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.     

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.     

Inheritance of urinary calculi in the Dalmatian

Dalmatians are unique among dogs in that they excrete uric acid in their urine as the end product of purine metabolism rather than allantoin as do other breeds of dogs. Urinary calculi form from urate (salts of uric acid) and can cause urethral obstruction in male Dalmatians. Although all Dalmatians have the primary defect, only a subset develops clinical disease. We postulated that calculi formation might have a genetic component that segregates within the breed, causing some animals to form calculi and others to never form calculi despite excreting uric acid in their urine. We used a survey to ascertain the urinary calculi status based on clinical signs of adult Dalmatians aged 6 years or older, and we used pedigrees from these same animals to estimate the heritability of the clinical manifestation of urate calculi within the breed to be .87 (.75-.96). The prevalence of the disease was 34% (24.99-43.70%) among male Dalmatians in our survey. The high heritability of the disease makes it possible for breeders to effectively select against the disease.     

Crystalline composition of equine urinary calculi

X-ray diffraction crystallography was used to determine the crystalline composition of 18 equine urinary calculi, including stones originating in the kidney, bladder and urethra. Calcium carbonate in the form of calcite was found to be the major component in all calculi examined. Other components commonly found included weddellite and substituted vaterite. Urine deposits from a number of normal horses were also examined. The significance of these findings, as well as those from a number of previous reports, are discussed in relation to the possible aetiology of urolithiasis in the horse.     

The structure of canine urinary calculi

Thin sections of canine calculi were examined using microradiographic techniques and although nuclei were detected in a few stones, their presence did not appear to be necessary for the formation of canine calculi. Concentrically arranged laminar bands were seen in the majority of magnesium ammonium phosphate calculi, but radial striation was seen only in one stone which was composed of ammonium urate. Fissures were observed in the centres of several calculi composed of magnesium ammonium phosphate.     

Xanthine-containing urinary calculi in dogs given allopurinol

Clinical features and laboratory findings were evaluated in 10 dogs that formed xanthine-containing urinary calculi during the period that they were given allopurinol (9 to 38 mg/kg of body weight/d). Duration of allopurinol treatment was 5 weeks to 6 years. Of the 10 dogs, 9 (all Dalmatians) had formed uric acid-containing calculi at least once before allopurinol treatment was initiated. It was not possible to recognize xanthine as a crystalline component of the calculi by use of a chemical colorimetric method or by polarized light microscopy. We concluded that the best diagnostic method for recognition of xanthine-containing calculi was high-pressure liquid chromatography because it is quantitative, sensitive, and accurate, and can be conducted on a small amount (1 to 2 mg) of crystalline material.     

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.     

Dried solidified blood calculi in the urinary tract of cats

We have noted an increased number of calculi submitted to the Gerald V. Ling Urinary Stone Analysis Laboratory, University of California, Davis, that do not contain crystalline material but appear to be composed of dried solidified blood (DSB). Canine and feline laboratory records from 1986-2003 were reviewed for samples composed of >99% DSB. No calculi from dogs were found, but specimens from 49 cats were composed of >99% DSB, of which almost half (n = 22) had been submitted after 2001. The DSB calculi had been removed surgically or by postmortem examination from all areas of the upper and lower urinary tract. All samples were well formed and could be divided in half with Rongeur forceps. Detailed case information was available for 12 cats. Urinalyses were available for 9 of the 12 cats, and the mean specific gravity was 1.017 (range, 1.009-1.032). Red blood cells were reported in the sediment of all cats, with most containing >100 RBC/hpf. Ureteral obstructions but no radio-opaque calculi were visible by radiography, including radiographic contrast studies. Reports of ultrasound examinations were available for 10 cats, and discrete calculi were not recorded. In addition to polarized light microscopy, infrared spectroscopy and electron probe microanalysis were performed on a subset (n = 6, DSB calculi; n = 3, control calculi) of samples. Significantly more carbon, nitrogen, and sulfur (P = .012, P = .02, and P = .012, respectively) were present in the elemental analysis of the DSB calculi than in the control calculi, suggesting that the DSB calculi are primarily formed from organic material. At this time, we are uncertain why these DSB calculi become solidified, and we recommend that samples be submitted both in formalin and preservative free to further investigate their etiology.     

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.