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.     

Dietary management of cystic calculi in a horse

Principles in the dietary management of urolithiasis which have been successful in small animal cases were implemented in an equine case. This article describes the dietary management of a horse which repeatedly formed calcium carbonate cystic calculi. Treatment management included progressively decreasing the ration calcium content to reduce the intake of calcium. In addition, urinary tract infections were controlled and urinary acidification was used to inhibit calcium carbonate formation. Successful management was achieved by feeding a 0.2% calcium oat hay ration and administering 175 mg ammonium sulfate per kg body weight orally twice daily for 7 months which produced a urine pH of 5.0. There was no evidence of metabolic acid/base imbalances nor skeletal depletion of calcium. The horse has been free of cystic calculi for an additional 30 months while adequately maintained on a nutritionally balanced oat hay ration. Reducing dietary calcium intake and urine pH are possible management procedures in the horse with recurrent cystic calculi.     

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.     

Glucosuria associated with renal calculi in Asian small-clawed otters

Urine from one female and 2 male Asian small-clawed otters (Aonyx cinerea) with bilateral renal calculi, one female with unilateral calculi, and one nonaffected male were evaluated for abnormal urinary crystalloid excretion. One otter with bilateral renal calculi had cystic calculi composed of calcium oxalate monohydrate and dihydrate. The 2 affected males were littermates, as were the 2 affected females, but the 2 litters were from different parents. At the time of the study, the otters did not have clinical signs of disease. Hematologic and serum biochemical, electrolyte, and enzyme values were normal. The urinary excretion of calcium, oxalate, uric acid, phosphate, citrate, and amino acids in otters with renal calculi was similar to that of the nonaffected otter. The 4 otters with renal calculi had glucosuria but the nonaffected otter did not have glucosuria. The glucosuria, in the absence of hyperglycemia, suggested a renal tubular transport defect for glucose. Other renal abnormalities were not found.     

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.     

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.     

The distribution of canine urinary calculi and their recurrence following treatment

The composition of urinary calculi was determined in 110 cases of canine urolithiasis and it was found that phosphate was the main constituent in 44% of cases, oxalate in 32%, cytsine in 22% and urate in 2%. Magnesium ammonium phosphate calculi were frequently found in female dogs while in male animals calculi composed of calcium salts or cystine were common. The mean age of dogs with calculi composed of magnesium ammonium phosphate was 6 years while for calcium calculi the mean age was 8-6 years and for cystine calculi 4–9 years. Recurrence of urolithiasis was studied in sixty dogs and further calculi were found in thirty-two animals when examined radiographically although only nineteen of these showed clinical signs. Recurrent calculi developed in 75% of cases where the calculi were composed of calcium or cystine but in only 30% of cases with magnesium ammonium phosphate. The recurrent stones usually had a similar composition to the initial calculi. Résumé. On a précisé la composition de calculs urinaires dans 110 cas d'urolithiase canine et or trouvé que le phosphate était le principal constituant dans 44% des cas, l'oxalate dans 32%, cystine dans 22% et l'urate dans 2%. On a fréquemment trouvé des calculs de phosphates d'amrr nium magnésium chez les chiens femelles tandis que chez les animaux mâles les calculs composés sel de calcium ou de cystine étaient communs. La moyenne des âges des chiens avec des calculs coi posés de phosphate d'ammonium magnésium était de 6 ans, alors que pour les calculs de calcium moyenne des âges était de 8,6 ans et pour les calculs de cystine de 4,9 ans. On a étudié une recurren d'urolithiase chez soixante chiens et on a trouvé d'autres calculs chez trente-deux chiens quand i les a examinés à la radiographie bien que dix-neuf seulement aient montré des signes cliniqui Des calculs récurrents se sont développés dans 75% des cas oà les calculs se composaient de cystine i de calcium mais dans seulement 30% des cas avec du phosphate d'ammonium magnésium. L pierres recurrentes avaient généralement une composition semblable à celle des calculs initiaux. Zusammenfassung. Die Komposition von Harnsteinen wurde in 110 Fällen von Hunde-Har steinen bestimmt und man fand, dass Phosphat der Hauptbestandteil in 44% aller Fälle war, Oxal in 32%, Cystin in 22% und Urat in 2%. Magnesiumammoniumphosphatsteine wurden häufig weiblichen Hunden gefunden, während in männlichen Tieren Steine die aus Kalziumsalzen od Cystine zusammengesetzt waren, gewöhnlicher waren. Das Durchschnittsalter von Hunden ir Harnsteinen die aus Magnesiumammoniumphosphat bestanden belief sich um 6 Jahre während fi Kalziumharnsteine das Durchschnittsalter 8,6 Jahre war und für Gystinharnsteine 4,9 Jahre. Ma studierte das Wiederauftreten von Harnsteinen in sechzig Hunden und weitere Harnsteine fande sich in zweiunddreissig Tieren, als sie radiographisch untersucht wurden, obwohl nur neunzehn vo diesen klinische Symptôme zeigten. Emeute Harnsteine entwickelten sich in 75% aller Fälle in dene die Harnsteine aus Cystine oder Kalzium zusammengesetzt waren aber in nur 30% von Fällen m Magnesiumammoniumphosphat. Die erneut auftretenden Steine waren gewöhnlich von ähnlichi Komposition wie die anfänglichen Harnsteine.     

Urolithiasis in a wild red deer (Cervus elaphus) population

Renal calculi were found in eight of 325 red deer kidney pairs examined, all eight were females and only one was infected in both kidneys. A further three deer badly infected with urolithiasis were found by chance, two were males. Examples of the calculi found are illustrated to show their range of sizes and shapes. One calculus analysed for chemical composition comprised predominantly calcium carbonate.     

Evaluation of trends in urolith composition in cats: 5,230 cases (1985-2004)

OBJECTIVE: To determine trends in urolith composition in cats. DESIGN: Retrospective case series. SAMPLE POPULATION: 5,230 uroliths. PROCEDURES: The laboratory database for the Gerald V. Ling Urinary Stone Analysis Laboratory was searched for all urolith submissions from cats from 1985 through 2004. Submission forms were reviewed, and each cat's age, sex, breed, and stone location were recorded. RESULTS: Minerals identified included struvite, calcium oxalate, urates, dried solidified blood, apatite, brushite, cystine, silica, potassium magnesium pyrophosphate, xanthine, and newberyite. During the past 20 years, the ratio of calcium oxalate stones to struvite stones increased significantly. When only the last 3 years of the study period were included, the percentage of struvite stones (44%) was higher than the percentage of calcium oxa-late stones (40%). The most common location for both types of uroliths was the bladder. The number of calcium oxalate-containing calculi in the upper portion of the urinary tract increased significantly during the study period. The number of apatite uroliths declined significantly and that of dried solidified blood stones increased significantly, compared with all other stone types. No significant difference in the number of urate stones was detected. CONCLUSIONS AND CLINICAL RELEVANCE: The increasing proportion of calcium oxalate uroliths was in accordance with findings from other studies and could be a result of alterations in cats' diets. However, the decreased percentage of calcium oxalate calculi and increased percentage of struvite calculi observed in the last 3 years may portend a change in the frequency of this type of urolith.     

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.     

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.     

Radiographic features of suspected suture‐associated cystic calculi in dogs

This retrospective case series describes the radiographic features of suspected suture‐associated cystic calculi in six dogs with a history of at least one or multiple prior cystotomies. One of the dogs presented twice. Suspected suture‐associated cystic calculi were multifocal, short, predominantly linear mineral opacities localized in the center of the urinary bladder on abdominal radiographs. One patient (n = 1) presented with multifocal round, pin point, and linear radiopaque calculi. The calculi were all calcium oxalate in composition. On gross examination, the calculi had a hollow center. Six cystotomies used monofilament absorbable suture material (polydioxanone [n = 4] or poliglecaprone 25 [n = 1]) in prior cystotomies. Suture material in two of the cases was unknown. Suspected suture‐associated cystic calculi are a rare occurrence in veterinary medicine but should be considered in dogs that have a history of prior cystotomy, hollow core on gross analysis, and radiographic evidence of mineral opaque, predominantly linear, cystic calculi.     

Analysis of feline urinary calculi and urethral plugs by infrared spectroscopy and scanning electron microscopy

The chemical constituents of 34 feline urinary calculi and five urethral plugs were analysed by infrared spectroscopy. The analysis revealed that 18 (52.9 per cent) of the calculi contained magnesium ammonium phosphate hexahydrate (struvite) as the major component; 10 (29.4 per cent) contained complex ammonium urates (three of them also containing calcium phosphate, mainly on the surface); three were composed of calcium phosphates and three were composed mainly of calcium oxalate mono and dihydrates. The urethral plugs were composed primarily of struvite, but also contained large amounts of organic matter. The examination of 16 selected samples by scanning electron microscopy and electron dispersive x-ray analysis revealed that their crystalline structures were similar to those of canine stones.     

Silicate renal calculi in Kenyan dogs

Renal calculi were detected in 124 (53%) of 241 native Kenyan dogs during a necropsy survey for Spirocerca lupi infection. Affected kidneys were grossly normal but histologically pyelitis was present in 33% of the dogs. Over 50% of the stones were bilateral. Most were small and yellowish, the largest one was 2.5 cm. One native dog had a cystic calculus that obstructed its bladder.
Chemical analysis of the calculi revealed only traces of magnesium and phosphate. Emission spectrum studies identified the calculi as magnesium calcium aluminum silicate.
Decreased water intake or increased insensitive water loss do not seem to be important causative factors. Silica levels in water and maize should be determined.     

Clinical, clinicopathologic, radiographic, and ultrasonographic abnormalities in cats with ureteral calculi: 163 cases (1984-2002)

OBJECTIVE: To determine clinical, clinicopathologic, radiographic, and ultrasonographic abnormalities in cats with ureteral calculi. DESIGN: Retrospective study. ANIMALS: 163 client-owned cats. PROCEDURE: Medical records were reviewed, and information on signalment, history, clinical signs, and results of clinicopathologic testing and diagnostic imaging was obtained. RESULTS: The number of cats in which ureterolithiasis was diagnosed each year increased progressively during the study period. Clinical signs tended to be non-specific and included inappetence, vomiting, lethargy, and weight loss. A combination of survey radiography and abdominal ultrasonography revealed ureteral calculi in 66 of 73 (90%) cats in which the diagnosis was confirmed at surgery or necropsy. Ultrasonography revealed that ureteral calculi were causing ureteral obstruction in 143 of 155 (92%) cats. One hundred thirty-four of 162 (83%) cats had azotemia, 84 of 156 (54%) had hyperphosphatemia, and 22 of 152 (14%) had hypercalcemia. Urinary tract infection was documented in 10 of 119 (8%). Fifty-eight of 76 (76%) cats with unilateral ureterolithiasis had azotemia and 33 (43%) had hyperphosphatemia, indicating impairment of renal function in the contralateral kidney or prerenal azotemia. Ultrasonographic imaging of the contralateral kidney in cats with unilateral ureteral calculi suggested that preexisting renal parenchymal disease was common in cats with ureterolithiasis. Ninety-one of 93 (98%) ureteral calculi contained calcium oxalate. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that abdominal imaging should be performed in all cats with chronic nonspecific signs or with acute or chronic renal failure to rule out ureterolithiasis. Preexisting renal disease may be common in cats with ureteral calculi.     

CALCIUM OXALATE URETEROLITH IN A CAT

A 4-year-old cat was presented for polyuria and polydipsia. Unilateral hydronephorosis and hydroureter was diagnosed on ultrasound examination of the abdomen, and right ureteral calculi were seen in survey abdominal radiographs. Intravenous urography confirmed hydronephrosis and indicated poor renal funttion in the right kidney. Surgical removal of the ureteral calculus improved right renal function. Analysis of the calculus indicated composition of calcium oxalate, an uncommon calculus in cats.     

Pathological findings in the bulbourethral glands of bulls

The bulbourethral glands of 323 Bos indicus or B. indicus crossbred bulls more than 1 1/2 years old were examined in an abattoir study. Bulbourethral adenitis was diagnosed grossly and confirmed by histological examination in 4 (1.2%). Unilateral chronic interstitial inflammation was seen in 2 cases; one of these was associated with a degenerative-type seminal vesiculitis. In the others adenitis was bilateral; in one case it was associated with a concretion and foreign (plant) material in the principal duct of the left bulbourethral gland; in the other bilateral case, numerous calculi were present and microscopically, a chronic active and diffuse inflammation was observed. Chemical analysis of the calculi showed calcium oxalate and tricalcium phosphate to be the most important components. Corynebacterium spp was isolated from the lesion with multiple calculi but attempts to isolate Chlamydia spp, Mycoplasma spp and Brucella abortus from the 4 adenitis cases were unsuccessful. Congenital abnormalities such as glandular fusion (2.2%) or unilateral aplasia (0.6%) were also observed. Cysts were the most common finding (19.2%), and duct dilation was frequent (7.1%). The significance of these findings in relation to fertility is considered.     

Changes in proportion of canine urinary calculi composed of calcium oxalate or struvite in specimens analyzed from 1981 through 2001

The objective of this report was to characterize 20-year changes in proportion of calcium oxalate (CaOx) calculi and struvite calculi in dogs, and associations with breed, age, and sex. In this retrospective study, results of analysis of urinary calculi from dogs were reviewed for specimens received between July 1, 1981, and December 31, 2001. Breed, sex, age, year of submission of the specimen, and mineral type(s) were analyzed statistically. CaOx or Struvite or both were contained in 18,966 of 20,884 (91%) specimens. For both sexes, a 20-year statistically significant increase was observed in the proportion of calculus specimens that contained CaOx. The increase in this proportion was greater in females (1% to 31%) than in males (18% to 82%). From 1998 to 2001, when proportions may have plateaued, the odds of specimens containing CaOx were markedly higher in 18 breeds, markedly lower in 5 breeds, and not significantly different in 13 breeds compared with crossbreds. For both sexes, a 20-year statistically significant decrease was observed in the proportion of calculus specimens that contained struvite. This decrease in proportion was greater for males (79-16%) than for females (97-68%). From 1998 to 2001, when proportions plateaued, the odds of calculi containing struvite were markedly lower in 20 breeds, markedly higher in 1 breed, and not significantly different in 15 breeds when compared with crossbreds. Breed, age, and sex were associated statistically with CaOx or struvite urolithiasis. In conclusion, there appears to have been a long-term increase in the proportion of specimens of canine urinary calculi that contain CaOx as well as a long-term decrease in the proportion of specimens of calculi that contain struvite for both male and female dogs. The rate of change appeared to begin leveling off in the period 1998 to 2001. The recent proportion of dogs with either CaOx- or struvite-associated urolithiasis may depend on breed, age, and sex, and on interactions among these 3 factors.     

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。