Page 817 - Small Animal Clinical Nutrition 5th Edition

Canine Purine Urolithiasis 847

ed in purines and that promote formation of less concentrated urine ammonium concentration following surgical correction of
VetBooks.ir alkaline urine should be considered (Table 39-6). In one study anomalous shunts would result in spontaneous dissolution of
uroliths composed primarily of ammonium urate.
of naturally occurring ammonium urate urocystoliths in
Additional clinical studies are needed to evaluate the relative
Dalmatian dogs, a low-protein, nonacidifying moist commer-
b
cial veterinary therapeutic food reduced urolith recurrence by value of litholytic foods, allopurinol and/or alkalinization of
50% compared with an adult moist maintenance food (Lulich urine in dissolving ammonium urate uroliths in dogs and cats
et al, 1998). If dry foods are fed, water should be added with the with portal vascular anomalies. The likelihood of adverse side
goal of maintaining a urine specific gravity less than approxi- effects or further deterioration in hepatic function following
mately 1.025. administration of allopurinol to dogs with portal vascular
If urate crystalluria or hyperuricuria persists, serial urinary anomalies has apparently not been determined. Reversible hep-
pH measurements are indicated to ensure appropriate alkalin- atitis has been reported to be an uncommon reaction to allop-
ization. If necessary, urine alkalinizing agents may be added to urinol given to people (Al-Kawas et al, 1981; Murrell and
the protocol. If difficulties persist, low doses of allopurinol Rapeport, 1986; Nelson and Elion, 1984). Pending further
(approximately 10 to 20 mg/kg body weight/day) may be given study, appropriate precautions should be taken to monitor
cautiously. Prolonged administration of high doses (30 mg/kg patients for adverse reactions if allopurinol is given to dogs with
body weight/day) of allopurinol may result in formation of xan- portal vascular anomalies. Because tetracycline exacerbates
thine uroliths (Bartges et al, 1992; Ling, 1995).The risk of xan- hepatic and renal dysfunction in dogs with experimentally pro-
thine urolithiasis is enhanced if dietary purines are not restrict- duced portal vascular anomalies, it should not be routinely used
ed during allopurinol therapy.Therefore, appropriate caution in to treat UTIs in dogs with naturally occurring portal vascular
long-term administration of this drug is indicated. Because it is anomalies (Faraj et al, 1982).
possible to induce dissolution of recurrent ammonium urate
uroliths, it is unnecessary to risk the use of prophylactic proto- ENDNOTES
cols that may themselves cause disorders.
When considering use of foods to minimize occurrence of a. Prescription Diet k/d Canine. Hill’s Pet Nutrition, Inc.,
urolithiasis, avoid an “always” or “never” approach. The final Topeka, KS, USA.
decision should be based on the overall balance of benefits to b. Prescription Diet u/d Canine. Hill’s Pet Nutrition, Inc.,
the patient and associated risks. Topeka, KS, USA.
c. Zyloprim. Glaxo Wellcome, Research Triangle Park, NC,
Non-Dalmatian Dogs USA.
We did not find any published information concerning recur- d. Urocit-K. Mission Pharmacal, San Antonio, TX, USA.
rence rates of urate uroliths in non-Dalmatian dogs; however, e. Polycitra-K. Willen Drug Co., Baltimore, MD, USA.
recurrence of urate uroliths was observed in three of five
English bulldogs. Therefore, preventive measures should also
be considered for non-Dalmatian dogs. REFERENCES
There have been few studies of the biologic behavior of
ammonium urate uroliths in dogs and cats with portal vascular The references for Chapter 39 can be found at
anomalies and/or microvascular dysplasia. It is logical to hy- www.markmorris.org.
pothesize that elimination of hyperuricuria and reduction of