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


Ureteroliths will sometimes pass into the bladder or move retrograde into the kidney pelvis.50 In some cases, ureterolith passage into the bladder can be facilitated by administering smooth muscle relaxants such as prazosin (Minipress—Pfizer; 0.25 to 0.5 mg/cat orally twice a day; 1 mg/15 kg orally once or twice a day in dogs), fluid therapy, and diuretics. Amitriptyline can also be used in dogs for ureteral smooth muscle relaxation (1 to 2 mg/kg orally once a day). If the ureterolith has not passed from the ureter in three to five days with medical management, surgical intervention or lithotripsy may need to be considered.

Consider removing an affected kidney and ureter if their function is severely impaired because of a nephrolith and the other kidney is functioning adequately as demonstrated by the results of laboratory tests and an excretory urogram or nuclear scintigraphy. Removing a urolith by surgically incising the renal pelvis or ureter is also an option but may cause permanent damage to these organs. The introduction of a percutaneous approach to surgical incision of the kidney for the purpose of urolith extraction, lithotripsy, or ureteral stent placement holds promise for decreasing associated damage to the affected area.16,17

In general, nephrotomy and ureterotomy should only be undertaken if the urolith is severely compromising renal function; is associated with severe pain, hematuria, or infection; or is steadily enlarging and causing obvious damage to kidney tissue. Otherwise, the best option is often monitoring the patient's status by periodically evaluating the results of serum chemistry profiles, urinalyses, and abdominal imaging; observing for progressive clinical signs; providing pain management as needed; and implementing a preventive plan appropriate for the suspected urolith type. The evaluation interval will vary with the patient's condition. Relatively asymptomatic patients may only require evaluation every two to three months, while patients exhibiting more clinical signs may warrant daily to weekly evaluation.

Mary Bowles, DVM, DACVIM
Department of Veterinary Clinical Sciences
Center for Veterinary Health Sciences
Oklahoma State University
Stillwater, OK 74078

REFERENCES

1. Osborne CA, Lulich JP, Ulrich LK, et al. Feline crystalluria. Detection and interpretation. Vet Clin North Am Small Anim Pract 1996;26(2):369-391.

2. Feeney DA, Weichselbaum RC, Jessen CR, et al. Imaging canine urocystoliths. Detection and prediction of mineral content. Vet Clin North Am Small Anim Pract 1999;29(1):59-72.

3. Weichselbaum RC, Feeney DA, Jessen CR, et al. Urocystolith detection: comparison of survey, contrast radiographic and ultrasonographic techniques in an in vitro bladder phantom. Vet Radiol Ultrasound 1999;40(4):386-400.

4. 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.

5. 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(5):660-663.

6. Lulich J, Osborne CA. Beyond the stone age: minimally invasive techniques, in Proceedings. 25th Am Coll Vet Intern Med Forum, 2007.

7. Lulich JP, Osborne CA, Polzin DJ, et al. Incomplete removal of canine and feline urocystoliths by cystotomy (abstr). J Vet Intern Med 1993;7:124A.

8. Grant DC, Werre SR, Gevedon ML. Holmium: YAG laser lithotripsy for urolithiasis in dogs. J Vet Intern Med 2008;22(3):534-539.

9. Adams LG, Berent AC, Moore GE, et al. Use of laser lithotripsy for fragmentation of uroliths in dogs: 73 cases (2005-2006). J Am Vet Med Assoc 2008;232(11):1680-1687.

10. Osborne CA, Lulich JP, Polzin DJ, et al. Medical dissolution and prevention of canine struvite urolithiasis. Twenty years of experience. Vet Clin North Am Small Anim Pract 1999;29(1):73-111.


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