Veterinary Medicine - October 2008 - (Page 550)

Urolithiasis PEER-REVIEWED initiated before urolith recovery may infrequently cause the shell surface and the patient’s urine to be sterile; however, viable bacteria may still be present in the urolith’s center.10 Although bacteria do not always play a primary role in urolith formation, bacterial infection often accompanies uroliths and represents a complicating factor in treatment. Often a urolith is not readily available for direct analysis. In those cases, using the patient’s signalment to establish any potential breed, age, or sex predisposition together with radiographic examination ndings, bacterial culture, and urinalysis results from a fresh, nonrefrigerated sample can provide valuable information regarding potential urolith composition. For example, isolating urease-producing bacteria from the urine is a strong indication of struvite composition, particularly in dogs. Although identifying speci c urine crystals may help determine the urolith composition, several factors must be kept in mind when evaluating the importance of crystals. Many of the commonly recognized crystals can be considered normal ndings in urine samples. Their presence does not necessarily indicate that urolith formation will follow or that the composition of any given urolith will match the crystal type identi ed. In addition, uroliths can be found in some patients that have no identi able urine crystals. Treatment and prevention plans should always be in response to actual urolith or plug formation and not in response to the presence of crystals alone. Voiding urohydropropulsion in dogs and cats* Abdominal radiography and ultrasonography can help determine the number of urocystoliths and if they are suitable in size and contour for passage through the patient’s distended urethra. Small (about 1 to 5 mm) uroliths with a smooth contour are best-suited for voiding urohydropropulsion. The urethra size will vary according to the patient’s species and sex, so these factors are important determinants of success with this technique. After determining that the urocystoliths are suitable for urohydropropulsion, anesthetize or heavily sedate the patient. Distend the bladder with saline solution through a urethral catheter. After removing the urethral catheter, position the anesthetized or sedated patient in an upright position with the spine perpendicular to the surface below. Apply steady pressure with manual compression to the bladder. Maintain a voiding stream of urine through the urethral lumen, propelling uroliths out with the voided urine. Collect the voided urine in a container so that uroliths can be recovered for quantitative analysis and culture. Repeat the procedure as needed to remove all the uroliths, performing imaging techniques as needed to ensure complete elimination of uroliths.1,2 *An assistant is needed to hold the patient in the upright position. REFERENCES 1. Lulich JP, Osborne, CA, Sanderson SL, et al. Voiding urohydropropulsion. Lessons from 5 years of experience. Vet Clin North Am Small Anim Pract 1999;29(1):283-291. 2. Lulich JP, Osborne CA, Carlson M, et al. Nonsurgical removal of urocystoliths in dogs and cats by voiding urohydropropulsion. J Am Vet Med Assoc 1993;203:660-663. compositions. Few studies are published in peer-reviewed journals that evaluate the ef cacy of speci c diet formulations in dogs or cats with naturally occurring uroliths.19,20 Table 2 is a quick reference for urolith diagnosis, treatment, and prevention recommendations. Struvite Struvite (magnesium ammonium phosphate hexahydrate) uroliths are one of the most common uroliths in dogs and cats. Although struvite was the most prevalent urolith composition overall in dogs from 1981 to 2005 (43.5%) according to one study,21 the occurrence of struvite uroliths in dogs steadily declined during that same period and struvite became the second most prevalent urolith composition in dogs beginning in 2004 (39%).21 A study at the Minnesota Urolith Center analyzing uroliths in cats from 1981 to 2002 also revealed a change in struvite urolith prevalence.22 In 1981, struvite uroliths represented most uroliths in cats (78%), SPECIFIC UROLITH CHARACTERISTICS, TREATMENTS, AND PREVENTION The following discussion focuses on the characteristics of speci c therapeutic and prevention options. Table 1 lists many of the diet options for the dissolution and prevention of canine and feline uroliths. The entries are based primarily on the manufacturer’s diet formulation descriptions for nutritionally managing animals with particular crystal and urolith but a steady decline was seen over several years, with struvite decreasing to an overall prevalence of about 33% from 1994 to 2002. Beginning in 2003, the frequency of struvite uroliths in cats began to notably increase, reaching 48.1% in 2005 and again establishing struvite as the most prevalent urolith composition identi ed in cats at the Minnesota Urolith Center.22 A separate California study analyzing a large number of uroliths in cats over a similar period supports the trend in recent increases in struvite uroliths.23 The shifts in urolith frequency in both dogs and cats have been theorized to be the result of commercial maintenance diet reformulation and the increased use of therapeutic diets designed to dissolve or prevent uroliths.22,23 However, this theory does not seem to explain the fact that during the same 25-year period, the mineral composition of urethral plugs in cats has remained consistently and primarily struvite (87% in 2005).22 550 October 2008 VETERINARY MEDICINE

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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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