The role of dietetic food in animal kidney disease

The role of dietetic food in animal kidney disease

The diet of domestic carnivoreshas grown considerably over the past two decades. In veterinary medicine for domestic carnivores, dietetic food is opposed to the so-called physiological food which is intended for healthy animals. Dietetic food is a complement to treatment or even full treatment of certain clinical situations, through the establishment of a specific diet adapted to the condition in question.

Chronic renal failure

Chronic kidney disease (CRF) is often detected late when (70% of nephrons are usually already affected). Nutritional support aims to restrict the quantitative intake of phosphorus, which is poorly eliminated by the kidney. An increase in its plasma concentration is thus avoided, and that of calcium is maintained within a physiological range. This prevents the risks of secondary hyperparathyroidism and osteodystrophy of renal origin which would lead to mineralization of soft tissues and excessive mobilization of bone calcium.

The other goal of this nutritional support is to decrease the amount of protein. By reducing the excretion of the products of protein catabolism, this would prevent the overload of still functional nephrons. In addition, the intake of proteins of high biological value will serve to best adjust the protein intake according to the needs of the animal. It will thus allow the limitation of the excretion of the products of protein catabolism.

In addition, in kidney failure, we often have metabolic acidosis. It is therefore necessary to avoid bringing a ration that is too acidic. In general, restricting the amount of protein helps minimize this metabolic acidosis.

Struvite stones

In dogs, struvite stones or phospho-ammonia-magnesian stones are frequently observed. Urinary tract infections are a predisposing factor for the formation of these stones. This is because Staphylococcus and Proteus type germs have ureases responsible for converting urea into ammonia. This phenomenon thus makes the pH more basic and lowers the solubility of phospho-ammonia-magnesian salts, at the origin of the formation of these stones.

In cats, however, the frequency of these stones is rarely associated with a urinary tract infection. These sterile stones are mainly due to a diet too rich in magnesium. This causes a phenomenon of supersaturation which causes stones to form in the bladder. These stones often tend to recur in cats if their diet is not changed often.

To prevent these stones, we try to reduce the amount of phosphorus, magnesium and protein, using high quality protein so as to minimize the concentration of urea in the urine. To dissolve these stones, we add urine acidifying substances such as DL-methionine or calcium sulfate for example.

Finally, to prevent recurrence of lithiasis, calcium intake is often reduced to secondarily prevent the formation of calcium oxalate stones. Antibiotic treatment can also be used in dogs to eliminate the transformation of urea into ammonia.

Other types of calculations

Urate stones :

These stones represent about 10% of cases of urolithiasis in dogs. However, they are very rare in cats. Their formation is caused by the buildup of uric acid in the urine. Two different causes are at the origin of this accumulation: the first is linked to a defect in the metabolism of uric acid observed during a hepatic shunt.

This is because the transformation of purine takes place in the liver and leads to the formation of allantoin, which is eliminated with the urine. The second cause is observed in certain breeds such as the Dalmatian, or in the Yorkshire: normally the purine is degraded into hypoxanthine then into xanthine, then into uric acid, this last reaction occurs thanks to a uricase which is often absent in the Dalmatian . This results in an accumulation of uric acid in the urine of dogs of this breed.

Oxalate stones :

The dog breeds most often predisposed to this condition are the Miniature Schnauzer, Yorkshire, Lhasa Apso, Shih-Tzu and in cats, Burmese, Himalayan and Persian. These stones are quite common in middle-aged to old animals and affect males much more often than females. Their formation results from an excessive saturation of the urine with oxalic acid and calcium. Urinary oxalic acid arises from the metabolism of ascorbic acid, glycine and tryptophan, but urinary oxalate concentration increases primarily with dietary oxalate intake.

Calcium absorption varies depending on the parathyroid hormone. This association also varies the tubular reabsorption and the mobilization of bone calcium. Phosphorus and sodium also play a role in the absorption of calcium. Finally, the addition of citric acid in the ration, metabolizing into bicarbonate, induces a slight metabolic alkalosis, increasing the tubular reabsorption of calcium, and decreasing its content in the urinary tract.

In addition, the formation of these stones is favored by the acidity of the urine: the treatment of the dissolution of struvite stones often promotes the formation of oxalates via the urinary acidification generated. The theory is to promote alkalinization of urine to prevent oxalate formation, but unlike struvite stones, oxalate stones cannot be dissolved through food.

Cystine stones :

Cystine stones are rare stones in dogs and cats, and almost only affect males. Dachshunds and Artesian Bassets are particularly predisposed to it. This is a metabolic error that leads to bind a cysteine ​​molecule (cysteine ​​is a semi-essential sulfur amino acid, derived from food or formed from methionine in the body) to other amino acids to form a cystine molecule.

The cystine formed in this way does not reabsorb into the renal tubules, which would lead to the accumulation of cystine in the bladder. To this are added predisposing factors, the more concentrated or acidic the urine, the more the formation of these stones is favored.

Sources :

  • Affinity-Advance veterinary. Product guide 2003
  • Baker DH, Czarnecki-Maulden GL, Comparative nutrition of dogs and cats. Annual Review of Nutrition 1991
  • Finco DR, Brown SA, Cowell SA et al. Effects of dietary phosphorus and protein in dogs with chronic renal failure. American Journal of Veterinary Research 1992
  • Klahr S, Levey AS, Beck GJ, et al. The effect of dietary protein restriction and blood pressure control on the progression of chronic renal disease
  • Laboratoire Léo Santé Animale. Guide de nutrition 2001
  • Levey AS, Adler S, Caggiula AW, et al. Effects of dietary protein restriction on the progression of moderate renal disease. In the modulation of diet in renal disease study. Journal of the American Society of Nephrology 1996


Clémentine. M.

Naturopath – Aromatherapist / Herbalist – Phytotherapist
Consultant in clinical phyto-aromatherapy and ethnomedicine

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