Veterinary Medicine - October 2008 - (Page 560)

Urolithiasis PEER-REVIEWED predisposing defect make prevention important in dogs that have experienced an episode of cystine urolith formation. A prevention protocol consists of administering tiopronin (15 mg/kg orally twice a day), adding water to the patient’s food, and alkalinizing the urine with potassium citrate (100 to 150 mg/kg once a day or in two divided doses/day).14 The goal of alkalinization should be to achieve a urine pH of 7 to 7.5.24 An alternative prevention protocol calls for feeding Prescription Diet u/d plus administering either tiopronin or d-penicillamine at 10 to 15 mg/kg orally every 12 hours.46 Although Prescription Diet u/d is considered a maintenance diet, it has a low protein content, so monitor dogs fed this diet long-term for protein depletion by performing a serum chemistry pro le at least every six months. Although the incidence of feline cystine uroliths is low, the frequency of recurrence in affected cats appears high.44 For cats, a diet for managing kidney disease, such as canned or moistened dry Prescription Diet k/d or similar alkalinizing renal failure diets from other manufacturers, is recommended. Treatment and prevention. No method of medical dissolution is available, and surgical removal is often necessary, although voiding urohydropropulsion can be attempted if the uroliths are small enough. Lithotripsy is another treatment option. Recurrence is possible but uncommon. The only recommendations for prevention are to increase water consumption and avoid diets high in plant proteins. Prescription Diet d/d (Hill’s Pet Nutrition) may be appropriate for prevention because of its low plant protein content. nary tract and differ from other uroliths in that they usually contain no crystalline material. Dried solidi ed blood uroliths appear to be formed from organic material, are generally radiolucent, and are not identi able 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 solidi ed 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 dif culty in identifying the urolith by imaging, surgical removal has been the primary treatment method. Because hematuria was identi ed in all cats for which urinalysis results were available, searching for in ammatory or ischemic causes of hematuria is recommended. In addition, increasing uid intake (e.g. feeding canned food) is encouraged. Compound 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 Silicate Silicate uroliths are uncommon in dogs, accounting for < 1% of all urolith types analyzed with the Minnesota Urolith Center from 1981 to 2006.21 Silicate uroliths are rarely reported in cats.5,40 Characteristics. These uroliths are grayish-white to brown and frequently look like jackstones.47 They are radiopaque and found most frequently in the bladder and urethra. Silicate uroliths are composed primarily of amorphous silica crystals. A predisposition exists for German shepherds and Old English sheepdogs.24 The cause of silicate uroliths is unknown but may be diet-related. Diets high in corn gluten or rice and soybean hulls are suspected to increase the incidence of silicate urolith formation.24 No relationship has been established between urine pH and silicate urolith formation. Treatment and prevention. Since the two primary mineral types may have con icting 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 identi ed 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 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 Dried solidiﬁed blood The dried solidi ed blood urolith is a composition recently recognized in cats.49 Characteristics. These uroliths are found in both the upper and lower uri- 560 October 2008 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - October 2008

Veterinary Medicine - October 2008 Contents Leading Off Clinical Exposures Idea Exchange Stalking Stones Vaginitis in Dogs CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - October 2008

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