VetCare renal dog food

Meet Dr Marvin Firth MRCVS, DipACVP, MRSB

I have been a vet for over 16 years, having graduated with honours and distinction in veterinary science. Since qualifying as a vet, I have worked with a wide range of species across various countries and throughout the UK.

I have been fortunate to further my studies at Cambridge, Surrey University and the Royal Veterinary College. I have also undertaken work at both Cornell and Utrecht universities in the US and Holland. These varied experiences have enabled me to encounter a massive spectrum of cases relating to our pets and appreciate how preventative health care plays a major role in their longevity and quality of life.

Attaining international specialist status in veterinary pathology has been a pinnacle of my career. This role allows me to support general practitioners and other specialists in the diagnosis and potential treatment of their patients. It is immensely rewarding to provide this level of support within the veterinary community.

I am acutely aware of the human-animal bond, having had my own pets throughout my life, including my current dog, Rye, who constantly reminds me of the deep connection we share with our animals. Whilst I work as a specialist, I continue to see patients in the home every week. This keeps me grounded in the real nature of pets as members of the family and the essential role of a veterinary surgeon as a trusted source of advice and support.

I feel privileged to help both my patients and their owners achieve the best health outcomes. I strongly believe that nutrition is a strong daily contributor to their overall vitality and helps them thrive.

How can a special diet help a dog with renal issues?

Acute kidney injury (AKI) (e.g. from ingesting pesticides) can sometimes be reversible if it’s diagnosed at its earliest stage and treated immediately, but in cases of chronic renal insufficiency, improvement is only rarely possible, and the therapeutic aim is to reduce the rate of demise of function of the kidneys.
Clinical signs may not become evident until there is around 70-85% loss of functional capacity, by which time the damage is irreversible. Therefore, the aim is to stabilise kidney function and slow further progression of the disease. Special veterinary renal diets can help to achieve this since they are specially formulated to lighten the workload of the ailing kidneys, as well as address secondary metabolic changes.

Why do renal veterinary diets restrict protein, phosphorous and sodium for dogs with renal conditions?

 PROTEIN 

When the kidneys are not working properly, the waste products of protein metabolism - ammonia, urea, uric acid and creatinine – (which would normally be efficiently excreted via the urine) can build up to toxic levels in the blood. Reducing the protein intake may reduce the amount of waste. As the kidneys also filter useful substances back into the blood, this can reduce the amount of protein itself from entering them, further lessening their load.
Another consideration is that protein-rich ingredients such as meat and fish are generally rich in phosphorous (which requires restriction too), and promote a more acidic urine (the urine of dogs with renal disease is often already too acidic (low pH).
However, protein should only be moderately restricted because an insufficient supply results in protein malnutrition and loss of lean body mass, which reduces the dog’s strength and immunity. Furthermore, protein metabolism is less efficient in senior dogs, and they therefore need enough to maintain their reserves and maximise renewal and replacement. There have been many studies regarding protein restriction in the progression of chronic kidney disease in dogs, but further investigation is still required [Cline. M, 2015].
Protein restriction is however recommended for dogs with proteinuria (protein in the urine) secondary to glomerular disease (a type of kidney disease affecting the glomeruli which filter plasma) [CGN IRIS, 2013]. It is also beneficial for dogs with hereditary nephritis, as research has shown that this reduces structural damage to the glomeruli and delays the progression of renal failure [Valli et al, 1991].
At present, the degree of protein reduction is generally dependent on the individual’s diagnostic test results and symptoms, and it is also relative to the protein intake provided by the original diet. It is, however, undebatable that the protein eaten by a dog with renal insufficiency is highly digestible and bioavailable, meeting all amino acid requirements. Poor quality proteins give the kidneys a lot of work for limited, if any, nutritional value and therefore foods comprised mainly of indigestible protein (e.g. rawhide) should not be fed.

PHOSPHOROUS

Phosphorous restriction is extremely important because it can slow the progression of renal disease. When filtration is compromised, there are greater circulating levels of phosphorous in the blood. This can then cause a complex endocrine condition called renal secondary hyperparathyroidism and calcitriol (an active form of vitamin D normally made in the kidney) deficiency. Resultant complications include soft tissue mineralisation and fibrous osteodystrophy.

SODIUM

In addition to filtration and waste excretion, the kidneys are also involved in the maintenance of the body’s salt and fluid concentrations which contribute to control blood pressure. Although high sodium diets can increase blood pressure, which may contribute to the progression of renal disease, there is currently no evidence to support that reducing sodium can decrease hypertension in dogs. However, mild sodium restriction is a typical feature of renal diets since it helps avoid the accumulation of high levels when sodium excretion by the diseased kidneys is less efficient [Fascetti & Delaney, 2012]. Sodium should not be suddenly and dramatically restricted since this can cause dehydration, and the ailing kidneys also need time to adjust to a different level.