How common are urate uroliths in female Dalmatians?

Recently, I received a letter from an inquisitive Dalmatian owner whichstated in part:

"I have a 9-year-old female Dalmatian that has been diagnosed witha urinary tract infection because of red blood cells found in urine aspiratedfrom her urinary bladder during an annual physical exam. She does not havea problem urinating and her urine appears very clear; it is not bloody.My vet has tried two types of antibiotics (cephalexin first and trimethoprim-sulfathree weeks later). Even though her urine is not bloody, red blood cellsare still present in the urinalysis. My vet also prescribed a special dietto prevent urate stones from forming even though no crystals were foundin her urine. Is there a probability of urinary stones even though thereare no crystals in her urine? Is the urinary tract infection persistingbecause of stones?"

How would you respond to these questions? Is detection of red cells byurinalysis a reliable index of bacterial urinary tract infection? Does thepersistent microscopic hematuria indicate the probability of uroliths? Areurate uroliths common in female Dalmatian dogs? Is there evidence to supporta feeding protocol designed to prevent urate uroliths in this dog?

Hematuria significance

What is the significance of the hematuria?

If RBCs identified in urine of this Dalmatian were associated with bacterialinfection, one would expect to also find concomitant evidence of inflammation(i.e. pyuria associated with varying degrees of proteinuria). Furthermore,detection of bacteria in association with pyuria, hematuria and proteinuriawould indicate that the inflammatory lesion is active and caused or complicatedby infection. If the information provided by the owner about urinalysisis correct, was prolonged treatment of this dog with antimicrobics warranted?

If RBCs were detected in urine sediment of this dog in absence of whitecells, noninfectious causes of hematuria should be considered before prescribingantimicrobics. Since the dog was asymptomatic, microscopic hematuria associatedwith collection of urine by cystocentesis should be investigated (See Diagnotein DVM Newsmagazine, July 1997, page 11S). This mechanism of hematuria couldbe easily evaluated by performing a urinalysis on a voided urine sample.Collection and analysis of the voided sample should be scheduled a few daysafter cystocentesis to allow any hemorrhage associated with needle-inducedtrauma to the bladder time to heal.

Predisposition

Are urate uroliths common in female Dalmatian dogs?

It is common knowledge that Dalmatians are predisposed to urate urolithiasis.But, does this generality apply to both males and females? To answer thisquestion, consider the following epidemiologic data generated by the MinnesotaUrolith Center.

From 1981 to 2000, we analyzed 7,560 uroliths retrieved from 7,068 maleand 282 female Dalmatians (the gender of 240 Dalmatians was not identified).Of these 7,560 uroliths, 95 percent were composed of urate (especially ammoniumurate). However, female Dalmatians comprised only 3 percent of all Dalmatianswith urate uroliths; 97 percent occurred in males. The explanation of thismarked disparity between the frequency of detection of urate uroliths inmale and female Dalmatians requires additional study.

Returning to the question posed at the beginning of this discussion,is there evidence to warrant feeding a diet to prevent urate uroliths inthis female Dalmatian? In light of our observations that diagnosis of urateuroliths in female Dalmatians is approximately 30 times less likely comparedto male Dalmatians, and in absence of clinical data indicating that thisfemale Dalmatian has urolithiasis, what is your conclusion? Isn't it apparentthat the benefit of management protocols designed to minimize urate urolithsin female Dalmatians should be determined after proper evaluation of eachindividual patient?

Other types

Have other types of uroliths been observed in Dalmatians?

The answer is...yes! Not all uroliths formed by Dalmatians are composedof urates. Of the 282 uroliths formed by female Dalmatians and submittedto our Center for analysis, 194 (69 percent) were urate, 6 (2 percent) werestruvite, 2 (<1 percent) were xanthine, 32 (11 percent) were compound,and 50 (18 percent) were of mixed composition. Of the 7,068 uroliths formedby male Dalmatians, 6,828 (97 percent) were urate, 30 (0.4 percent) werestruvite, 50 (0.7 percent) were xanthine, 19 (0.3 percent) were calciumoxalate, 78 (1.1 percent) were compound, and 96 (1.4 percent) were of mixedcomposition.

This data underscores the importance of quantitative analysis of urolithsretrieved from all Dalmatians. To emphasize the importance of this recommendation,consider it in the following perspective. If a Dalmatian forms a struviteurolith, the rate of occurrence of struvite is 100 percent for this Dalmatian.This patient is unlikely to benefit from medical protocols designed specificallyfor management of urate uroliths.

The mission of the Minnesota Urolith Center is to assist in sustaininghigh-quality veterinary medical care by providing quantitative analysisof uroliths.

This diagnostic service is available without charge, provided urolithsare submitted with relevant data about the patient. To obtain a proper urolithanalysis submission from, FAX a request to (612) 624-0751.