Today's Veterinary Practice

SEP-OCT 2015

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Today's VeTerinary PracTice | september/october 2015 | tvpjournal.com Feline sTruViTe & calcium oxalaTe uroliThiasis Peer reviewed 18 recommended. In both cases, the complication rate associated with surgery (eg, compromised renal function and ureteral stricture) is high. Cats with obstructive ureterolithiasis are best managed with ureteral stents or subcutaneous ureteral bypass (SUB). Intracorporeal laser lithotripsy via cystoscopy may be used to treat cystoliths in female cats. Emergent Therapy Hyperkalemia is a potentially life-threatening electrolyte disturbance that may occur in cats with postrenal azotemia caused by urethral obstruction or rupture of the urinary bladder or urethra. In cats suspected of having urethral obstruction, fndings that suggest hyperkalemia include: • Elevated serum potassium, blood urea nitrogen, and creatinine concentrations • Bradycardia and electrocardiographic findings of flattened P waves, a prolonged PR interval, widened QRS complexes, and tall or spiked T waves. These fndings indicate the need for emergency treatment to decrease the serum potassium concentration prior to sedation/anesthesia for urethral catheterization. Struvite Uroliths Medical dissolution of feline struvite uroliths is effective; however, the decision to proceed surgically as opposed to medically involves several considerations (Table 1). Diet. Struvite dissolution diets (Table 2) are magnesium-reduced, acidifying diets. Due to their high sodium content and acidifying nature, these diets should not be fed to immature cats; reproducing queens; or cats with CKD, hypertension, congestive heart failure, postrenal azotemia/uremia, or hypokalemia. Additional supplementation of sodium chloride and/or urinary acidifers is not recommended with use of dissolution diets. It is ideal to transition from the normal diet to the dissolution diet over a period of at least 1 week. Reradiograph cats on dissolution diets every 2 to 4 weeks, and feed the diet for a minimum of 30 days after the uroliths are no longer visible radiographically. The rate at which uroliths dissolve is proportional to the surface area of the urolith exposed to the undersaturated urine. Small, sterile struvite uroliths may dissolve in as little as 1 to 2 weeks. 14 Struvite dissolution diets do not dissolve nonstruvite uroliths and are less effective if a persistent UTI is present or the cat is fed anything in addition to the dissolution diet. 14,15 Table 1. Medical Versus Surgical Treatment for Struvite Urolithiasis ADVANTAGES DISADVANTAGES Surgical • Allows defnitive diagnosis of urolith type via quantitative analysis • Allows surgeon to correct any concurrent or predisposing anatomic abnormalities (eg, urachal remnants, urinary bladder polyps) • Enables collection of urinary bladder mucosal samples for bacterial culture if urine yields no growth on culture • Requires anesthesia • Surgery is invasive, with potential for complications • Associated with possible incomplete urolith removal • Often associated with persisting underlying causes; therefore, recurrence is likely and medical management still necessary Medical • Lower initial costs • Noninvasive • Lower complication rate • Total cost similar to that of surgical treatment due to involved follow-up protocol • Follow-up frequently involves urinalyses, bacterial cultures (if uroliths associated with bacterial UTI), and imaging • Considerable owner compliance required for several weeks to months during follow-up • Contraindicated in cats with urolith-induced obstructive uropathy or nonstruvite urolithiasis Table 2. Examples of Feline Struvite Dissolution Diets Hill's Prescription Diet s/d Feline (hillsvet.com) Medi-Cal Veterinary Diets Dissolution Formula (Veterinary Medical Diets, Inc, Guelph, Ontario) Purina Veterinary Diets UR Urinary St/Ox Feline Formula (purinaveterinarydiets.com) Royal Canin Veterinary Diet Urinary SO (royalcanin.com)

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