Recent shifts in the global proportions of canine uroliths.

Epidemiological surveys are important tools to identify emerging trends in disease. The Minnesota Urolith Centre has been tracking the occurrence of uroliths for over 30 years. To evaluate global changes in the frequencies of canine uroliths, submissions to the Minnesota Urolith Centre in 1999 and 2000 (n = 39,965) were compared with submissions in 2009 and 2010 (n = 99,598). The proportion of calcium oxalate uroliths rose on every continent except in Europe. Seventy-five per cent of dogs with calcium oxalate uroliths were between 5 and 11 years old. The proportion of struvite uroliths decreased on every continent except in Australia-Oceania. Seventy-seven per cent of all struvite formers were between two and eight years old. The proportion of purine uroliths has declined slightly. Worldwide, uroliths composed of cystine, calcium phosphate, calcium phosphate carbonate and silica remain uncommon. Epidemiological studies of urolithiasis are essential for constructing effective experimental designs and selecting appropriate cases and controls to conduct clinical trials with meaningful results.

Association between dietary factors and calcium oxalate and magnesium ammonium phosphate urolithiasis in cats.

OBJECTIVE: To identify dietary factors associated with the increase in occurrence of calcium oxalate (CaOx) uroliths and the decrease in occurrence of magnesium ammonium phosphate (MAP) uroliths in cats. DESIGN: Case-control study. ANIMALS: 173 cats with CaOx uroliths, 290 cats with MAP uroliths, and 827 cats without any urinary tract diseases. PROCEDURE: Univariate and multivariate logistic regression were performed. RESULTS: Cats fed diets low in sodium or potassium or formulated to maximize urine acidity had an increased risk of developing CaOx uroliths but a decreased risk of developing MAP uroliths. Additionally, compared with the lowest contents, diets with the highest moisture or protein contents and with moderate magnesium, phosphorus, or calcium contents were associated with decreased risk of CaOx urolith formation. In contrast, diets with moderate fat or carbohydrate contents were associated with increased risk of CaOx urolith formation. Diets with the highest magnesium, phosphorus, calcium, chloride, or fiber contents and moderate protein content were associated with increased risk of MAP urolith formation. On the other hand, diets with the highest fat content were associated with decreased risk of MAP urolith formation. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that diets formulated to contain higher protein, sodium, potassium, moisture, calcium, phosphorus, and magnesium contents and with decreased urine acidifying potential may minimize formation of CaOx uroliths in cats. Diets formulated to contain higher fat content and lower protein and potassium contents and with increased urine acidifying potential may minimize formation of MAP uroliths.

Effects of hydrochlorothiazide and diet in dogs with calcium oxalate urolithiasis.

OBJECTIVE: To determine whether hydrochlorothiazide (HCTZ) reduces urinary calcium excretion in dogs with calcium oxalate urolithiasis. DESIGN: Original study. ANIMALS: 8 dogs with calcium oxalate urolithiasis. PROCEDURE: 4 treatment protocols were evaluated in each dog (a low calcium, low protein diet designed to prevent calcium oxalate urolith formation with and without administration of HCTZ [2 mg/kg (0.9 mg/lb) of body weight, PO, q 12 h] and a maintenance diet with higher quantities of protein and calcium with and without administration of HCTZ). At the end of each 2-week treatment period, 24-hour urine samples were collected. Blood samples were collected during the midpoint of each urine collection period. Analysis of variance was performed to evaluate the effects of HCTZ and diet on urine and serum analytes. RESULTS: Hydrochlorothiazide significantly decreased urine calcium and potassium concentration and excretion. Hydrochlorothiazide also significantly decreased serum potassium concentration. Compared with the maintenance diet, the urolith prevention diet significantly decreased urine calcium and oxalic acid concentration and excretion. Dogs consuming the urolith prevention diet had significantly lower serum concentrations of albumin and urea nitrogen. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of HCTZ decreased urine calcium excretion in dogs with a history of calcium oxalate urolith formation. The greatest reduction in urine calcium concentration and excretion was achieved when dogs received HCTZ and the urolith prevention diet. Results of this study suggest that the hypocalciuric effect of HCTZ will minimize recurrence of calcium oxalate urolith formation in dogs; however, long-term controlled clinical trials are needed to confirm the safety and effectiveness of HCTZ.

Epidemiologic study of risk factors for lower urinary tract diseases in cats.

OBJECTIVE: To determine proportional morbidity rates (PMR) and risk factors for lower urinary tract diseases (LUTD) in cats. DESIGN: Case-control study. SAMPLE POPULATION: Records of 22,908 cats with LUTD and 263,168 cats without LUTD. PROCEDURE: Data were retrieved from the Purdue Veterinary Medical Data Base. Descriptive statistics and univariate logistic regression analyses were performed to assess whether breed, age, sex, and neutering status were associated with different causes of LUTD. RESULTS: Mean PMR for LUTD irrespective of cause was 8/100 cats (range, 2 to 13/100 cats). Increased risk for urocystolithiasis (Russian Blue, Himalayan, and Persian cats), bacterial urinary tract infections (UTI; Abyssinian cats), congenital urinary tract defects (Manx and Persian cats), and urinary incontinence (Manx cats) was detected. Cats between 2 and < 7 years of age had increased risk for urethral plugs, neurogenic disorders, congenital defects, and iatrogenic injuries. Cats between 4 and < 10 years of age had increased risk for urocystolithiasis, urethral obstructions, and idiopathic LUTD. Cats > or = 10 years of age had increased risk for UTI and neoplasia. Castrated males had increased risk for each cause of LUTD except UTI and incontinence. Spayed females had increased risk for urocystolithiasis, UTI, and neoplasia. Sexually intact females had decreased risk for each cause of LUTD except neurogenic disorders and iatrogenic injuries. CONCLUSION AND CLINICAL RELEVANCE: Specific breed, age, sex, and neutering status may be associated with specific types of feline LUTD. Knowledge of patient risk factors for LUTD may facilitate development of surveillance strategies that enhance earlier detection.

Patient and environmental factors associated with calcium oxalate urolithiasis in dogs.

OBJECTIVE: To test the hypothesis that breed, age, sex, body condition, and environment are risk factors for development of calcium oxalate uroliths in dogs. DESIGN: Case-control study. ANIMALS: 1,074 dogs that formed calcium oxalate uroliths and 1,724 control dogs that did not have uroliths. PROCEDURE: A validated multiple-choice questionnaire was designed to collect information from veterinarians and owners within 1 year of the date of urolith detection concerning signalment and environment of the dogs. Univariate and multivariate analyses were performed to calculate odds ratios to assess whether breed, age, sex, body condition, and environment were risk factors for calcium oxalate urolith formation. RESULTS: Middle-aged (8- to 12-year-old) castrated male dogs had increased risk for formation of calcium oxalate uroliths. Urolith formation was also associated with increasing age. Dogs of certain breeds, including Miniature and Standard Schnauzer, Lhasa Apso, Yorkshire Terrier, Bichon Frise, Shih Tzu, and Miniature and Toy Poodle, had increased risk for developing calcium oxalate uroliths. Overweight dogs also had increased risk. CONCLUSIONS AND CLINICAL RELEVANCE: Knowledge of patient and environmental risk factors for development of calcium oxalate uroliths may facilitate development of surveillance strategies that result in earlier detection of this disease. Modification of environmental factors and body weight may minimize calcium oxalate urolith formation and recurrence.

Association between patient-related factors and risk of calcium oxalate and magnesium ammonium phosphate urolithiasis in cats.

OBJECTIVE: To determine whether breed, age, sex, or reproductive status (i.e., neutered versus sexually intact) was associated with the apparent increase in prevalence of calcium oxalate (CaOx) uroliths and the decrease in prevalence of magnesium ammonium phosphate (MAP) uroliths in cats over time. DESIGN: Case-control study. ANIMALS: Case cats consisted of cats with CaOx (n = 7,895) or MAP (7,334) uroliths evaluated at the Minnesota Urolith Center between 1981 and 1997. Control cats consisted of cats without urinary tract disease admitted to veterinary teaching hospitals in the United States and Canada during the same period (150,482). PROCEDURE: Univariate and multivariate logistic regression were performed. RESULTS: British Shorthair, Exotic Shorthair, Foreign Shorthair, Havana Brown, Himalayan, Persian, Ragdoll, and Scottish Fold cats had an increased risk of developing CaOx uroliths, as did male cats and neutered cats. Chartreux, domestic shorthair, Foreign Shorthair, Himalayan, Oriental Shorthair, and Ragdoll cats had an increased risk of developing MAP uroliths, as did female cats and neutered cats. Cats with CaOx uroliths were significantly older than cats with MAP uroliths. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that changes in breed, age, sex, or reproductive status did not contribute to the apparent reciprocal relationship between prevalences of CaOx and MAP uroliths in cats during a 17-year period. However, cats of particular breeds, ages, sex, and reproductive status had an increased risk of developing CaOx and MAP uroliths.

Epidemiology of canine calcium oxalate uroliths. Identifying risk factors.

Calcium oxalate uroliths are most commonly encountered in Miniature Schnauzers, Lhaso Apsos, Yorkshire Terriers, Bichons Frises, Shih Tzus, and Miniature Poodles. They are more common in males than females, and more common in older than young dogs. Dogs that form abnormal nephrocalcin are also predisposed to calcium oxalate uroliths. Dietary risk factors for calcium oxalate uroliths include excessive calcium supplementation or excessive calcium restriction, excessive oxalic acid, high protein, high sodium, restricted phosphorus, restricted potassium, and restricted moisture (dry formulations). Dogs with hyperadrenocorticism or hypercalcemia are predisposed to calcium oxalate urolith formation.

Canine calcium oxalate urolithiasis. Case-based applications of therapeutic principles.

The case study presented here illustrates the diagnosis and management of calcium oxalate urolithiasis in a Bichon Frise, a breed at increased risk for this type of stone. If the Bichon Frise had persistent hypercalcemia, we would have evaluated serum concentrations of ionized calcium, parathyroid hormone, and vitamin D to identify an underlying cause. Because his urine was alkaline, additional potassium citrate was not provided. Likewise, as a fortified diet was fed to him, vitamin B6 therapy was not considered. This case study illustrates the benefits of radiographic evaluation immediately following surgery and during follow-up examinations. If we had postponed radiographs until the patient developed clinical signs, additional surgical procedures may have been required.