Update: Management of calcium oxalate uroliths in dogs and cats.

Calcium oxalate has become the most common mineral occurring in canine and feline uroliths. Although calcium oxalate urolith formation may be a consequence of metabolic disease, the underlying cause is not identified in many dogs and cats. Currently, there is no successful medical dissolution protocol, and calcium oxalate uroliths must be removed physically if causing problems. Effective preventative protocols are available for dogs and cats, although they are not uniformly successful.     

In vitro evaluation of canine and feline calcium oxalate urolith fragility via shock wave lithotripsy

OBJECTIVE: To test the hypothesis that feline calcium oxalate uroliths are intrinsically more resistant to comminution via shock wave lithotripsy (SWL) than canine calcium oxalate uroliths through comparison of the fragility of canine and feline uroliths in a quantitative in vitro test system. SAMPLE POPULATION: Calcium oxalate uroliths (previously obtained from dogs and cats) were matched by size and mineral composition to create 7 pairs of uroliths (1 canine and 1 feline urolith/pair). PROCEDURE: Uroliths were treated in vitro with 100 shock waves (20 kV; 1 Hz) by use of an electrohydraulic lithotripter. Urolith fragmentation was quantitatively assessed via determination of the percentage increase in projected area (calculated from the digital image area of each urolith before and after SWL). RESULTS: After SWL, canine uroliths (n = 7) fragmented to produce a mean +/- SD increase in image area of 238 +/- 104%, whereas feline uroliths (7) underwent significantly less fragmentation (mean image area increase of 78 +/- 97%). The post-SWL increase in fragment image area in 4 of 7 feline uroliths was < 50%, whereas it was > 150% in 6 of 7 canine uroliths. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that feline calcium oxalate uroliths are less susceptible to fragmentation via SWL than canine calcium oxalate uroliths. In some cats, SWL may not be efficacious for fragmentation of calcium oxalate nephroliths or ureteroliths because the high numbers of shock waves required to adequately fragment the uroliths may cause renal injury.     

Canine and feline urolithiasis: Examination of over 50 000 urolith submissions to the Canadian Veterinary Urolith Centre from 1998 to 2008

This study reports on trends in canine and feline urolithiasis in Canada during the past 10 years. Age, sex, breed of animals and mineral composition from 40 637 canine and 11 353 feline bladder uroliths submitted to the Canadian Veterinary Urolith Centre between 1998 and 2008 were recorded. Struvite and calcium oxalate uroliths comprised > 85% of all uroliths submitted. In dogs, the number of struvite submissions has declined and the number of calcium oxalate submissions has increased. Struvite uroliths were most common in female dogs and calcium oxalate uroliths in male dogs. The shih tzu, miniature schnauzer, bichon frisé, lhasa apso, and Yorkshire terrier were the breeds most commonly affected for both struvite and calcium oxalate uroliths. Urate uroliths were most common in male dalmatians. In cats, struvite submissions declined and calcium oxalate submissions remained constant. Struvite and calcium oxalate uroliths were common in domestic, Himalayan, Persian, and Siamese cats. Urate uroliths were over-represented in Egyptian maus.     

Analysis of 4495 canine and feline uroliths in the Benelux. A retrospective study: 1994-2004

From 1994 to 2004, Hill's Pet Nutrition received 4495 canine (65%) and feline (35%) uroliths from Benelux veterinary practitioners. They were sent to the Minnesota Urolith Center, USA for analysis. In 1994, 110 uroliths were analysed - 85% from dogs - and in 2003, 1067 uroliths were analysed - 59% from dogs. During this period, substantial changes were observed in composition. In 1994, 77% of the cats had uroliths composed of struvite, and 12% had uroliths composed of calcium oxalate. In 2003, feline uroliths were composed of 32% struvite, and 61% calcium oxalate. The same evolution was observed in the dogs. In 1994, 51% of canine uroliths were composed of struvite, and 33% of calcium oxalate. In 2003, 40% had struvite uroliths, and 46% had calcium oxalate uroliths. A significant effect of the size, the breed, and the gender were noticed in the dogs. The mean age of uroliths appearance was 7.3 years in the dogs and 7.2 years in the cats. The findings are similar to those previously published in the USA.     

Relationship of nutritional factors to the cause, dissolution, and prevention of canine uroliths

Nutritional factors play a variable role in the etiopathogenesis of canine struvite, ammonium urate, cysteine, calcium oxalate, and silica uroliths. Knowledge of these factors allows modification of diets to promote dissolution of selected minerals within uroliths.     

Qualitative and quantitative analysis of uroliths in dogs: definitive determination of chemical type

Effective treatment and prevention of urolithiasis depends on accurate determination of the chemical nature of the uroliths. A widely used qualitative chemical procedure was compared with quantitative crystallographic analysis of 272 canine uroliths. Agreement between the 2 methods was 78%. Qualitative analysis failed to detect 62% of calcium-containing uroliths and 83% of carbonate apatite uroliths. Qualitative analysis gave false-positive results for urates in 55% of cystine uroliths. Mixed uroliths comprising 6% of the total could not be classified without quantitative analysis. Silicate, cystine, and urate uroliths generally were of pure composition. Crystallographic analysis indicated the following distribution of major types: struvite, 69%; calcium oxalate, 10%; urate, 7%; silicate, 3.5%; cystine, 3.2%; calcium phosphate, 1%; and mixed, 6%. Among dogs with struvite uroliths, 66% had positive results of bacterial culturing from the urinary bladder. Six breeds (Miniature Schnauzer, Welsh Corgi, Lhasa Apso, Yorkshire Terrier, Pekingese, and Pug) had a significantly higher risk for urolithiasis, compared with other breeds. The German Shepherd Dog had a significantly lowered risk, compared with other breeds. Two breeds had significant relationship to a specific type of urolith: Miniature Schnauzer for oxalate, and Dalmatian for urate (P less than 0.001). It was concluded that quantitative analysis, using crystallography, was superior for the detection of calcium oxalate, carbonate apatite, cystine, urate, and mixed uroliths.     

Analysis of uroliths from cats and dogs in New Zealand, 1993-96

AIMS: Canine and feline uroliths were analysed to determine the prevalence of particular types of urolith and the dog breeds at risk. METHODS: Three hundred and sixty-nine uroliths recovered from 316 dogs and 53 cats between November 1993 and December 1996 were analysed by X-ray diffraction, and by infrared spectrometry where X-ray diffraction alone was non-diagnostic. RESULTS: Bitches of small breeds especially Welsh corgi and Bichon frise, were most frequently affected. Struvite was the most common urolith (204 dogs). Oxalate (60 dogs) was the second most prevalent urolith identified, followed by cystine (24 dogs). The breeds producing cystine calculi were: Dalmatian, Bassett hound, Borzoi, Newfoundland, Shetland sheepdog, Labrador, Chihuahua, Fox terrier, English bulldog, Bichon frise, Doberman pinscher, Border collie. Silica uroliths were identified for the first time in New Zealand. All feline uroliths were struvite. CONCLUSION: The results are useful in determining the prevalence of specific types of urolith in New Zealand and the breeds at risk of forming them.     

TWINKLING ARTIFACT IN SMALL ANIMAL COLOR-DOPPLER SONOGRAPHY

Twinkling artifact is a recently described color-Doppler phenomenon that has not been studied in the veterinary field. Our purpose was to assess the grade of the artifact in vitro with varying urolith compositions, and to evaluate its potential role in clinical practice. Five canine and feline uroliths types of 100% mineral composition were studied in vitro with color-Doppler sonography, and a prospective study was performed in 41 patients with renal, bladder, gallbladder, or digestive focal hyperechogenicities. The images were analyzed for the presence and the grade of the artifact. Phantom study demonstrated the constant occurrence of the artifact regardless of the mineral composition of uroliths. Mottled and rough surfaced stones produced higher grades of twinkling artifact. High-grade, color-twinkling artifact generated by stones occured frequently in vivo. Bladder crystalluria was more frequently detected by artifact visualization than sample urinalysis performed by cystocentesis. In veterinary medicine, twinkling artifact may thus be considered an additional sonographic feature of urinary stones, and can lead to a more appropriate management of patients presenting gray-scale sonographic focal hyperechogenicities.     

Canine urolithiasis: a look at over 16 000 urolith submissions to the Canadian Veterinary Urolith Centre from February 1998 to April 2003

The purpose of this study was to report on the age, sex, breed, and mineral composition of 16 647 canine bladder uroliths submitted to the Canadian Veterinary Urolith Centre between February 1998 and April 2003. Each urolith submission was accompanied by a questionnaire. Of the submissions, approximately 43.8% were struvite and 41.5% oxalate. Struvite uroliths were most common in female dogs. Mixed breed dogs predominated, followed by the shih tzu, bichon frise, miniature schnauzer, Lhasa apso, and Yorkshire terrier. Oxalate uroliths were most common in males and in the miniature schnauzer, bichon frise, Lhasa apso, shih tzu, and Yorkshire terrier. Urate uroliths were most common in male Dalmations. Other urolith types, including cystine, xanthine, silica, and calcium phosphate, were less commonly reported. A review of risk factors for the various uroliths is presented, along with some recommendations for treatment and prevention.     

Dissolution of canine ammonium urate uroliths

Medical therapy that may be effective in promoting dissolution of canine ammonium urate uroliths includes the following: reduction of dietary purines, reduction in in vivo production of uric acid, and alkalinization of urine.     

Nutrition and aspects of feline lower urinary tract disease

Important causes of feline lower urinary tract disease (LUTD) that have been identified include urolithiasis and the formation of urethral plugs. In many cases, however, no specific cause of disease may be evident. Clinical studies in cats with apparently ‘idiopathic’ feline LUTD have suggested that some cases may respond to dietary modification, with diets designed to acidify urine, provide a good urine volume and relatively restricted magnesium intake. Nutritional research has predominantly focused on factors that may contribute to the formation of struvite uroliths, and has resulted in the development of specific recommendations for the management and subsequent prevention of recurrence of this condition. Urethral plugs have been less well studied, although recent clinical observations provide evidence that dietary modification may be of value in preventing their recurrence.     

Evaluation of 21 426 feline bladder urolith submissions to the Canadian Veterinary Urolith Centre (1998–2014)

This study reports emerging trends in feline urolithiasis in Canada during the past 16.8 y, evaluates associations of breed and gender with urolith types, and reports on feline submissions from outside of Canada. Struvite and calcium oxalate uroliths comprised > 90% of all uroliths submitted. In cats, oxalate submissions outnumbered struvite submissions from Canada, Hong Kong, Denmark, and the United Arab Emirates, while Australian struvite submissions outnumbered calcium oxalate submissions. In Canada, the majority of urolith submissions were from domestic cats followed by Himalayan, Persian, and Siamese cats. Males were more likely to form calcium oxalate uroliths and females were more likely to develop struvite uroliths. Compared to domestic short-haired cats, Tonkinese, Burmese, Devon rex, Himalayan, Persian, and Siamese cats were significantly associated with calcium oxalate urolith submission. Egyptian mau, Birman, ocicat, and Siamese breeds were over-represented amongst urate submissions.     

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.     

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.     

Duration of immunity for canine and feline vaccines: a review

In our studies aimed at assessing the minimum duration of vaccinal immunity (DOI), approximately 1000 dogs have been vaccinated with products from all the major US veterinary biological companies. The DOI for the various products is determined by antibody titers for all dogs and, by challenge studies in selected groups of dogs. Recently, all major companies that make canine vaccines for the U.S. market have completed their own studies; published data show a 3 years or longer minimum DOI for the canine core products, canine distemper virus (CDV), canine parvovirus type 2 (CPV-2), and canine adenovirus-2 (CAV-2). Studies with feline core vaccines - feline parvovirus (FPV), calicivirus (FCV) and herpes virus type I (FHV-1) have shown a minimum DOI of greater than 3 years. Based on these results, the current canine and feline guidelines (which recommend that the last dose of core vaccines be given to puppies and kittens > or =12 weeks of age or older, then revaccination again at 1 year, then not more often than every 3 years) should provide a level of protection equal to that achieved by annual revaccination. In contrast, the non-core canine and feline vaccines, perhaps with the exception of feline leukaemia vaccines, provide immunity for < or =1 year. In general the effectiveness of the non-core products is less than the core products. Thus, when required, non-core vaccines should be administered yearly, or even more frequently.     

Prevalence of calcium oxalate uroliths in miniature schnauzers.

Epidemiologic data were evaluated from all dogs admitted to the University of Minnesota, Veterinary Teaching Hospital (UMVTH) between June 1981 and November 1989. Of 69,890 admissions, 2,077 were Miniature Schnauzers. Uroliths were retrieved from 63 of the 2,077 Miniature Schnauzers admitted. In 20 of the 63 urolith episodes, calcium oxalate was the predominant mineral identified. By comparison, calcium oxalate uroliths were identified in only 56 of the remaining 67,813 non-Miniature Schnauzer canine admissions. The odds that uroliths from Miniature Schnauzers were composed of calcium oxalate was 11.8 times greater than for other canine breeds evaluated at the UMVTH (95% confidence interval = 6.8 to 20.1). Data also were evaluated from files of uroliths retrieved from dogs and submitted to the Minnesota Urolith Center for quantitative mineral analysis, between June 1981 and November 1989. Of 3,930 uroliths analyzed, 615 (15.6%) uroliths were obtained from Miniature Schnauzers. of the 615 uroliths, 175 (28.4%) were calcium oxalate. By comparison, only 550 (16.6%) of the remaining 3,315 from dogs of breeds other than Miniature Schnauzers were calcium oxalate. The odds that uroliths submitted for analysis were composed of calcium oxalate was 2 times greater for Miniature Schnauzers than for dogs of other breeds (95% confidence interval = 1.6 to 2.4). Calcium oxalate uroliths were retrieved more frequently in males than females. The risk for males developing calcium oxalate uroliths was greater than 3 times the risk for females in both groups of data evaluated. The mean age of all Miniature Schnauzers admitted to the UMVTH with calcium oxalate uroliths was 9 years. Calcium oxalate uroliths were not detected in Miniature Schnauzers younger than 1.7 years.     

Medical management of male and female cats with nonobstructive lower urinary tract disease

This case is typical of recurrent urolithiasis managed by repeated surgery. Retrospective assessment of the disorder indicates the need for quantitative analyses of uroliths removed by cystotomy. Compliance of the owners with recommendations to minimize recurrent urolithiasis might have been beneficial. Results of medical therapy designed to induce dissolution of uroliths in this case are representative of preliminary findings of medical dissolution of naturally occurring struvite uroliths in ten other cats. It is of interest that the uroliths dissolved even though no effort was made to induce diuresis. The underlying cause of UTI in this patient may have been damage to the lower urinary tract induced by previous diagnostic and therapeutic procedures and/or sterile struvite uroliths that compromised local host defense mechanisms. Lack of urease production by the uropathogens suggests that they did not play a causative role in formation of uroliths. The need for preventative therapy of recurrent formation of uroliths after their medical dissolution is worthy of further comment. In this patient, specific measures to prevent urolith recurrence were not initiated because it is a part of a prospective clinical study. In the event uroliths recur, medical therapy designed to induce dissolution of uroliths would be repeated. Need for long-term preventative therapy would be dependent on the time interval between recurrent episodes (weeks, months, or years), and the effectiveness of medical therapy for urolith dissolution. Long-term prophylactic therapy would include urine acidifiers and diets low in magnesium.     

An update on aspects of viral gastrointestinal diseases of dogs and cats

Viruses commonly cause gastrointestinal illnesses in dogs and cats that range in severity from mild diarrhoea to malignant neoplasia. Perpetual evolution of viruses is reflected in changing disease patterns, so that familiar viruses are sometimes discovered to cause new or unexpected diseases. For example, canine parvovirus (CPV) has regained the ability to infect felids and cause a panleucopenia-like illness. Feline panleucopenia virus (FPV) has been shown to cause fading in young kittens and has recently been implicated as a possible cause of feline idiopathic cardiomyopathy. Molecular scrutiny of viral diseases sometimes permits deeper understanding of pathogenesis and epizootiology. Feline gastrointestinal lymphomas have not, in the past, been strongly associated with retroviral infections, yet some of these tumours harbour retroviral proviruses. Feline leukaemia virus (FeLV) may play a role in lymphomagenesis, even in cats diagnosed as uninfected using conventional criteria. There is strong evidence that feline immunodeficiency virus (FIV) can also be oncogenic. The variant feline coronaviruses that cause invariably-fatal feline infectious peritonitis (FIP) arise by sporadic mutation of an ubiquitous and only mildly pathogenic feline enteric coronavirus (FECV); a finding that has substantial management implications for cat breeders and veterinarians. Conversely, canine enteric coronavirus (CECV) shows considerable genetic and antigenic diversity but causes only mild, self-limiting diarrhoea in puppies. Routine vaccination against this virus is not recommended. Although parvoviruses, coronaviruses and retroviruses are the most important known viral causes of canine and feline gastrointestinal disease, other viruses play a role. Feline and canine rotaviruses have combined with human rotaviruses to produce new, reassortant, zoonotic viruses. Some companion animal rotaviruses can infect humans directly. Undoubtedly, further viral causes of canine and feline gastrointestinal disease await discovery.