Page 941 - Small Animal Clinical Nutrition 5th Edition

Feline Lower Urinary Tract Diseases 973

tent with both urolith types. Findings consistent with struvite
uroliths in this cat include female gender, presence of struvite
VetBooks.ir crystalluria and round, radiopaque uroliths whereas the age

and urinary pH could occur with calcium oxalate uroliths. A
definitive diagnosis requires quantitative urolith analysis,
which is particularly helpful when there are mixed or com-
pound uroliths. For this cat, one option would be to attempt
nutritional dissolution therapy for four weeks; if the uroliths
decrease in size or disappear, struvite urolithiasis is likely and
treatment should be continued. If the uroliths do not decrease
in size or they become larger, other treatment (e.g., physical
removal of uroliths) is indicated because the uroliths are likely
composed of another mineral type.
2. At this time, the most common treatments for managing
cats with struvite uroliths are surgical removal via cystotomy
and medical dissolution with nutritional management. The
choice between these options may depend on the clinician’s
preference and expertise as well as the pet owner’s prefer- Figure 1. Lateral abdominal radiograph reveals two radiopaque
ences. Many veterinarians prefer to surgically remove uroliths in the urinary bladder.
uroliths because they believe that surgical management is
more effective, controls clinical signs quicker and will not be associated with urethral obstruction as uroliths decrease in size,
especially in male cats. However, effectiveness of surgical removal of uroliths has not been critically evaluated in cats. A retro-
spective study including 20 cats with urinary bladder uroliths revealed that five cats (20%) had incomplete removal of uroliths
by cystotomy in a veterinary teaching hospital. In the absence of appropriate studies, it should not be assumed that surgical
management of uroliths is 100% effective. In addition, there have been no reported studies documenting the time required for
resolution of clinical signs after surgical removal of uroliths or that urethral obstruction does or does not occur postoperatively.
Medical management using dissolution foods a,b has been evaluated in two studies of cats with struvite uroliths.The mean time
required for urolith dissolution was around four weeks; however, some cats had radiographic resolution of uroliths two weeks after
beginning nutritional management. Urethral obstruction has not been reported to occur in male cats with struvite uroliths that
were dissolved with nutritional management. In most cats, clinical signs are no longer evident within two weeks of beginning
dissolution foods.
In summary, when selecting treatment for cats with struvite uroliths it may help to ask and answer the following questions: 1)
Which treatment is the least invasive?, 2) Which treatment would I prefer if I had uroliths? and 3) Which treatment is the most
effective based on currently published evidence?
3. After dissolution or removal of struvite uroliths, nutritional management is indicated to decrease risk of urolith recurrence. Based
on current evidence, foods used for prevention of struvite disease should avoid excessive protein, magnesium, phosphorus and
sodium and should maintain a mildly acidic urinary pH. Cats eating struvite preventive foods should be monitored periodically
for urinary pH values and evidence of crystalluria.The goal of treatment is to prevent occurrence of struvite crystalluria and main-
tain urinary pH ≤ 6.4.

Progress Notes
After considering treatment options and the owner’s preferences, the veterinarian recommended a struvite dissolution fooda for this
patient. The daily caloric requirement was calculated and divided into two meals. It was recommended that the patient return in
two weeks for reevaluation to include physical examination, urinalysis and abdominal radiographs. During the first followup exam-
ination two weeks later, the patient was eating the prescribed food exclusively. Analysis of urine collected by cystocentesis revealed
specific gravity = 1.034, pH = 6.0 and mild hematuria (7 RBCs/hpf); there was no pyuria, crystalluria or bacteriuria. Survey abdom-
inal radiographs confirmed that uroliths were smaller (Figure 2); therefore, nutritional management was continued. Radiographic
evaluation performed four weeks after initiation of the dissolution food revealed no visible uroliths (Figure 3).The dissolution food
was prescribed for an additional month after which it was recommended that the patient be transitioned to a maintenance food
with reduced magnesium and phosphorus to prevent struvite urolith recurrence.

Endnotes
a. Prescription Diet s/d Feline, Hill’s Pet Nutrition, Inc., Topeka, KS, USA.
b. Dissolution Formula, Medi-Cal Royal Canin, Guelph, ON, Canada.