and anti-oxidants.
• Added potassium citrate to combat acidosis.
• Enhanced levels of B-complex vitamins.
• Moderate sodium restriction.

Additionally, Canine NF has excellent palatability, which is an essential component of dietary therapy as appetite is very frequently compromised in CRF patients.