Back

NUTRITIONAL FACTORS INVOLVED IN STRUVITE-RELATED LOWER URINARY TRACT DISEASE

First broadcast on www.provet.co.uk  as part of it's Focus On Nutrition Week 

 


This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Cats can develop a serious disease of the lower urinary tract (called FUS or FLUTD) which can be due to the formation of crystals of "struvite" in the urine. Some of the factors involved in the formation of struvite crystals, and also the plugs or stones which can block the urinary tract, can be controlled by diet. 

"Struvite" is the common name for a chemical called magnesium ammonium phosphate hexahydrate. In the urine struvite  crystals aggregate together and can either form small mineralised stones (called uroliths) or become incorporated with protein into a softer plug of material. Stones can cause inflammation of the urinary tract (eg cystitis, or urethritis) or they, and the plugs, can cause an obstruction - usually in the urethra, the tube which carries the urine away from the bladder. This problem is more common in male cats than females. If they block the urinary tract the cat cannot pass urine which builds up inside the bladder, and can be life-threatening if it is not treated.

The chemical components needed to be present in the urine to form struvite are :

  • Magnesium
  • Phosphorus
  • Ammonium (derived from metabolism of the amino acids in protein)
  • Water 

The objective of dietary management is to prevent the formation of the struvite crystals by reducing the concentrations of it's chemical components in the urine, and to modify the acidity of the urine to discourage their precipitation out of solution.

Cats have a nutritional requirement for magnesium, phosphorus, and particularly for protein (which forms ammonium) and so it is not possible to compile a diet which does not contain them. However, the concentration of these components can be minimised and excess quantities reduced.  

Rations aimed at reducing the risk of struvite crystal formation therefore contain less than 20mg/100 kcal of food, and just over the minimal requirement for phosphorus and protein (the precursor for the ammonium ion in the urine).

Because the struvite crystals form best in alkaline conditions a diet that produces an acidic urine is fed. Usually these diets are formulated to maintain the urine at a pH of 6.4 or less.

Many thousands of cats worldwide now get less recurrence of this potentially fatal disease thanks to the development of these diets. What is even more remarkable, is that applying the same basic clinical nutrition principles has allowed the development of diets which can actually dissolve stones that are already formed in the urinary bladder of cats and dogs. This must be one of the most important clinical nutrition developments for the benefit of pets in the past Century.

 

Updated October 2013