PREVENTION OF INFECTION-INDUCED STRUVITE UROLITHS
1. Treatment: Control urinary tract infections. Select antibiotics based on urine bacterial culture and susceptibility results. Culture urine during therapy to verify effectiveness of antibiotics.

With additional recurrent infections, antibiotics for 4 weeks, then 1/2 daily doses for 9-12 months, 4-weekly urine cultures.

2. Acidify urine: medication
3. Diet which promotes acidic urine. These have reduced protein, phosphorus and magnesium.
4. Monitoring: Urine culture and urinalysis in 1 month and 3-monthly.

5. X-ray: Every 6 months or sooner if the patient has recurrent urinary tract infection symptoms*.

*excessive vulval licking, urinating in the house, pollakiuria, haematuria etc.

*identify and eradicate anatomic abnormalities (vaginourethrocystoscopy, contrast vaaginourethrocystography and ultrasonography) and functional (urine cortisol to creatinine ratio, serum biochemical and thyroid profiles and neurological exam) risk factors for recurrent infections.

Note 1: struvite crystalluria is insignificant if the dog has negative urine cultures. However this case has bacteria in the urine.

Note 2: Calcium oxalate crystalluria. Collect fresh urine and analyse within 30 minutes. If persistent and in breeds (Bichon Frise, Miniature Schnauzer, Yorkshire Terrier, Shih Tzu, Lhasa Apso), discontinue diets that promote formation of acidic urine and consult recommendations for Calcium oxalate prevention.

An American veterinary school (webpage not available to the members of the public) that does urolith analysis for Hills' samples, recorded that medical dissolution of struvite uroliths with Hills' s/d canine was 100% effective after 3-6 weeks for sterile struvite uroliths and 8-12 weeks with effective antibiotics for infection-induced struvite uroliths. It seems that this institution favours medical treatment (i.e. no surgery to remove stones).

Immature dogs should not be given low protein s/d for a long term. However, a short-term use with antibiotics has rapidly dissolved infection-induced struvite uroliths in 9-12 days without adverse events.

Owner/patient compliance when feeding s/d is easily determined with a urine SG (mean = 1.008+/-0.003) and pH (mean =6.2+/-0.7). If no urine sample, serum urea nitrogen is a reliable marker (mean 3.5+/- 2.4 mg/dl). The s/d diet is high in fat and high fat is a risk factor for pancreatitis.

Female Miniature Schnauzers and others with hyperadrenocortisicism risk pancreatitiis and UTI that includes urease-producing uropathogens. Respond by discontinuing s/d diet, maintain hydration if vomiting/pancreatitis occur. Consider alternative that also acidify urine eg. canned w/d Canine) to correct both diseases. 26% of canine nephroliths are composed of struvite. They can be dissolved medically as in bladder stones but this takes a much longer time due to reduced kidney function, reduced urine production and reduced nephrolith dwell time in therapeutically undersaturated urine.

CONCLUSION.
Approaches to treatment. Medical or surgical treatment? For large stones and urethral obstruction, I advise surgery to remove all the stones after antibiotic treatment. Stones do recur even after complete stone removal in some cases. Many Singapore owners do not comply with medical treatment and the follow-up reviews (urine tests 3-monthly, X-rays 6 monthly). I presume it is due to economics and lack of time.  Surgery should be done only after effective antibiotic treatment rather than immediately.

In this case, the pug drinks little but drinks more after going outdoors for exercise. "Try adding some ice-cubes to the water," I said to the lady who loves pugs only. Regular urine monitoring will be needed for the next 6 months and no dry dog food or dog treats and biscuits must be given. The lady owner was satisfied with the outcome that the pug was no longer taking a long time to pee.

Urine-marking in male dogs may or may not lead to urinary tract infections as the male dog with-holds urine to have sufficient amount to mark the territory.  The alpha male dog pees until the last drop and even tries to pee when there is no more urine in the bladder.  Neutering the dog may help prevent urinary tract infection. The lady owner was not keen on neutering.