ACVIM Small Animal Consensus Recommendations on the Treatment and Prevention of Uroliths in Dogs and Cats.

In an age of advancing endoscopic and lithotripsy technologies, the management of urolithiasis poses a unique opportunity to advance compassionate veterinary care, not only for patients with urolithiasis but for those with other urinary diseases as well. The following are consensus-derived, research and experience-supported, patient-centered recommendations for the treatment and prevention of uroliths in dogs and cats utilizing contemporary strategies. Ultimately, we hope that these recommendations will serve as a foundation for ongoing and future clinical research and inspiration for innovative problem solving.

Fasting urinary calcium-to-creatinine and oxalate-to-creatinine ratios in dogs with calcium oxalate urolithiasis and breed-matched controls.

BACKGROUND: Hypercalciuria and hyperoxaluria are risk factors for calcium oxalate (CaOx) urolithiasis, but breed-specific reports of urinary metabolites and their relationship with stone status are lacking. OBJECTIVE: To compare urinary metabolites (calcium and oxalate) and blood ionized calcium (iCa) concentrations between CaOx stone formers and breed-matched stone-free controls for the Miniature Schnauzer, Bichon Frise, and Shih Tzu breeds. ANIMALS: Forty-seven Miniature Schnauzers (23 cases and 24 controls), 27 Bichons Frise (14 cases and 13 controls), and 15 Shih Tzus (7 cases and 8 controls). METHODS: Prospective study. Fasting spot urinary calcium-to-creatinine and oxalate-to-creatinine ratios (UCa/Cr and UOx/Cr, respectively) and blood iCa concentrations were measured and compared between cases and controls within and across breeds. Regression models were used to test the effect of patient and environmental factors on these variables. RESULTS: UCa/Cr was higher in cases than controls for each of the 3 breeds. In addition to stone status, being on a therapeutic food designed to prevent CaOx stone recurrence was associated with higher UCa/Cr. UOx/Cr did not differ between cases and controls for any of the breeds. Blood iCa was higher in cases than controls in the Miniature Schnauzer and Bichon Frise breeds and had a moderate correlation with UCa/Cr. CONCLUSIONS AND CLINICAL IMPORTANCE: Hypercalciuria is associated with CaOx stone status in the Miniature Schnauzer, Bichon Frise, and Shih Tzu breeds. UOx/Cr did not correlate with stone status in these 3 breeds. These findings may influence breed-specific stone prevention recommendations.

The effect of disease on the urinary purine metabolite concentrations in dogs.

This prospective study was designed to determine the urinary concentrations of purine metabolites in healthy and diseased dogs. The goals were to test the hypothesis that urine concentrations of terminal purine metabolites will identify dogs with diseases that disturb purine degradation. Five hundred and sixty-three client-owned dogs admitted sequentially to the veterinary medical centre were included. Dogs were divided into groups on the basis of their disease. Urine concentrations of xanthine, uric acid, allantoin and creatinine were measured by high-pressure liquid chromatography. Xanthine and uric acid to creatinine ratios were significantly increased in dogs with chronic kidney disease (p = 0.01). The uric acid to creatinine ratio was significantly increased in dogs with cancer compared with clinically healthy dogs (p = 0.04), and significantly increased in dogs receiving chemotherapy for their disease (p < 0.01). Compared to clinically healthy dogs, xanthine and uric acid to creatinine ratios were significantly increased in dogs with hyperadrenocorticism (p < 0.01, and 0.04, respectively). Therefore, the results of this study found that the urinary concentrations of purine metabolites in dogs are significantly impacted by systemic disease. Cancer, chronic kidney disease, and hyperadrenocorticism are associated with altered concentrations of urinary purine metabolites in dogs.

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.

Erythropoietin response to hypoxia in patients with diabetic autonomic neuropathy and non-diabetic chronic renal failure.

AIMS: An erythropoietin (EPO)-deficient anaemia is recognized in Type 1 diabetic patients with early nephropathy and symptomatic autonomic neuropathy (DN). The aim of this study was to determine whether the EPO response to hypoxia was deficient in order to clarify the mechanisms involved in this process. METHODS: Five Type 1 diabetic patients DN (age 39 (28-48) years (mean (range))) with EPO-deficient anaemia (haemoglobin, Hb 10.6 (9.5-12.0) g/dl, EPO 5.0 (3.2-6.5) IU/l) and early diabetic nephropathy (persistent proteinuria 1161.6 (130-2835) mg/day, serum creatinine 97.6 (63-123) micromol/l)) were compared with nine normal subjects (age 31 (24-39) years, Hb 13.4 (11.8-15.7) g/dl, EPO 7.6 (5.6-10.3) IU/l) and four patients with non-diabetic advanced chronic renal failure RF (proteinuria 2157.5 (571-4578) mg/day, serum creatinine 490.2 (406-659) micromol/l, Hb 10.3 (9.0-11.3) g/dl, EPO 4.6 (2.9-8.5) IU/l). The subjects were exposed to 6 h of hypoxia (inspired oxygen 11.6-12.6%) by breathing a gas mixture via a hood. Hourly serum EPO levels were measured. RESULTS: All groups showed a rise in EPO production after 2 h. The diabetic DN group achieved a similar maximal response to the normal subjects at 6 h (EPO 17.3 +/-5.4 vs. 17.8 +/-7.9 IU/l). The renal failure patients mounted an EPO response to hypoxia but at lower EPO levels. CONCLUSIONS: Although the DN patients have inappropriately low EPO levels for the severity of their anaemia, they can mount an appropriate EPO response to moderate hypoxia. The mechanism underlying the EPO-deficient anaemia present in some diabetic patients remains unclear.

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.

An integrated epidemiologic and radiographic algorithm for canine urocystolith mineral type prediction.

Research involved 2 databases. One database (occurrence frequency) comprised the age, breed, gender and urocystolith mineral type (pure chemical types only) from 2041 canine patients submitted to the Minnesota Urolith Center. The other database (imaging) comprised the maximum size, surface (rough, smooth, and smooth with blunt tips), shape (faceted, irregular, jackstone, ovoid, and round) and internal architecture (lucent center, random-nonuniform, and uniform) from 434 canine patients imaged in a urinary bladder phantom. The imaging database was a partial subset of the occurrence frequency database. Imaging techniques simulated were survey radiography and double contrast cystography. The databases were compared using multivariate analysis techniques. Equations were developed to use clinically-relevant characteristics (age, breed, gender, maximum size, surface, shape, and internal architecture) to predict urocystolith mineral types. The goal was to assess the accuracy of the various techniques in predicting the urocystolith mineral types. The combination of signalment (age, breed, gender) and simulated survey radiographic findings does not improve mineral type prediction accuracy (average across all mineral types is 69.9%) beyond that achievable with signalment alone (average across all mineral types is 69.8%). However, the combination of signalment and double contrast cystography does improve mineral type prediction accuracy (average across all mineral types is 75.3%). For comparison, mineral type prediction accuracy without signalment from survey radiographs only was 65.7% across all mineral types. The clinical utility of the algorithm is the option to distinguish urocystolith mineral types requiring surgical vs. medical treatment.

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.

Evaluation of urinary carnitine and taurine excretion in 5 cystinuric dogs with carnitine and taurine deficiency.

Five client owned dogs with cystinuria were diagnosed with carnitine and taurine deficiency while participating in a clinical trial that used dietary management of their urolithiasis. Stored 24-hour urine samples collected from the cystinuric dogs before enrollment in the clinical diet trial were quantitatively evaluated for carnitine and taurine. These results were compared to those obtained from 18 healthy Beagles. Both groups of dogs were fed the same maintenance diet for a minimum of 2 weeks before 24-hour urine collection. The protocol used for 24-hour urine collections was the same for cystinuric dogs and healthy Beagles except that cystinuric dogs were catheterized at baseline, 8 hours, 12 hours, and at the end of the collection, whereas Beagles were catheterized at baseline, 8 hours, and at the end of the collection. Three of 5 dogs with cystinuria had increased renal excretion of carnitine. None of the cystinuric dogs had increased renal excretion of taurine, but cystinuric dogs excreted significantly less (P < .05) taurine in their urine than the healthy Beagles. Carnitinuria has not been recognized previously in either humans or dogs with cystinuria, and it may be 1 risk factor for developing carnitine deficiency. Cystinuric dogs in this study were not taurinuric; however, cystine is a precursor amino acid for taurine synthesis. Therefore, cystinuria may be 1 risk factor for developing taurine deficiency in dogs. We suggest that dogs with cystinuria be monitored for carnitine and taurine deficiency or supplemented with carnitine and taurine.

Effects of dietary fat and carnitine on urine carnitine excretion in healthy dogs.

Turnover of carnitine in the body is primarily the result of renal excretion, and high-fat (HF) diets have been shown to increase urine carnitine excretion in healthy people. Recently, increased renal excretion of carnitine was observed in dogs diagnosed with cystinuria and carnitine deficiency. Carnitine deficiency has been linked to dilated cardiomyopathy and lipid storage myopathies in dogs and humans, and low-fat (LF) diets have been beneficial in some human patients with carnitine deficiency. In addition, HF, protein-restricted diets are often recommended for management of cystinuria in dogs. However, whether HF diets increase renal carnitine excretion in dogs or whether dogs with carnitine deficiency would benefit from LF diets remains unknown. Therefore, the purpose of this study was to determine the influence of dietary fat and carnitine on renal carnitine excretion in healthy dogs. Results from this study revealed that an HF diet increased urine carnitine excretion in dogs; however, carnitine excretion with the HF diet was not significantly different from that in dogs consuming an LF diet. Nonetheless, these results raise the possibility that increased renal carnitine excretion associated with HF diets could be one risk factor for development of carnitine deficiency in dogs with an underlying disorder in carnitine metabolism, and some dogs with carnitine deficiency may benefit from an LF diet. Another important observation in this study was that renal excretion of carnitine exceeded dietary intake in all diet groups, confirming previous reports that concluded that canine renal tubular cells reabsorb carnitine poorly when compared with those of humans.

Hyperventilation and asymptomatic chronic asthma.

BACKGROUND: We have consistently argued that mild asthma is an important underlying aetiological factor in patients with severe symptomatic hyperventilation. While hyperventilation has been demonstrated in acute asthma, there have been few studies in mild chronic asthma, and mechanisms are uncertain. METHODS: Twenty three currently asymptomatic chronically asthmatic patients (occasional use of bronchodilators, normal lung function, hyperresponsive to methacholine) were studied and 17 matched normal subjects acted as controls. Ventilation, pattern of breathing, arterial carbon dioxide and oxygen tensions (PaCO(2), PaO(2)), end tidal PCO(2) (PETCO(2)), standard lung function, airway responsiveness to methacholine, airway inflammation assessed by eosinophils in induced sputum, and psychiatric morbidity (Spielberger STAI-Y and Beck Depression Inventory) were measured. RESULTS: Despite the absence of current asthmatic symptoms, no clinical evidence of hyperventilation, and normal lung function in the patients with asthma, PaCO(2) and PETCO(2) were significantly (p<0.01) lower in the patients than in the control group (mean (SD) PaCO(2) 4.96 (0.43) kPa for patients versus 5.27 (0.38) kPa for controls (mean difference 0.31 kPa, 95% confidence interval (CI) 0.06 to 0.56, p<0.02)). PETCO(2) was very similar to PaCO(2) in both groups (mean (SD) PETCO(2) 4.89 (0.47) kPa for the patients and 5.28 (0.40) for the controls (mean difference 0.39 kPa, 95% CI 0.12 to 0.66, p<0.01)). There was no significant difference in ventilation or respiratory pattern between the two groups. The reduced PaCO(2) in the asthmatic patients correlated significantly with the concentration of methacholine provoking a fall in FEV(1) of more than 20% (PC(20)) (r = 0.56, p<0.01) but not with any aspect of lung function, eosinophil count, or anxiety/depression. CONCLUSION: Mild asymptomatic asthma is not associated with clinically significant hyperventilation but is associated with a significant reduction in both arterial and end tidal PCO(2) which relates to airway hyperresponsiveness rather than to the degree of airway obstruction or mucosal inflammation. Anxiety and depression appear not to be implicated.

Relevance of sonographic artifacts observed during in vitro characterization of urocystolith mineral composition.

Nine pure mineral type canine uroliths (bladder or urethral origin only) were imaged ultrasonographically using 3.5 MHz, 5.0 MHz, and 7.5 MHz fixed focus, mechanical sector transducers in a urinary bladder phantom. The uroliths studied were those composed of 100% magnesium ammonium phosphate, calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate appatite, and calcium hydrogen phosphate dihydrate (brushite), ammonium acid urate, sodium acid urate, cystine, and silica. The occurrence of both reverberation/streak and acoustic shadowing artifacts were compared to urocystolith mineral type (classified by effective atomic number), urocystolith width, urocystolith height (thickness), and ultrasonographic imaging frequency. No predictable relationship was found between either of the artifacts seen beyond the urocystolith (reverberation/streak or the acoustic shadowing) and urocystolith mineral type. There was no statistical relationship between the occurrence of reverberation/streak artifact and the size (width or height) of the urocystolith or the ultrasonographic frequency. There was, however, a statistically relevant relationship between ultrasonographic imaging frequency and the occurrence of acoustic shadowing and between urocystolith height (thickness) and the occurrence of acoustic shadowing. However, regardless of ultrasound frequency, acoustic shadowing was observed less than 35% of the time in any of the urocystolith mineral types examined. Based on the imaging of the bladder phantom supporting apparatus (7.0 mm bolts covered by plastic), the accurate characterization of a curved object surface directly facing the transducer was found to be directly related to the frequency of sound used for imaging and at best predictably limited to curved vs flat. Accurate measurement of the maximum transverse dimension of an echogenic curved object or accurate characterization of the lateral borders of such an object was considered unlikely with general ultrasonographic equipment of the frequencies studied. Therefore, detailed architectural characterization of urocystoliths suitable for mineral composition prediction is considered highly unlikely with general pulse-echo ultrasonographic techniques.

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.

Contrast medium-related artifacts observed during in vitro radiographic characterization of urocystolith mineral composition.

Nine pure mineral types of canine uroliths (bladder or urethral origin only) were exposed to sequential increasing concentrations of iodinated, radiographic contrast medium in petri dishes. The uroliths studied were those composed of 100% magnesium ammonium phosphate, calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate appatite, and calcium hydrogen phosphate dihydrate (Brushite), ammonium acid urate, sodium acid urate, cystine, and silica. Two phenomena were observed. First, there was a tendency for selected urocystoliths to undergo radiopacity augmentation beyond that expected for just contrast medium superimposition. This was termed, contrast medium adhesion, which persisted despite repeated washing of the urocystoliths. Second, there was a tendency for bubbles to form on or near selected urocystolith chemical types. These observations prompted careful scrutiny for their occurrence in subsequent clinical simulation of radiographic procedures using these same urocystoliths in a urinary bladder phantom. Imaging techniques simulated were survey radiography, pneumocystography, double contrast cystography (two iodine concentrations). The contrast medium adhesion occurrence found in the petri dish studies was compared to urocystolith mineral type. Similar comparisons were made for contrast medium adhesion occurrence in the bladder phantom. The detection of contrast medium adhesion in the bladder phantom differed from that observed in the petri dish experiments. While contrast adhesion occurred across a fairly broad range of the urocystolith mineral types in the petri dish studies, it was observed primarily for sodium acid urate and cystine urocystoliths in the bladder phantom. Prompted by the observation of bubbles in association with a limited number of urocystolith types in the petri dish studies, bubble occurrence in the bladder phantom was compared to the urocystolith type. Bubble formation on or near the urocystoliths, although uncommonly observed, was seen only with either cystine or silica urocystoliths. The potential clinical utility and clinical caveat aspects of these phenomena are discussed.

Loss of urocystolith architectural clarity during in vivo radiographic simulation versus in vitro visualization.

Urocystoliths of 9 mineral types from 434 canine patients submitted to the University of Minnesota Urolith Bank were imaged in a urinary bladder phantom. Imaging techniques simulated were survey radiography and double contrast cystography. Morphologic characteristics visually observed in vitro or by interpretation of high-resolution specimen radiographs were compared to those seen using the simulated in vivo imaging techniques. Shape characteristics that were accurately detected > or = 25% of the time on simulated survey or double contrast radiography were faceted, irregular, jackstone, ovoid, and round. Surface characteristics that were accurately detected > or = 25% of the time on simulated survey or double contrast radiography were rough, smooth, and smooth with blunt tips. Internal architecture characteristics that were accurately detected > or = 25% of the time on simulated survey or double contrast radiography were lucent center, random-nonuniform, and uniform. Shapes such as bosselated, faceted-ovoid, and rosette; surfaces such as botryoidal, and knife-edged; and internal architecture characteristics such as dense center, dense shell, laminated, and fissures were of almost no value either due to poor detectability or poor accuracy of recognition. Based on optimized simulated survey and double contrast radiographic procedures, it appears that a number of shape, surface, and internal architecture characteristics may be of limited or no value in discriminating among urocystolith mineral types under clinical circumstances. Shapes and surfaces were more accurately characterized by the simulated double contrast technique, but for internal architecture, the simulated survey radiographic technique seemed slightly superior overall.