Urolithiasis in the maned wolf ( Chrysocyon brachyurus ...

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Braz. J. vet. Res. anim. Sci., São Paulo, v. 44, n. 5, p. 352-357, 2007

Urolithiasis in the maned wolf (Chrysocyonbrachyurus): Assessment of four clinical cases in

captivity

1 - CBMM Environmental Development Center - Companhia Brasileira de Metalurgiae Mineração, Araxá - MG2 - CBMM Research Center - Companhia Brasileira de Metalurgia e Mineração,Araxá - MG

Laura Teodoro de OliveiraFERNANDES1

Maria das Graças MendesMARCOLINO2

Correspondende to:Caixa Postal 08, CEP 38183-970 –Araxá – MG Tel: (55) 34-3669-3511 /Fax: (55) 34-3669-3500email – [email protected]

Recebido para publicação: 20/01/2006Aprovado para publicação: 23/08/2007

Abstract

Four cases of urolithiasis in captive maned wolves (Chrysocyonbrachyurus) were studied. All four animals were adult males. The clinicalcases occurred in the period 1989-2004. The disease was manifestedafter 2 months to 10 years of captivity. The main clinical symptomsfound were abdominal distension, recurrent urinary tract infections,pain upon abdominal palpation, difficulty urinating, polacyuria,hematuria, anorexia, dehydration, and urinary tenesmus evolving toanuria due to obstruction of the urethra by calculi. Radiologicalexamination detected bladder distension and the presence of manyradio-opaque uroliths in the bladder lumen. Diffraction analysis ofuroliths showed they were made up of calcium acid pyrophosphateand basic hydrous manganese phosphate (n=1) and hydrousmagnesium ammonium phosphate with traces of PotassiumCalcium Phosphate (n=1). Electron microscopy showed that urolithsconsisted of crystals with mineral phosphorus, potassium andmagnesium (n=2) predominating in their composition. This is thefirst time any scientific research has demonstrated the occurrence ofurolithiasis associated with uroliths of mineral composition basedon phosphate, potassium and magnesium in captive maned wolves.The only cases of urolithiasis in maned wolves documented hithertowere cystine-related. Therapeutic measures for urolithiasis involveappropriate nutritional management, use of medication and, in somecases, specific surgical procedures. Diagnosis and treatment of thediseases to which wild animals are subject when in captivity are extremelyimportant for maintenance and reproduction of these species with aview to their conservation in the environment.

Key words:Maned wolf.Urolithiasis.Mineral compositionof uroliths.Clinical symptoms ofurolithiasis.

Introduction

The maned wolf, Chrysocyon brachyurus(Illiger 1811), is a carnivorous mammalianof the Canidae family which inhabits areasfrom the Northeast of Brazil to northernArgentina, Paraguay, eastern Bolivia andwestern Peru.1 In Brazil it is officially classifiedas an endangered species under Ministry ofthe Environment Normative Instruction 03/2003. It is a solitary animal with crepuscularto nocturnal activity patterns. In the wild itfeeds mostly on small vertebrates, fruits and

berries.2 Urolithiasis is not a specific diseasebut secondary to underlying disorders. It ischaracterized by the formation of stones orcalculi (uroliths) in the kidneys, ureters and/or bladder. Uroliths are formed when thereis an increase in the conditions that favorstheir development, such as urinary tractinfections, unbalanced diet and geneticpredisposition.3 The purpose of this studywas to assess the clinical, radiological andhistopathological profiles of urolithiasis inmaned wolves kept in captivity; to analyzeurolith composition qualitatively and

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quantitatively; and to propose strategies forearly diagnosis of the disease as well assuitable treatment for affected animals.

Material and Method

Four cases of urolithiasis in manedwolves were studied. All four cases occurredin the period 1989-2004 at the CaptiveBreeding Compound, a unit of CompanhiaBrasileira de Metalurgia Mineração -CBMM’s Environmental DevelopmentCenter near Araxá, Minas Gerais, Brazil. Datawere analyzed and compiled from clinicalrecords and autopsy reports on diseasedanimals. Uroliths found during clinical orpostmortem examination were analyzed atCBMM’s Research Center, by X-raydiffraction (XRD), using a Rigaku Geigerflex,and scanning electron microscopy (SEM),using a Cambridge Instruments S200 withEDS. For XRD, each urolith sample wascarefully ground into a powder and loadedinto a sample port. For the SEM analysis,uroliths were first dried at 60ºC and thenmetallized with carbon.

Results

The analyses showed that clinical casesoccurred in four adult males, with threeresulting in death. Half the animals originatedfrom the wild (n=2) and half were born incaptivity (n=2). The disease was manifestedafter 2 months to 10 years of captivity. Inone case (n=1), the animal presented withacute incontinence, which eventually resultedin death due to bladder wall perforation bya single pointed calculus with 4 cm in lengthby 1.5 cm in width (Figure 1). In two cases(n=2), recourse to surgery revealed similarclinical features that were evidently chronic,with urinary tract infection, concurrentformation of several uroliths of varioussizes, and irreversible damage makingeuthanasia unavoidable (Figure 2). One ofthe animals (n=1) has survived and is nowundergoing treatment at the BreedingCompound. The main clinical symptomsfound were abdominal distension (n=3),

recurrent urinary tract infections (n=3), painupon abdominal palpation (n=3), difficultyurinating (n=4), polacyuria (n=3), hematuria(n=2), anorexia (n=2), dehydration (n=2),and urinary tenesmus coming to anuria dueto urethra obstruction by calculi (n=2).Radiological examination of three animalsdetected bladder distension and the presenceof many radio-opaque uroliths in thebladder lumen of two animals (n=2).Uroliths found in three animals displayed arounded shape, varying sizes and a yellowishcolor. Diffraction analysis of the urolithsshowed they were made up of CaH2P2O7 -calcium acid pyrophosphate and

Figura 1 - Bladder wall perforation by a single pointedcalculus with 4 cm in length by 1,5 cm inwidth found in a maned wolf (Chrysocyonbrachyurus), during postmortem examinationat the Captive Breeding Compound, Araxá –MG – Brazil. The stone was composed byMgNH4PO4.6H20 - hydrous magnesiumammonium phosphate with traces (1%) ofKCaPO4 – potassium calcium phosphate

Figura 2 - Several stones encrusted in the bladder wallfound in a maned wolf (Chrysocyonbrachyurus) during postmortem examinationat the Captive Breeding Compound, Araxá –MG – Brazil. The stones were composed byCaH2P2O7 - calcium acid pyrophosphateand MnFe2(PO4)2(OH).2H2O - basic hydrousmanganese phosphate

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MnFe2(PO4)2(OH).2H2O - basic hydrousmanganese phosphate (n=1) andMgNH4PO4.6H20 - hydrous magnesiumammonium phosphate with traces (1%) ofKCaPO4 – potassium calcium phosphate(n=1). Electron microscopy showed thaturoliths consisted of crystals with mineralphosphorus, potassium and magnesium(n=2) predominating in their composition(Figures 3 and 4). On postmortemexamination, the three deceased animals werefound to have several calculi encrusted in thebladder wall, in addition to a swollen anddistended bladder. In one case, ahistopathological examination of the kidneys

and bladder showed chronic pyelonephritisand a nonspecific chronic inflammatoryprocess with pronounced activity in both themucosa and the wall of the urinary vesicle.

Discussion

In the present study the clinical caseswere observed only in males, suggesting asex-related pattern, possibly due to theanatomy of the maned wolf ’s penile urethra,which is long and narrow and also because

Figura 3 - Scanning electron micrograph (100 X) of theurolith found in one maned wolf(Chyrsocyon brachyurus) during clinicalexamination at the Captive BreedingCompound, Araxá – MG – Brazil. Panoramicview showing the internal part of the urolith,which was composed by crystals. SecundaryElectron (SE), scale bar = 100 um, aceleratingvoltage 25,0 kV

Figura 4 - Graphic of the chemical composition of theuroliths, by scanning electron microscopy(SEM), that micrograph was showed in figure3. The SEM showed that uroliths were madeby phosphorus, magnesium, potassium andcalcium

the maned wolf has a penile bone. Accordingto the literature, an important health problemfor maned wolves is the formation of cystinecalculi leading to the formation of stones inthe kidney, bladder and urethra. A study ofmaned wolves in captivity and in the wildconcluded that 80% of the animals concernedwere capable of excreting cystine and otherdibasic amino acids in their urine. It is believedthat this unusual pattern may be due to ametabolic disturbance of genetic origin.4Urinary calculi composed of cystine werefound in four maned wolves and proved tobe fatal in three of them.5 Mussart andCoppo6 reported finding of six cystinecalculi incrusted in the renal pelvis of andadult Chrysocyon brachyurus whose death waspreceded by respiratory problems. Basicallythree theories have been proposed to explainthe physiopathology of the urolithisis:Precipitation-crystalization theory, Nucleationhypoyhesis and Crystallization inhibitiontheory. Whichever the theory involved inthe physiopathology, an important conditionthat the urine must fulfill is the unstableoversaturation.7 Because urine is commonlysupersaturated, observation of crystals in theurine does not mean the patient is at risk forurolithiasis. Supersaturation of urine depends

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on the amount of the ion ingested andexcreted in the volume of urine produced.8The urine must be oversaturated withminerals and these have to rely on suitablephysical and chemical conditions that shouldfacilitate the precipitation.7 Most stones haveone major crystal component, which can beformed for several possible reasons, suchas unbalanced diet, decreased water intake,modified urine pH, relative lack of inhibitorsof crystallization. For these reasons thesolubility product of a particular crystal maybe exceeded, crystals may form and thesecrystals may aggregate and grow. The mostcommon stones in dogs and cats are struvite,calcium oxalate and calcium phosphate,urate, cystine and silicate.8

In the present study, a calculicomposed by MgNH4PO4.6H2O with tracesof KCaPO4 was formed in one maned wolfand identified as the composition of struvitestones.8 In dogs, struvite urolithiasis ispredominately a disease associated withinfection. Bacteria promote increasedammonium concentration creating a highlyalkaline pH. Alkaline pH with urine saturatedwith ammonium, phosphate and magnesiumions results in nucleation of struvite crystals.9In dogs which struvite stones are formed inspite of the absence of urinary tract infection,predisposing factors include a family historyof struvite stones, a diet based on vegetableproteins and distal renal tubular acidosis.8 Incats, the risk of struvite uroliths increases dueto dietary influences on urinary pH andstone-forming constituents (i.e. magnesium,phosphorus and ammonium) and urinarytract infection are not the driving forcebehind the formation of alkaline urine.9 Thestruvite stones are spherical, ellipsoidal ortetrahedral in shape and may be present insingly or in large numbers of varying sizes.The bladder is the most common site ofstruvite stone formation, although it canoccur at any site in the urinary tract.8

Another calculus composed bycalcium and phosphate and manganesephosphates was found in one maned wolf.Calcium oxalate or calcium phosphate calculiare usually white in colour and very hard.

They often have sharp, jagged edges, maybe single or in multiple number and arefound most often in the bladder and urethra.Urinary tract infection can be a predisposingfactor to calcium oxalate urolithiasis. Alteredcalcium metabolism also may play a role indevelopment of calcium oxalate urolithiasis.8

In the present study it was observedthat as well as occurring in association withrecurrent urinary infections, urolithiasis mayalso have been caused by unsuitable diet,especially in light of the fact that thenutritional requirements for captive manedwolves are unknown.10

The uroliths damage the urinary tractmucous, which generates inflammation(hematuria, pollakiuria, dysuria, stranguria)and it predisposes to the bacterial colonizationand infection of urinary tract. The clinicalsigns depend on the anatomical location,antiquity and physical characteristics of theuroliths precedents from the urethral acutepartial or complete obstruction. The patientscan be asymptomatic when the uroliths arein the unilateral renal pelvis or at the ureters,or to present hematuria and abdominal paincausing often hydronephosis.7 In the presentstudy, the majority of the symptoms wereobserved only in the final clinical stage ofthe disease.

The assessment of uroliths presenceis done by simple radiographic studies orwith contrast.7 Appropriate survey orcontrast radiography or ultrasonographyshould always be performed to localize thesite (s) of obstruction, as well the number,size and surface characteristics of the uroliths.Although survey abdominal radiography willnot detect all uroliths, the majority of thecommon uroliths (struvite, calcium oxalate,cystine) are radiodense to some degree, withthe exception of some urate uroliths that areradiolucent.11 According to Gallatti andIwasaki12, the positive contrast-cystographyis more efficient in detecting mucosal surfaceirregularity of the bladder, bladderdisplacement and intraluminal structures,except calculi, and the ultrasonography ismore efficient in detecting uroliths andbladder wall thickening. The urinalysis is a

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useful tool for the diagnosis of crystalluria,to determine the type of mineral thatsaturates the urine and represents part of thecomposition of the urolith. Thedetermination of the pH though the urinalysisis also important for differential diagnosisof the uroliths, as well as some other generalfinds as hematuria or pyuria.7 Calculiscomposed by struvite, calcium carbonate,calcium phosphate and urate are moresoluble in acidic urine (pH < ~ 6.8); uricacid and cystine are more soluble in alkalineurine (pH >~7.0); and calcium oxalate areminimal affected by urine pH.8 Themacroscopic morphology is too diverse asfor to allow a diagnosis based on the physicalaspects of the stones. It is necessary to carryout a correct analysis of each calculi todetermine the types of mineral of whichthey are constituted to establish the treatmentfor the animal.7

The treatment of urolithiasis is basedon the relief of urinary tract obstruction andreestablishment of urine flow.8 Urethralobstruction is a life–threatening situation andcan be fatal due to renal dysfunction andretention of metabolic wastes, especiallypotassium and metabolic acids.11 Strategiesfor treating struvite stones in dogs involvetreating the urinary tract infection inconjunction with physical or dietary removalof existing stones.9 The use of urinaryacidifiers to maintain urine pH in the rangeof 6.0-6.5 has been suggested in dogsbecause struvite and hydroxyapatite are mostsoluble in acidic urine.8 In dogs, the dietarychanges for struvite prevention includespromotion of an acid urine (pH 6.5)together with phosporus and magnesiumrestriction.9 Surgery is required to removecalcium oxalate stones in dogs and cats. Pos-operatively, a diet low in calcium and oxalate

should be fed. Dietary phosphorus shouldnot be restricted because reducedphosphorus could result in increasedactivation of vitamin D3 to calcitriol by 1-a-hidroxylase in the kidney and causeincreased intestinal absorption of calcium.Also, urinary pyrophosphate may functionas an inhibitor of calcium oxalate formation.Dietary magnesium should not be restrictedeither, because it may serve as an inhibitorof calcium oxalate formation.8

Conclusion and Recommendations

This is the first time any scientificresearch has demonstrated the occurrenceof urolithiasis associated with uroliths ofmineral composition based on phosphate,potassium and magnesium in captive manedwolves. The only cases of urolithiasis inmaned wolves documented hitherto werecystine-related. Moreover, analysis of theresults showed a high rate of mortalitycorrelated with urolithiasis in this species,pointing to a need to develop a protocolinvolving periodic clinical assessmentsupplemented by biochemical tests anddiagnostic imaging to detect early onset ofthe disease for providing suitable treatmentin time and prevent complications,which if not treated in a timely andadequate manner may result in death.Therapeutic measures for urolithiasis involveappropriate nutritional management, use ofmedication and, in some cases, specificsurgical procedures. Diagnosis and treatmentof the diseases to which wild animalsare subject when in captivity areextremely important for maintenance andreproduction of these species with aview to their conservation in theenvironment.

Urolitiase em lobo guara (Chrysocyon brachyurus): Avaliação de quatro

casos clínicos em cativeiro

Resumo

Foram estudados quatro casos de urolitíase em lobos guarás(Chrysocyon brachyurus), que ocorreram no período de 1989 a 2004, de

Palavras-chave:Lobo Guará. Urolitíase.Composição mineral deurólitos.Sintomas clínicos daurolitíase.

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animais mantidos em cativeiro. Os casos clínicos ocorreram em quatromachos adultos. O tempo de cativeiro para a manifestação da doençanos animais variou de dois meses a 10 anos. Os principais sintomasclínicos apresentados foram distensão abdominal, infecções recorrentesdo trato urinário, dor à palpação abdominal, dificuldade em urinar,polaciúria, hematúria, anorexia, desidratação e tenesmo urinário comevolução para anúria em decorrência da obstrução da uretra por cálculos.Ao exame radiológico detectou-se distenção da bexiga e a presença deinúmero urólitos radiopacos no lúmen do órgão. As análisesdifratométricas dos urólitos revelaram que eles eram compostos dePirofostato Ácido de Cálcio e Fosfato Básico de Manganês Hidratado(n=1)) e Fosfato de Amônio Magnésio Hidratado com traços deFosfato de Potássio e Cálcio (n=1). A microscopia eletrônica revelouque os urólitos eram formados por cristais, com predominância dosminerais de fósforo, potássio e magnésio (n=2) em sua composição.O presente estudo demonstrou, de forma inédita, a ocorrência deurolitíase associada a urólitos de composição mineral a base de fosfato,potássio e magnésio, em lobos guarás cativos. Até então, só foramdocumentados casos de urolitíase em lobos guarás relacionados àcistina. As medidas terapêuticas da urolitíase envolvem manejonutricional adequado, utilização de medicamentos e, em alguns casos,cirurgias específicas. O diagnóstico e tratamento das doenças queacometem animais silvestres em cativeiro são de extrema importânciapara a manutenção e reprodução dessas espécies, visando à suaconservação no meio ambiente.

References

1 FLETCHALL, N. B. História natural. In: FLETCHALL,N. B.; RODDEN, M.; TAYLOR, S. (Ed.). Manual demanejo do Lobo Guará Chrysocyon brachyurus. SãoPaulo; CEPREM, 2000. cap.1.

2 DIETZ, J. M. Ecology and Social Organization of theManed Wolf (Chrysocyon brachyurus). [s.l.:s.n.](Smithsonian Contributions To Zoology, n. 392). 1984.

3 CARLTONN, W. W. Patologia veterinária especialde Thomson. 2a. ed. Porto Alegre: Art. Med, 1998. p.260-262.

4 ALLEN, M. E. Maned wolf nutritional management.In: FLETCHALL, N. B.; RODDEN, M.; TAYLOR, S.(Ed.). Husbandry manual for the maned wolfChrysocyon brachyurus. [s.l.]: American Association ofZoos and Aquariums, 1995.

5 BOOVE, K. C. et al. Cystinuria in the maned wolf ofSouth America. Science, v. 212, p. 919-920, 1981.

6 MUSSART, N. B.; COPPO, J. A. Cystine nephrolitiasisin an endangered canid, Chysocyon brachyuurus(Carnivora: canidae). Revista Biológica Tropical, v. 47,p. 623-625, 1999.

7 CARAZA, J. D. A. Deciding the medical managementof the patient with urolithiasis. In: WORLD SMALLANIMAL VETERINARY ASSOCIATION. 30., 2005,Mexico City. Proceedings…

8 BUFFINGTON, T. Nutrition and urolithiasis. In:WORLD SMALL ANIMAL VETERINARY

ASSOCIATION. 29., 2004, Rhodes, Greece.Proceedings…

9 KIRK, C. A.; BIOURGE, V. C. Managing struvite /oxalate rolithiasis: point / counterpoint. In: NAVCProceedings 2006. North American VeterinaryConference (Ed.). Publisher: NAVC (www.tnavc.org).Internet Publisher: International Veterinary InformationService, Ithaca NY (www.ivis.org), last updated: 11 jan2006.

10 PESSUTTI, C.; SANTIAGO, M. E. B.; OLIVEIRA, L.T. F. Order Carnivora, Family Canidae (Dogs, Fox,Maned Wolves). In: FOWLER, M. E.; CUBAS, Z. S.Biology, medicine, and surgery of South American wildanimals. 1a. ed. USA: Iowa State University Press, 2001.cap. 26, p. 282.

11 SANDERSON, S. Urethral obstruction: techniquesto relieve obstruction and management of the patient.In: WORLD SMALL ANIMAL VETERINARYASSOCIATION. 30., 2005, Mexico City. Proceedings…

12 GALLATTI, L. B.; IWASAKI, M. Comparison ofultrasonography and positive contrast cystography fordetection of urinary bladder disorders in dogs. Braz. J.Vet. Res. Anim. Sci. [online], v. 41, n 1, p. 40-46, 2004.Available from: <http://www.scielo.br/sc ie lo .php?sc r ip t=sc i_a r t t ex t&p id=S1413-95962004000100007&lng=en&nrm=iso>. ISSN1413-9596>. Cited 2007 may 4.

13 BUSH, M.; BOOVE, K. C. Cystinuria in the manedwolf. Journal of American Veterinarian MedicineAssociation, v. 9, p. 1159-1162, 1978.

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