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.


VETERINARY MEDICINE


Nonobstructed patients


Voiding urohydropropulsion in dogs and cats
Uroliths can be eliminated in patients without a urethral obstruction by voiding urohydropropulsion (see the boxed text titled "Voiding urohydropropulsion in dogs and cats") surgical removal, lithotripsy, medical dissolution, or new minimally invasive interventional radiographic and endoscopic techniques.

Voiding urohydropropulsion. Urethral size is a limiting factor for voiding urohydropropulsion; a male cat with urocystoliths > 1 mm in diameter is not a candidate for this procedure unless the cat has undergone perineal urethrostomy.4,5 Voiding urohydropropulsion is also a poor choice for patients with a urethral obstruction, a history of recent urinary bladder surgery, or an unresolved urinary tract infection.6

Surgery. Depending on the location of the uroliths, surgical intervention, such as removing uroliths through an incision into the kidney, ureter, bladder, or urethra or, occasionally, removing a severely affected kidney or ureter, may be indicated. Radiographic or ultrasonographic imaging is always recommended after surgically removing uroliths to make sure no uroliths remain.7

Lithotripsy. Lithotripsy can be accomplished by intracorporeal electrohydraulic, laser, or ultrasonic techniques or by an extracorporeal shock wave method. Intracorporeal electrohydraulic lithotripsy breaks up uroliths by using repetitive shock waves conducted through a flexible probe placed endoscopically next to the targeted urolith. Laser lithotripsy uses light-amplified thermal energy to fragment uroliths through fibers endoscopically positioned adjacent to the selected urolith.8 Ultrasonic lithotripsy uses high-frequency sound waves delivered to the urolith through an endoscopically placed electronic probe. Extracorporeal shock wave lithotripsy breaks up uroliths through focused shock waves generated from equipment positioned outside the patient's body.

The urolith fragments produced through lithotripsy must be small enough for the patient to eliminate them through voided urine, or they must be extracted by using suction devices or grasping instruments. The use of lithotripsy is limited by a patient's size and sex, the availability of the specialized equipment, and the size, number, and composition of uroliths involved.

Traditionally, intracorporeal electrohydraulic lithotripsy techniques involve transurethral passage of equipment, making these methods best-suited for fragmenting cystoliths and urethroliths in female dogs and cats, male dogs weighing > 11 lb (5 kg),9 and male cats that have had a perineal urethrostomy performed. Extracorporeal shock wave lithotripsy has been used primarily for fragmenting nephroliths and ureteroliths in dogs only. Although laser lithotripsy use is becoming more widespread, most of these techniques are limited to a small number of institutions and large, private referral practices.

Medical dissolution. Medical dissolution through a special diet can be used as a primary means of urolith elimination or as a secondary procedure after urolith removal by other methods to ensure that all uroliths or fragments have been eradicated. When used as a primary method of urolith elimination, medical dissolution techniques generally require feeding only the prescribed diet for one month beyond radiographic or ultrasonographic evidence of urolith dissolution. Complications from obstruction and the lack of consistent exposure to urine altered by diet and medication make dissolution protocols unlikely to be effective for treating uroliths located in the ureter or urethra.10 Medical dissolution protocols are discussed in "Specific urolith characteristics, treatments, and prevention."


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Source: VETERINARY MEDICINE,
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