Albasan H, Osborne C, Lulich J, et al. Rate and frequency of recurrence of uroliths after an initial ammonium urate, calcium oxalate, or struvite urolith in cats. J Am Vet Med Assoc. 2009;235(12):1450-1455.
This case-controlled study was performed through the Minnesota Urolith Center. The objective was to determine the frequency of and interval until recurrence after initial ammonium urate, calcium oxalate and struvite uroliths in cats and whether breed, age, or gender was associated with increased risk for recurrence. In 1998, 4,435 cats were evaluated for an initial urolith episode and between 1998 and 2003 for recurrence episodes. Ammonium urate uroliths were found in 221 cats and 13.1% had an initial recurrence with a mean interval to recurrence of 22 months. Calcium oxalate uroliths were found in 2,393 cats and 7.1% had an initial recurrence with a mean interval of 25 months. Of 1,821 cats with struvite uroliths, 2.7% had a recurrence with a mean interval of 29 months. In all three types of uroliths, the largest percentage was located in the lower urinary tract. The study noted a low frequency of recurrence after struvite uroliths. The authors also noted it is likely that calcium oxalate and purine uroliths require at least 6 months to recur. Infection-induced struvite uroliths constitute an estimated 1 to 2% of uroliths retrieved from cats. An association was found in this study between recurrent episodes after initial calcium oxalate and struvite uroliths and older cats. The study also indicated a possible association between Persians and ammonium urate uroliths. Norwegian Forest Cats and Manx cats are at an increase risk for development of calcium oxalate uroliths, yet the number of these cats was small in this study. The majority of the uroliths (94%) found in the first recurrent episodes were identical to that of the initial urolith. Therefore, the composition of an initial urolith may be used as an estimate of the composition of subsequent uroliths. [VT]
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