Veterinary Medicine - October 2008 - (Page 558)

Urolithiasis PEER-REVIEWED uroliths; treat these with appropriate antibiotics. Catheter-assisted urolith retrieval Prevention. Preventing urate uroliths in dogs can often be accomplished by feeding Prescription Diet Canine u/d with or without allopurinol (5 to 10 mg/kg orally once or twice a day). Preventing urate uroliths in cats is generally successful by feeding them a kidney disease management diet such as Prescription Diet Feline k/d, which is alkalinizing and proteinrestricted.34 Patients with urate uroliths associated with portovascular shunts should undergo surgical correction for the anomaly, if possible, to prevent further urolith formation. For this procedure, the patient may require anesthesia or sedation. Surgically scrub the penis and prepuce or vulva, and wear sterile gloves for this procedure. Depending on the patient’s size, insert the tip of a red rubber, latex, silicone, or polypropylene, 3.5- to 8-F, open- or close-ended urinary catheter transurethrally to the neck of the bladder. Larger-diameter catheters may facilitate urolith retrieval. If a close-ended urinary catheter is used, make certain the eyelets at the distal end of the catheter are positioned in the bladder neck or beyond. Distend the patient’s bladder with saline solution, if it is not already distended with urine. Agitate the distended bladder through the abdominal wall while vigorously aspirating urine and small uroliths into the catheter with a 10-ml or larger syringe. Filtering the aspirated urine through gauze or other netting material facilitates recovery of all uroliths present.1 REFERENCE 1. Adams LG, Syme HM. Canine lower urinary tract diseases. In: Ettinger SJ, Feldman EC, eds. Textbook of veterinary internal medicine. 6th ed. St. Louis, Mo: Elsevier Saunders, 2005;1850-1874. Xanthine (purine) Xanthine is a purine urolith recognized more recently in cats but also reported in Cavalier King Charles spaniels and dachshunds. These two dog breeds are thought to have an inborn error of purine metabolism, which leads to xanthine formation.24,40 In cats, a familial or congenital defect in the activity of xanthine oxidase is suspected to be the primary cause of xanthine urolith formation.41 Characteristics. Xanthine crystals resemble uric acid crystals or are amorphous. Xanthine uroliths are usually a few millimeters in diameter, have a smooth surface, and are yellow, tan, or light-brown. The uroliths are radiolucent and often must be detected through positive double-contrast cystography or urethrography or high-frequency ultrasonography. Xanthine uroliths have been found primarily in the lower urinary tract, although they occasionally occur in the upper urinary tract. Affected cats’ urine may be a mustard-yellow color. Male cats appear to be predisposed to xanthine formation, and the average age of affected cats at the time of diagnosis is 2.8 years.34 An incidence of 0.1% in cats was reported by the Minnesota Urolith Center in 2006.22 Although allopurinol administration predisposes both cats and dogs to xanthine formation, most affected cats have not received this drug.34 Treatment and prevention. No medical dissolution protocol exists for this urolith type. Treatment consists of removal or lithotripsy. The recommended prevention protocol for dogs and cats consists of feeding them a protein-restricted, alkalinizing diet such as Prescription Diet k/d.41 Because allopurinol administration without purine restriction can cause xanthine urolith formation, always feed a purine-restricted diet to patients receiving allopurinol for any reason.23,39,42 are detected. Affected dog breeds include English bulldogs, Newfoundlands, dachshunds, Irish terriers, basset hounds, and bullmastiffs.14 Male dogs are more commonly affected than female dogs except in Newfoundlands, in which both sexes seem equally affected. Male and female cats appear to be equally affected, and cystine urolithiasis is diagnosed at a mean age of 4.1 years. Domestic shorthaired and Siamese cats are the most commonly affected.25,44 Treatment. An alkalinizing, low-protein diet, such as Prescription Diet u/d, is recommended for treating cystine uroliths in dogs . Thiol disul de exchange drugs, d-penicillamine and MPG, or tiopronin (Thiola—Mission Pharmacal), are used to dissolve these uroliths in dogs. These drugs combine with the precursors of cystine to produce a more soluble product. In dogs, combining a thiol exchange drug with Prescription Diet u/d appears to enhance cystine urolith dissolution.45 D-penicillamine is administered at a dosage of 15 mg/kg orally twice a day, and tiopronin is administered at a dosage of 20 mg/kg orally twice a day.24 The thiol disul de exchange drugs are most effective at a neutral to alkaline urine pH. D-penicillamine’s main side effect is vomiting, which can usually be avoided by giving the drug with food, adminis- Cystine Cystine uroliths are uncommon in dogs (1% prevalence)21 and even less common in cats (< 1% prevalence).34 Characteristics. Cystine crystals are large, at, and hexagonal, and their presence in urine should always be considered abnormal. Cystine crystals precipitate in acid urine to form uroliths that are small, spherical, and light-yellow, light-brown, or light-green. These uroliths are relatively radiolucent and commonly require contrast cystography or urethrography or ultrasonography for detection. In dogs and cats, cystine urolith formation is associated with an inherited disorder that causes insuf cient renal tubular reabsorption of cystine and other amino acids.43 Affected dogs are commonly 4 to 6 years old at the time that cystine uroliths 558 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

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.