Urolithiasis is a common diagnosis in general small-animal practice. Previous studies estimated that calcium oxalate uroliths
occur most frequently in cats (46% of cases), followed by magnesium ammonium phosphate (43%) and ammonium urate (5%) uroliths;
however, the relative frequency of these mineral types has changed over the previous decades and may change again in the future
as new diets are introduced.1 Unfortunately, urolith recurrence is a common event, and pet owners should be prepared for this eventuality.
This study suggests that cats have less frequent urolith recurrence than do dogs, particularly of calcium oxalate uroliths,1 and that no specific cat breed is at increased risk for recurrence. However, true recurrence must be distinguished from
urolith persistence (incomplete removal of all uroliths). Abdominal radiography or ultrasonography immediately after urolith
removal is recommended to confirm removal success and to help you determine what short- and long-term management may be needed.
Because these imaging tests are not systematically performed by all clinicians, results in this study may have been skewed
by persistent calculi being incorrectly counted as recurrent. In addition, the true recurrence rate may have been underestimated
in this study because subsequently removed stones may not have been sent in for analysis under the assumption that the urolith
mineral type was likely the same as the first occurrence. This hypothesis was tested by sending questionnaires to veterinarians
who had diagnosed ammonium urate uroliths in cats in 1998. The results showed that in five of 29 cases, recurrent uroliths
were not submitted for mineral analysis, thus increasing the rate of first recurrence from 10.9% to 13.1%. To what extent
this study bias may have affected the calculated recurrence rate for all three mineral types of the entire six-year period
At this time, the optimal way to decrease the likelihood of urolith recurrence is to prescribe an appropriate diet, manipulate
urine pH, and appropriately treat or prevent urinary tract infections, depending on urolith type. Canned food is generally
recommended over dry food in order to dilute urine and, thus, decrease the likelihood that urine will be supersaturated by
the implicated mineral type. Other dietary management strategies may include increasing the frequency of feedings throughout
the day to increase water consumption and providing a highly digestible diet that reduces fecal water loss and promotes diuresis
through increased solute load excretion. Some feline therapeutic diets are formulated to maintain a neutral urine pH and may
contain urolith formation inhibitors.
Albasan H, Osborne CA, Lulich JP, 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.
The information in "Research Updates" was provided by Erika Meler, DVM, MS, and Barrak Pressler, DVM, PhD, DACVIM, Department
of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.
1. Osborne CA, Lulich JP, Kruger JM, et al. Analysis of 451,891 canine uroliths, feline uroliths, and feline urethral plugs
from 1981 to 2007: perspectives from the Minnesota Urolith Center. Vet Clin North Am Small Anim Pract 2009;39(1):183-197.