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.     

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.     

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.     

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。     

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.     

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.     

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.     

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.     

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.     

IN VITRO EVALUATION OF CONTRAST MEDIUM CONCENTRATION AND DEPTH EFFECTS ON THE RADIOGRAPHIC APPEARANCE OF SPECIFIC CANINE UROLITH MINERAL TYPES

Nine pure mineral types of canine uroliths (bladder or urethral origin only) identified in a chronologic sample from the Minnesota Urolith Center were compared to sequential dilutions of iodinated radiographic contrast medium in vitro. The uroliths studied were those composed of 100% magnesium ammonium phosphate, calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate appatite, calcium hydrogen phosphate dihydrate (brushite), ammonium acid urate, sodium acid urate, cystine, and silica. The radiopacity of the uroliths was classified as radiolucent, isopaque, or radiopaque, as compared to the radiopacity of the contrast medium solutions in which they were placed, using 2.0 mm and 5.0 mm depths in petri dishes radiographed using a table-top technique. A statistically significant relationship was found between the effective atomic number of the uroliths and the effective atomic number of the contrast medium solutions to which they were compared for the endpoints of isopacity, first luceney (in increasing iodine concentration sequence), and optimal visualization of internal architecture. In general, uroliths isopaque or radiolucent in contrast medium solutions weaker than 23.5 mgI₂/ml are most likely ammonium acid urate or sodium acid urate. Uroliths isopaque or radiolucent in contrast medium solutions between 23.5 mgI₂/ml and 44.4 mgI₂/ml are probably magnesium ammonium phosphate, cystine, or silica. Uroliths that remained radiopaque in solutions stronger than 44.4 mgI₂/ml, and particularly those radiopaque in contrast medium solutions stronger than 80 mgI₂/ml, almost always contained calcium. This relative opacity assessment is proposed for use in double contrast cystography as an aid in differentiating urolith mineral types clinically to facilitate appropriate use of medical protocols to dissolve uroliths or to prevent their growth or recurrence.     

CONTRAST MEDIUM-RELATED ARTIFACTS OBSERVED DURING IN VITRORADIOGRAPHIC 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.     

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).     

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.     

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.     

Dissolution of a struvite nephrolith in a dog.

A large radiodense calculus in the left renal pelvis of a 22-month-old, male Great Dane disappeared one month following surgical removal of two struvite (magnesium ammonium phosphate) calculi from the right renal pelvis. The dog's urine likely became undersaturated with struvite for a sufficient period to permit dissolution of the renal calculus. Several factors may have contributed to the decrease in urine struvite concentration, including eradication of a urease-producing Proteus sp from the urinary tract and induction of polydipsia and compensatory polyuria by oral administration of sodium chloride.     

Renal calculi in wild Eurasian otters (Lutra lutra) in England

Macroscopic renal calculi were seen in 50 of 492 (10.2 per cent) wild Eurasian otters found dead in England from 1988 to 2007. Forty-eight adults and two subadults were affected. Calculi were present in 15.7 per cent (31 of 197) of adult males and 12.7 per cent (17 of 134) of adult females. There was an increase in prevalence in the study population over time; no calculi were found in 73 otters examined between 1988 and 1996, but in most subsequent years they were observed with increased frequency. Calculi occurred in both kidneys but were more common in the right kidney. They varied greatly in shape and size; larger calculi were mostly seen in the calyces while the smallest ones were commonly found in the renal medulla. Calculi from 45 cases were examined by x-ray diffraction analysis; in 43 (96 per cent), they were composed solely of ammonium acid urate. Affected otters had heavier adrenal glands relative to their body size than unaffected otters (P<0.001). There was no significant association between body condition index and the presence of calculi (P>0.05). Many otters had fresh bite wounds consistent with intraspecific aggression. The proportion bitten increased over time and this coincided with the increased prevalence of renal calculi.     

Canine urolithiasis: epidemiology and analysis of urinary calculi

The incidence of canine urolithiasis was found to lie between 0–5 to 1 per cent of the canine population. Epidemiological and analytical data were collected for 1731 urinary stones, and causal relationships investigated. Calculi were found in 72 breeds. While they were relatively common among dachshunds, dalmatians, cocker spaniels, Pekingese, bassets, poodles, schnauzers and small terrier breeds, urinary stones were relatively rare among German shepherd dogs, boxers, collies, chow chows, old English sheepdogs, spitz and rottweiler breeds. Struvite, which was found in 55-6 per cent of all calculi, proved to be the most common constituent, followed by cystine (22-5 per cent) and ammonium urate (6-6 per cent). Xanthine calculi were rare (six cases), while silicium dioxide calculi were present in only one case. The likelihood of calculi in male animals was twice that of bitches, although the latter were found to be more prone to infection of the urinary tract. Adiposity was present in 29 per cent of all dogs with calculi. The average age of the animals was seven years. In 98-7 per cent of all cases the calculi were found in the lower urinary tract, and surgical removal of the stones was required in 87-5 per cent of cases. The main types of calculi appear among specific breeds, which indicates that a careful breeding programme may help to reduce the frequency of urinary calculi.     

Mouse barley awn (Hordeum murinum) migration induced cystolithiasis in 2 male dogs

Two male dogs were presented with cystic uroliths composed of magnesium ammonium phosphate (struvite). Each had an atypical nidus, a mouse barley awn (Hordeum murinum). To our knowledge, this is the first report of grass awns located in the bladder lumen of dogs. The composition of uroliths and the pathophysiology of grass awn migration to the urinary bladder are discussed.     

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.