Page 194 - Problem-Based Feline Medicine

186 PART 4 CAT WITH URINARY TRACT SIGNS

owner’s wishes will all influence which procedure is pH should stay below 6.5 long term. Cats passing
most appropriate. alkaline urine should be recultured.
● Surgical removal.
Struvite urolithiasis.
– Cystotomy is performed via a ventral midline
● An acidifying, low-magnesium, low-phosphorus
abdominal approach. An avascular area near the
and low-calcium diet is recommended.
apex of the bladder is selected, stay sutures (3-0
● Alternatively, urine acidifiers (ammonium chlo-
silk) placed on either side of the intended inci-
ride or DL methionine) to effect (approximately
sion line and the bladder is emptied by cysto-
1000 mg/cat/day) can be given orally at mealtime
centesis. A 2-cm incision is made into the
to ameliorate the postprandial alkaline tide. Acute
bladder wall and the uroliths removed. Before
toxicity with high doses cat occur, especially in
closure of the bladder, a urinary catheter
kittens.
attached to a saline-filled syringe is used to flush
● Chronic metabolic acidemia due to long-term acid-
out any uroliths in the bladder neck and urethra.
ification can have adverse effects.
● Medical dissolution.
– Only nephroliths and cystoliths can be med- Calcium oxalate urolithiasis.
ically dissolved. Medical dissolution of uroliths ● A non-acidifying regular diet is recommended.
in the ureters or urethra should not be ● Diets used to prevent struvite urolithiasis should not
attempted. be used.
– Calcium oxalate uroliths can not be medically ● If the diet does not maintain the urine pH above
dissolved. 7.5, potassium citrate (50–75 mg/kg orally 12
– Struvite uroliths can be medically dissolved. hourly) therapy may be used. Monitor total CO to
2
– Mineral composition of the urolith should be ensure alkalosis does not occur. Keep TCO about
2
determined before dissolution therapy is 20 mmol(mEq)/L.
attempted. However, this is often not possible, ● Vitamin B6 (2 mg/kg orally every 24–48 hours)
and crystals in the urine sediment are used as a may be useful.
guide. ● The cause of hypercalcemia, if present, should be
– Dissolution diets are designed to produce an determined and treated.
acidic, low-mineral, dilute urine environment in ● Thiazide diuretics (chlorthiazide, 10 mg/kg orally
which cystic struvite uroliths dissolve over a 12 hourly) with potassium supplementation have
period of 4–8 weeks. Nephroliths usually take been used in normocalcemic dogs with oxalate
longer to dissolve. uroliths.
– The dissolution diet should be fed for at least
Urate urolithiasis.
2–4 weeks after uroliths are no longer visible
● Avoid acidifying diets and diets high in purine pre-
radiographically or on ultrasound.
cursors (e.g. liver).
– Failure to dissolve the uroliths may be due to
poor owner compliance, the presence of urinary Cystine urolithiasis.
tract infection or the mineral composition of the ● Acidifying diets should not be fed.
urolith is not struvite.
Prognosis
Prevention
Recurrence rates of 19% and 37% have been reported.
Long-term prevention strategies to prevent or minimize
reoccurrence should be based on mineral composition Prognosis is guarded because in some cases recur-
of the urolith. rences occur despite the implementation of adequate
preventative measures.
If infection is present, this must be treated and the urine
(culture, urinalysis especially pH) monitored long term Unless preventative measures are implemented,
to ensure that the infection has been eliminated. Urine urolithiasis will reoccur.