Stalking stones: An overview of canine and feline urolithiasis - Veterinary Medicine
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Stalking stones: An overview of canine and feline urolithiasis
Did you know that a new type of urolith has been found in cats? Should you institute preventive therapy if you identify only crystalluria? Is antibiotic therapy automatically warranted in animals with indwelling urinary catheters? This internist revamps your knowledge on diagnosing, treating, and preventing urolithiasis.



Compound uroliths are found in cats (< 5% prevalence)22 and dogs (8.5% prevalence).21

Characteristics. Compound uroliths are uroliths in which the center is at least 70% one mineral type and the outer layer is at least 70% of another mineral type.21

Treatment and prevention. Since the two primary mineral types may have conflicting treatment protocols, quantitative analysis to determine composition is especially important.48 In general, treat and prevent these uroliths by using the appropriate protocol for each primary mineral type as identified above. Compound uroliths containing calcium oxalate have become more prevalent during the last several years,14 limiting medical dissolution opportunities. When a compound urolith has calcium oxalate as one of the primary mineral types and the second mineral type is one that is amenable to medical dissolution, it is advisable to direct prevention efforts toward the calcium oxalate component. When struvite is combined with calcium oxalate in a compound urolith, eradicate any urinary tract infection as well.48

Dried solidified blood

The dried solidified blood urolith is a composition recently recognized in cats.49

Characteristics. These uroliths are found in both the upper and lower urinary tract and differ from other uroliths in that they usually contain no crystalline material. Dried solidified blood uroliths appear to be formed from organic material, are generally radiolucent, and are not identifiable by ultrasonography.49 Contrast radiography may suggest urinary tract obstruction but not reveal a discrete urolith. No known sex predisposition exists. Domestic shorthaired and longhaired cats are most commonly affected. The mean age of cats with dried solidified blood uroliths in a report of 49 affected cats was 9 years.49

Treatment and prevention. No medical dissolution or prevention protocols are available. Because of the difficulty in identifying the urolith by imaging, surgical removal has been the primary treatment method. Because hematuria was identified in all cats for which urinalysis results were available, searching for inflammatory or ischemic causes of hematuria is recommended. In addition, increasing fluid intake (e.g. feeding canned food) is encouraged.

Nephroliths and ureteroliths

Although most uroliths in dogs and cats are found in the bladder or urethra, uroliths are also occasionally located in the renal pelves or ureters.

Characteristics. Upper urinary tract uroliths are most commonly composed of struvite or calcium oxalate, with calcium oxalate being the more prevalent.50

Treatment. In cases in which nephroliths or ureteroliths are suspected to be primarily struvite, medical dissolution can be attempted, provided that an emergency circumstance does not preclude that option. Medical dissolution of a suspected struvite ureterolith is unlikely since the urolith's location does not allow consistent contact with urine that is acidic and undersaturated with struvite-forming minerals as a result of dietary therapy.10 Surgical intervention or lithotripsy is the primary option when an upper urinary tract urolith is suspected to be composed of calcium oxalate and warrants removal.


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