Structure and composition of canine urinary calculi

The chemical constituents of 171 specimens of canine urinary calculi have been analysed by infrared spectroscopy. The analysis revealed that 46 per cent of the total contained struvite as the major component; 26 per cent contained cystine; 16 per cent were found to be composed of whewellite and, or, weddellite; 8 per cent of urates; 3 per cent of calcium phosphate (apatite and, or, brushite) and 1 per cent of silica. A series of selected samples was also studied by scanning electron microscopy and energy dispersive X-ray analysis (EDAX). This examination revealed structures similar to human stones. Potassium and complex urates containing two or more cations were commonly found in many areas of ammonium urate and sodium urate calculi. Moreover, EDAX analysis detected a calcium enriched urate in several zones of urate calculi.     

Relationship of nutritional factors to the cause, dissolution, and prevention of feline uroliths and urethral plugs

Feline lower urinary tract disease is often associated with uroliths and urethral plugs. Uroliths and urethral plugs are composed of variable quantities of matrix and a variety of minerals (including struvite, calcium oxalate, ammonium urate, calcium phosphate, and cystine). Knowledge of nutritional factors associated with the pathophysiology of uroliths and urethral plugs facilitates the modification of diets for the dissolution of several minerals contained within them.     

Study of cystine urinary calculi in dogs.

The composition and structure of 48 canine cystine urinary stones were determined by infrared spectroscopy, scanning electron microscopy and electron dispersive X-ray analysis. The infrared analysis showed that about 45% of the specimens were composed of pure cystine. The remainder also contained calcium oxalate (mono and/or dihydrate), magnesium ammonium phosphate hexadydrate (struvite), calcium hydrogen phosphate dihydrate (brushite) and complex urates (ammonium, ammonium potassium and/or potassium enriched ammonium urate). The infrared study of several samples heated at 620 degrees C and 750 degrees C revealed the presence of apatitic calcium phosphate. This compound was difficult to detect in the spectrum of the original samples due to the small proportion of phosphate contained in the calculi and to band overlapping. The examination of a series of selected samples by means of scanning electron microscopy and energy dispersive X-ray analysis complemented the infrared results.     

Feline struvite urolithiasis: factors affecting urine pH may be more important than magnesium levels in food

Eighteen male cats were fed either a canned complete diet or a commercially available dry pelleted diet or the same dry diet containing 1.6 per cent ammonium chloride. The daily food and water intake of four of these cats was measured. Urine samples were taken at random and the pH and the presence of struvite crystals in their sediment estimated. In some samples in which the pH was less than 7.0, and struvite crystals were absent, the pH was increased to 7.0 and any sediment was examined for struvite. No spontaneous struvite was seen in urine samples (pH 5.8) from cats fed the canned complete diet but when its pH was raised to 7.0, 46 per cent of these samples showed struvite. Cats fed the dry pelleted diet had urine of higher pH (7.55) and 78 per cent of the samples contained struvite crystals. Cats fed this diet supplemented with ammonium chloride had a urine pH of 5.97 and only 9 per cent contained struvite crystals but when the pH was adjusted to 7.0 all the samples showed struvite crystals. Energy intake was similar on all three diets but the intake of dry matter was greater on the dry diets. Liquid water intake was greater on the dry diets but total water intake was greatest on the canned complete diet. The intake of magnesium, calcium and phosphate was greater on the dry diets. It is concluded that urine pH is a more important controller of struvite precipitation than mineral intake.     

A survey of urolithiasis in cats

The incidence of urolithiasis in cats is 0.6 per cent. A total of 41 calculi were subjected to epidemiological and analytical investigation. Calculus formation is most frequent in male castrates and occurs exclusively in the bladder and urethra. Eighty per cent of the animals under investigation were overweight and the same percentage required surgical or instrumental treatment. Thirty-seven per cent of the calculi were recurrent, but only 22 per cent were accompanied by an infection. A predisposition due to diet (dry food/tinned food) was not established. Over 75 per cent of the calculi which were analysed consisted of struvite, the formation of which is promoted by an increased pH-value, as well as by a high level of magnesium and phosphate in the urine. The crystalline structure of the calculi indicates a slow growth rate not influenced by an acute infection. The genesis of struvite urolithiasis in cats, as well as measures to prevent its recurrence, are explained.     

Comparison of three techniques for the diagnosis of urinary tract infections in dogs with urolithiasis

OBJECTIVES: To identify an appropriate sampling technique(s) to accurately detect the bacteria causing urinary tract infections in dogs with urolithiasis. METHODS: Twenty-one dogs with urolithiasis were included in the study. Three types of samples were taken from each dog. Urine was collected by cystocentesis, and a urinary bladder mucosal biopsy and urolith were retrieved during cystotomy. The samples were then cultured on blood agar and MacConkey's agar to identify the bacteria associated with urinary tract infections. RESULTS: Bacterial urinary tract infection was found in 16 cases (76.19 per cent). The most prevalent bacteria found to cause urinary tract infection were Escherichia coli (n=7), followed by coagulase-positive Staphylococcus species (n=4), Klebsiella pneumoniae (n=2), Pseudomonas aeruginosa (n=2) and Proteus mirabilis (n=1). In the case of a positive urine culture, the same bacteria were also cultured from the urinary bladder mucosal biopsy alone or from both the urinary bladder mucosal biopsy and urolith. However, in the case of a negative urine culture, bacteria were found to be present in the urinary bladder mucosal biopsy or urolith cultures in 23.81 per cent of dogs. The uroliths that gave positive culture results were either infection-induced uroliths composed of struvite and calcium carbonate phosphate, ammonium acid urate only or metabolic uroliths composed of calcium oxalate and calcium phosphate, or calcium phosphate only. All the uroliths that gave negative culture results were metabolic uroliths composed of calcium oxalate and/or calcium phosphate, and uric acid and calcium phosphate. CLINICAL SIGNIFICANCE: When the culture from the urine obtained by cystocentesis is negative, cultures of urinary bladder mucosal biopsy and urolith are recommended in dogs with urolithiasis in order to accurately assess the microbiological status of the urinary tract.     

Diagnosis and surgical management of ureteral calculi in dogs: 16 cases (1990-2003)

AIMS: To examine the clinical signs, laboratory and radiographic findings, surgical technique, ureterolith composition, and post-operative outcomes in dogs managed surgically for ureterolithiasis to determine whether surgical removal of ureteroliths in dogs resulted in a positive clinical outcome. METHODS: The medical record database of a university veterinary hospital in Pennsylvania, USA, was searched for dogs that underwent surgery to remove obstructive ureteral calculi between 1990 and 2003. Records were reviewed for signalment, clinical history and examination findings, radiographic and laboratory test results, surgical technique, and ureterolith analysis. Follow-up information was obtained from telephone interviews with owners or referring veterinarians, or by reviewing the medical record of subsequent hospital visits. RESULTS: Sixteen dogs were included in this study; ten were neutered females, two intact females and four castrated males. Abdominal radiography revealed ureteral calculi in 14/16 dogs, renal calculi in 8/16, cystic calculi in 8/16, urethral calculi in 1/16, renomegaly in 6/16 and renal mineralisation in 5/16. Ureterolith type included struvite in six dogs, calcium oxalate in five, calcium phosphate in one, and a mix of struvite, calcium phosphate and calcium oxalate in another. Compared to dogs with non-struvite ureteroliths, those with struvite ureteroliths had a higher pre-operative white blood cell (WBC) count (25.6, SD 7 vs 17.6, SD 6 x 103 cells/mul; p=0.046), and were more likely to have a purulent discharge from the ureteral incision noted at the time of surgery (p=0.015). Following discharge, 14/16 dogs were re-evaluated. Median survival time was 904 days (range 2-1,876). Two dogs required additional surgery on the urinary tract. Four dogs died or were euthanised because of azotaemia and clinical signs related to the urinary system or non-specific signs of illness (vomiting, lethargy) at 8, 90, 333 and 904 days post-operatively. CONCLUSIONS: Surgical management of ureteroliths was successful and resulted in good long-term survival in the majority of dogs examined in this small study population. Similar proportions of calcium oxalate and struvite ureteroliths were identified. CLINICAL RELEVANCE: The use of the ureteral surgery may increase as the frequency of diagnosis of ureteroliths in dogs increases.     

Ultrastructure and chemical composition of calcite urinary calculi in Chinese swamp buffalo

Four urinary calculi, derived from Chinese swamp buffalo, were studied by using qualitative chemical analysis, X-ray diffraction, scanning electron microscopy and qualitative energy dispersive (electron probe) microanalysis. Qualitative chemical analysis showed that the predominant ions were calcium and carbonate with small amounts of magnesium and ammonium. X-ray diffraction confirmed that the calculi were primarily composed of calcium carbonate (calcite). On ultrastructural examination, three apparently distinct structural regions were identified in the calculi: outer large laminations; cavities containing variable numbers of small spheres and rods; and large spheres. There did not appear to be material that acted as a nidus and all regions, on qualitative electron probe analysis, contained primarily calcium with trace amounts of magnesium, phosphorus, potassium and chloride. It was concluded that calcite calculi in Chinese swamp buffalo are probably formed through a process of asynchronous layering and that nidus formation may not be necessary. Moreover, the ultrastructure of the calcite calculi is similar to that reported for siliceous calculi in ruminants and this suggests that similar factors may be involved in their formation.     

Study on precipitation of struvite and struvite-K crystal in goats during onset of urolithiasis

To learn more about the biomineralization process of struvite in ruminants, a seldom noticeable crystal, struvite-K, was investigated in six goats in which urolithiasis was induced by feeding a cottonseed meal and rice straw diet supplemented with MgO. The compositions of crystals and calculi were studied by chemical qualitative analysis and X-ray energy dispersive spectrometry (EDS). The activity product (AP) and relative supersaturation (RSS) of magnesium ammonium phosphate (MAP) and potassium magnesium phosphate (MKP) were calculated to compare the difference of crystals formed in this process. The results showed that calculi consisted of MAP with a little MKP. Crystals in the urine consisted of MAP and MKP before stone formation, but crystals in urine after stone formation mainly consisted of MKP. The AP and RSS of MAP and MKP significantly decreased after stone formation. It was concluded that MAP and MKP may coexist in the crystals of urine before struvite calculi formation but MKP did not precipitate to struvite calculi and was separated out as crystal sedimentation of urine. The changes of crystallization of MAP and MKP contributed partially to the supersaturation status of MAP and MKP during struvite stone formation.     

南京地区犬尿石症的调查及尿结石成分的分析

对南京地区5家具有代表性的动物医院中近2年犬尿石症临床病例进行了系统调查,并应用傅立叶红外光谱、扫描电镜结合X-射线能谱对84个自然病例的尿石样品的成分作了分析。结果表明:(1):南京地区犬尿石症的发病率为0.58%~1.31%,其中雄性占54.02%,雌性占45.98%。(2)南京地区犬尿结石有4种类型,即磷酸铵镁(鸟粪石)、草酸钙、尿酸盐和磷酸钙。描述了各种结石的显微结构特征,并讨论了犬尿石症的发病原因。     

Epidemiology of canine urolithiasis in the Czech Republic from 1997 to 2002

OBJECTIVES: To compare data on the epidemiology of canine urolithiasis in the Czech Republic with that from other countries. METHODS: The records from the Centre for Mineralogical Analysis from 1997 to 2002 were reviewed. The data were obtained from mineralogical analysis of 1366 canine uroliths obtained from patients in the Czech Republic. These included 396 females and 629 males. RESULTS: Sixty-eight breeds plus crossbreeds were identified. Eight breeds plus the crossbreeds accounted for 71.3 per cent of all cases. Males were affected more frequently than females (61.4 per cent versus 38.6 per cent). Struvites significantly predominated in females, while in males calcium oxalates, brushites and cystines were the most common stones. Most of the uroliths (48.9 per cent) were 5 mm or less in dimension. By 2001, struvite was the most frequent (38.5 to 44.1 per cent) urolith, followed by calcium oxalate (26.5 to 32.0 per cent). In 2002, calcium oxalate became the most frequent calculus, followed by struvite, mixed calculi and others. CLINICAL SIGNIFICANCE: Comparison of these results with studies by other authors showed that for most of the monitored parameters there was agreement with respect to the proportions of different breeds within the populations of dogs in different geographical areas.     

Medical dissolution of feline struvite urocystoliths

The efficacy of a diet designed to facilitate dissolution of feline magnesium ammonium phosphate (struvite) uroliths was evaluated in 30 cases of urolithiasis, sterile struvite uroliths dissolved in a mean of 36 days after initiation of dietary treatment. In 5 cases of urolithiasis, struvite urocystoliths associated with urease-negative bacterial urinary tract infection dissolved in a mean of 23 days after initiation of dietary and antimicrobial treatment. In 3 cases of urolithiasis, struvite urocystoliths associated with urease-positive staphylococcal urinary tract infection dissolved in a mean of 79 days after initiation of dietary and antimicrobial treatment. Dissolution of uroliths in cats fed the treatment diet was associated with concomitant remission of dysuria, hematuria, and pyuria, and reduction in urine pH and struvite crystalluria. In one case, a urocystolith composed of 100% ammonium urate, and in another case, a urolith composed of 60% calcium phosphate, 20% calcium oxalate, and 20% magnesium ammonium phosphate did not dissolve.     

Comparison of effect of high intake of magnesium with high intake of phosphorus and potassium on urolithiasis in goats fed with cottonseed meal diet

The effect of high intake of Mg on urolithiasis was compared with high intake of P and K in goats being fed with a cottonseed meal and rice straw diet. Eighteen wether goats were randomly allocated into group A, B and C evenly and fed with cottonseed meal and rice straw diet for three months. From day 60 onwards, KH₂PO₄ and K₂HPO₄ were provided via drinking water to goats in group B to increase the intake of P, K, and MgO to goats in group C to increase the intake of Mg. Blood and urine samples were collected to analyze the concentration of P, K, Mg and Ca, and the activity product (AP) of potassium magnesium phosphate (MKP) in urine was also calculated. The composition of calculi and urinary sedimentary crystals were examined by chemical qualitative analysis, X-ray diffraction, X-ray energy dispersive spectrometry and Fourier transform infrared spectroscopy. The results showed that the incidence of urolithiasis in group C (6/6) was higher than that in group A (1/6) and B (1/6) (P < 0.05). The calculi were mainly composed of magnesium ammonium phosphate (MAP) and partly composed of MKP. MKP presented in crystals of different phases in this experiment. The high intake of Mg contributed to a significant increase of plasma Mg, but additional P, K did not cause a further increase of plasma P, K. Urine P, K, Mg and Ca and AP of MKP in group C decreased significantly after the onset of urolithiasis. In conclusion, high intake of Mg was more important in inducing struvite calculi compared with high intake of K and P in goats under these feeding conditions. Cottonseed meal and rice straw with additional Mg is a good dietary model for inducing struvite calculi in castrated goats.     

Epizootiologic evaluation and quantitative analysis of urinary calculi from 150 cats

One hundred fifty specimens of urinary calculi from 150 cats were analyzed by at least 1 of 4 quantitative methods. Struvite (magnesium ammonium phosphate) was the predominant mineral substance encountered, with 104 (69%) of the calculi being composed entirely of struvite and 23 (15%) being composed partially of struvite. Most (93%) of the calculi were located in the urinary bladder. Growth of bacteria was observed in samples from calculi or urine from 30 (41%) of 74 cats. Coagulase-positive staphylococci were isolated from the urine or calculi from 17 cats (45% of bacteria isolated). Ten other bacterial species were isolated. Median and mean ages of the cats were 5.0 and 5.1 years, respectively. Domestic short-hair and domestic longhair breeds predominated. Fifty-seven percent of the calculi came from females, 43% from males. The distribution by gender did not differ significantly (P greater than 0.2) among the 3 groups (domestic shorthair, domestic longhair, and other). However, the distribution of struvite calculi differed significantly (chi 2 = 15.5, P less than 0.001) by age and gender; among cats less than or equal to 2 years of age, males predominated 2:1 over females, and among cats greater than 2 years of age, females predominated by nearly 3:1 over males. When compared with the general population, females greater than 2 years old were significantly (chi 2 = 15.4, P less than 0.001) overrepresented.     

Cystine calculi I in the dog: an epidemiological retrospective study

During 1970 to 1990, 134 cases of obstructive cystine calculi were diagnosed in Sweden; it was estimated that at least two out of 10,000 male dogs in Sweden had this condition. The disease was found especially in the dachshund, basset hound and Welsh corgi (0–2 to 04 per cent). The study showed that obstructive cystine calculi occur in male dogs of all ages, but not in females or pups. Most cases (53 per cent) were detected at the age of three to five years. Recurrence was common (38 per cent), but was rare in older dogs. Eight dogs which originally had cystine calculi suffered recurrent stones consisting of magnesium ammonium phosphate. Surgery was performed in 40 per cent for the first time (n=122) during the first quarter of the year and in 71 per cent during January to July. Since this condition affects only male dogs after sexual maturity, it was assumed that the formation of cystine calculi involved the sex hormone(s).     

Ultrastructure of selected calcium oxalate-containing urinary calculi from dogs

OBJECTIVE: To elucidate the ultrastructural details of calcium oxalate-containing urinary calculi from dogs. Sample Population-38 specimens selected from a collection of 8,297 oxalate-containing urinary calculi from dogs: 22 specimens composed of calcium oxalate (calcium oxalate monohydrate [COM], calcium oxalate dihydrate [COD], or COM and COD) and 16 specimens composed of calcium oxalate with amorphous calcium phosphate. PROCEDURE: Analyses of specimens included use of plain, reflected, and polarized light microscopy, X-ray diffractometry, scanning electron microscopy (SEM) with backscattered electron (BSE) imagery, and electron microprobe analysis. RESULTS: Four texture types were observed in calcium oxalate calculi; 4 texture types of calcium oxalate-calcium phosphate-mixed calculi were recognized. Texture types were delineated through differences in calcium oxalate crystal sizes, which were affected by urine supersaturation and abundance of crystal nucleation sites. Segregation of calcium oxalate from calcium phosphate indicated they do not precipitate under the same conditions. Deposition of calcium phosphate between calcium oxalate crystals decreased the volume of pore spaces within calculi. Porosity was observed along boundaries between COM and COD. Minute pores increased the surface area of calculi exposed to urine, and this increase in liquid-solid interface promotes interaction of crystals with the surrounding urine. CONCLUSIONS AND CLINICAL RELEVANCE: Calcium oxalate urolithiasis is of major concern, because it is often a recurrent disease among dogs, principally treated by surgical removal of calculi, with few effective dissolution strategies. Understanding the ultrastructure and mineralogic content of calcium oxalate and its association with amorphous calcium phosphate is a step toward the solution of this increasingly important medical problem.     

Instrumental neutron-activation analysis of canine urinary calculi for some selected elements

Thirty canine urinary calculi, most of which had been qualitatively classified as struvite calculi, were analyzed by instrumental neutron activation analysis at the University of Missouri Research Reactor. Measurements of sodium, magnesium, aluminum, silicon, phosphorus, chloride, potassium, and calcium were possible, using a dual irradiation procedure. Magnesium was used to calculate the percentage of struvite mineral, Mg(NH4) (PO4) X 6H2O, in the calculi by making use of the stoichiometric relationship of the element magnesium to the mineral. For those calculi containing greater than 80% struvite, the mean elemental concentrations were found to be 0.12% Na, 9.35% Mg, 0.0033% Al, 12.1% P, 0.02% Cl, 0.85% K, and 2.05% Ca. A new method for determination of silicon in urinary calculi also was discussed. Two calculi were found to contain 45.0% and 37.3% silicon, and 1 mixed calculus was composed of 1.4% silicon.     

Feline urethral plugs and bladder uroliths: a review of 5484 submissions 1998-2003

The results of 5484 submissions from cats to the Canadian Veterinary Urolith Centre between February 1998 and February 2003 are presented. Of the submissions, 618 were urethral plugs and 4866 were bladder uroliths. The majority of the urethral plugs were from male domestic shorthair and longhair cats. Approximately 50% of the urolith submissions were oxalate, 44% were struvite. Oxalate uroliths were the most common mineral type in males and in Himalayan, Persian, and Siamese cats. Struvite uroliths were the most common mineral type in domestic shorthair and longhair cats. Females outnumbered males by 1.4:1 in struvite urolith submissions. A review of risk factors for urethral plugs and bladder uroliths is presented.     

Cystic calculi in two horses

The use of real-time ultrasound for examination of the bladder was a useful diagnostic aid in 2 cases of cystic calculi. The ultrasound procedure revealed that a firm mass palpated per rectum in the bladder of one horse was a calculus. In the other horse, ultrasound revealed additional small uroliths. To remove the uroliths in both horses, laparocystidotomy via a ventral paramedian approach was chosen because it provided the best access to the bladder lumen. The calculi were analyzed by qualitative chemical analysis and quantitative crystallography. Results differed between analysis methods. Crystallography revealed that the mineral composition of both calculi was pure calcium carbonate. Chemical analysis erroneously indicated that the calculi contained phosphate, magnesium, and oxalate.     

Evaluation of trends in frequency of urethrostomy for treatment of urethral obstruction in cats

OBJECTIVE: To determine hospital proportional morbidity rates (HPMR) for urethral obstructions, urethral plugs or urethroliths, and urethrostomies in cats in veterinary teaching hospitals (VTH) in Canada and the United States between 1980 and 1999. DESIGN: Epidemiologic study. ANIMALS: 305,672 cats evaluated at VTH. PROCEDURES: Yearly HPMR were determined for cats with urethral obstructions, urethral plugs or urethroliths, or urethrostomies from data compiled by the Purdue Veterinary Medical Database. The test for a linear trend in proportions was used. RESULTS: Urethral obstructions were reported in 4,683 cats. Yearly HPMR for urethral obstructions declined from 19 cases/1,000 feline evaluations in 1980 to 7 cases/1,000 feline evaluations in 1999. Urethral plugs or urethroliths affected 1,460 cats. Yearly HPMR for urethral plugs or urethroliths decreased from 10 cases/1,000 feline evaluations in 1980 to 2 cases/1,000 feline evaluations in 1999. A total of 2,359 urethrostomies were performed. Yearly HPMR for urethrostomies decreased from 13 cases/1,000 feline evaluations in 1980 to 4 cases/1,000 feline evaluations in 1999. CONCLUSIONS AND CLINICAL RELEVANCE: Frequency of feline urethrostomies performed at VTH in Canada and the United States declined during the past 20 years and paralleled a similar decline in frequency of urethral obstructions and urethral plugs or urethroliths. These trends coincide with widespread use of diets to minimize struvite crystalluria in cats, which is important because struvite has consistently been the predominant mineral in feline urethral plugs during this period.