Urinary acidification in the prevention and treatment of feline struvite urolithiasis

Two groups of 12 cats were fed ad libitum an experimental dry expanded ration high in magnesium (0.37%, dry matter basis) and similar to most commercial dry cat foods in all other nutrients. The diet of one of the groups contained 1.5% ammonium chloride, which was added to the diet before processing. Urethral obstruction developed twice in 7 of the 12 cats fed the ration without ammonium chloride. Of the 5 remaining cats in that group, 2 had calculi in the urinary bladder and urethra at necropsy. In contrast, only 2 of the 12 cats fed the ration containing ammonium chloride had urethral blockage once; neither cat had another blockage. Both cats had been catheterized twice as paired controls before urethral obstruction. One of these 2 cats died from a urinary tract infection apparently introduced through the indwelling catheter, and at necropsy there were 2 small calculi in the urethra. At the end of the study, only 1 other cat fed the ammonium chloride diet had a calculus in the urinary bladder at necropsy; this cat had not had a urethral obstruction throughout the study. After each cat had 2 urethral blockages, its diet was changed. Four cats were fed the ration containing ammonium chloride and 3, a dry, commercial ration. Of the 4 cats fed the diet containing ammonium chloride, none developed another urethral obstruction within 6 months, and at necropsy, no calculi were in the urinary bladder or urethra. Two of the 3 cats fed the commercial ration experienced urethral blockage within 3 months. These 2 cats were then fed the diet containing ammonium chloride.(ABSTRACT TRUNCATED AT 250 WORDS)