Page 2040 - Cote clinical veterinary advisor dogs and cats 4th

1020 Urolithiasis, Urate

can lead to azotemia, hyperkalemia, and ○ Cystoscopic-assisted retrieval (p. 1085) Recommended Monitoring
metabolic acidosis. ○ Cystotomy/urethrotomy/urethrostomy/ • Serum biochemical profile and urinalysis 2
VetBooks.ir sometimes identified; physical irritation and/ Chronic Treatment 7.0-8.0, specific gravity < 1.020, and absent
pyelotomy/nephrotomy
weeks after diet change. Goal is urine pH
• Urinalysis: frequently aciduria; urate crystals
○ Lithotripsy
or secondary infection sometimes leads to
crystals. Assuming adequate renal function
hematuria, pyuria, or bacteriuria
• Urine culture and sensitivity to rule out • Animals with hepatic disease and diet adherence, blood urea nitrogen
(BUN) should be < 10 mg/dL. Monitor
secondary infection ○ Surgical correction of PSS prevents recur- urinalysis q 2-4 weeks until uroliths resolved
• Abdominal radiographs: urate uroliths are rence; cystotomy may be used to remove and q 3-6 months thereafter.
often radiolucent (radiopacity: struvite ≥ uroliths during surgical correction of • Monitor dissolution of uroliths q 4 weeks
oxalate = CaPO 4 = silica > cystine > urate). hepatic shunt. with lower urinary tract contrast studies or
○ If visible, often few smooth, round uroliths ○ If hepatic disease cannot be corrected, ultrasound. Monitor for recurrence in like
identified institute medical management (including manner q 3-6 months for a year, then q
• Microhepatica is suggestive of PSS, MVD, restricted-protein diet), and monitor for 6-12 months.
or cirrhosis. recurrence.
• Abdominal ultrasound: confirm urolithiasis, ○ Allopurinol, which inhibits the conversion PROGNOSIS & OUTCOME
which may be missed on abdominal radio- of xanthine to uric acid, is ineffective with
graphs. Confirms location of uroliths within PSS or MVD. • Prognosis for dissolution: fair (dogs)
the urinary tract; may identify PSS or hepatic • Promote water consumption to avoid con- • Recurrence is common unless cause resolved
abnormalities centrated urine (e.g., canned food, wetting (e.g., PSS corrected).
dry food, use of cat water fountains).
Advanced or Confirmatory Testing • Feed low-purine calculolytic diet (see PEARLS & CONSIDERATIONS
• In non-Dalmatians or when appropriate: Nutrition/Diet below).
serum bile acids or other tests to rule out • If urine remains acidic after diet change, con- Comments
hepatic disease sider adding sodium bicarbonate 25-50 mg/ • Non-Dalmatian dogs with urate uroliths
• Contrast (or double-contrast) cystography, kg PO q 12h or potassium citrate 75 mg/ should be evaluated for hepatic disease, even
urethrography: alternative to ultrasound kg PO q 12-24h, with dosage adjustment when showing no overt signs of hepatopathy.
for confirmation/localization of radiolucent to maintain urine pH of 7.0-7.5. • Cats with urate urolithiasis have underlying
stones (p. 1181) • Allopurinol 15 mg/kg PO q 12h, with hepatic disease less commonly than non-
• Urolith analysis: retrieved stones submitted dosage reduction for azotemic dogs, for Dalmatian dogs.
for quantitative analysis (crystallography, dissolution • Apparently healthy dogs > 5 years of age
x-ray diffraction, infrared spectroscopy) to • Medical dissolution is not effective in all with congenital PSS often develop clinical
determine urolith type dogs. For one-third, urate uroliths resolve in signs of urate urolithiasis rather than signs
• Cystoscopy may facilitate urolith removal approximately 30 days. For another one-third of hepatic encephalopathy.
for analysis and therapy (p. 1085). of dogs, uroliths decrease in size and number,
facilitating urolith retrieval by voiding Prevention
TREATMENT urohydropropulsion or catheter-assisted • Avoid high-protein diets in at-risk dogs (e.g.,
retrieval. For the other one-third of dogs, Dalmatian), but severely protein-restricted
Treatment Overview uroliths increase in size and number due to diets or allopurinol before a first episode of
Urinary tract obstruction requires immediate xanthine formation. urate urolithiasis is not recommended.
relief. In the absence of urinary obstruction, • Heritability of tendency to form urate
treatment consists of medical stone dissolu- Nutrition/Diet uroliths suggests breeding affected Dalmatian
tion or manual removal of stones, as well Reduced-protein (therefore reduced-purine) should be avoided.
as treatment of underlying disorders (e.g., diet: • Long-term dietary ± allopurinol therapy
PSS) or preventive therapy. Medical dis- • Dogs: for example, Hills u/d, Royal Canin 5-7 mg/kg PO q 12h is indicated for
solution often is ineffective in dogs and cats Urinary UC Low Purine, Royal Canin Dalmatian after first episode of urolithiasis.
with PSS. Vegetarian Formula
• Cats: a diet formulated for chronic kidney Technician Tips
Acute General Treatment disease, such as Prescription Diet k/d, Royal Dalmatian owners should be aware of this
• Relieve urinary tract obstruction (pp. 1175 Canin Renal Support (A, D, E, F, S, or T) common issue in the breed.
and 1176) if present. Purina NF, Blue Buffalo KM
• If present, treat hepatic encephalopathy • With PSS and MVD: a diet formulated for Client Education
(p. 440). liver disease such as Prescription Diet l/d or • Urethral obstruction is life-threatening. Stran-
• If present, treat urinary tract infection Royal Canin Hepatic LS guria should prompt immediate veterinary
(pp. 232 and 849). attention.
• Choose between medical dissolution (see Drug Interactions • Adherence to dietary therapy must be strict.
Chronic Treatment below) and mechanical Allopurinol may result in skin eruptions when • Implications for heritability in Dalmatians
removal: used with ampicillin/amoxicillin. should be addressed.
○ Urinary tract obstruction should be • After Dalmatians have formed urate uroliths,
relieved mechanically. Possible Complications preventive therapy should continue lifelong.
○ Mechanical removal allows for urolith • Chronic use of low-purine diets may result in
analysis, culture. cardiomyopathy, perhaps related to carnitine SUGGESTED READING
○ Cats are poorly amenable to medical or taurine deficiency (especially English Lulich JP, et al: ACVIM Small Animal Consensus
dissolution of urate uroliths. bulldogs). Recommendations on the Treatment and Prevention
• Mechanical removal of calculi (pp. 1175 and • Severely protein-restricted diets are inap- of Uroliths in Dogs and Cats. J Vet Intern Med
1176) propriate for growing, pregnant, or lactating 30:1564-1574, 2016.
○ Urohydropropulsion (voiding, retrograde): animals. AUTHORS: Joseph W. Bartges, DVM, PhD, DACVIM,
avoid in male cats • Xanthine urolith formation with allopurinol DACVN; Leah A. Cohn, DVM, PhD, DACVIM
○ Catheter-assisted retrieval administration EDITOR: Leah A. Cohn, DVM, PhD, DACVIM
www.ExpertConsult.com