Renal histopathological changes in dogs naturally infected with Ehrlichia canis

Renal involvement in Canine Monocytic Ehrlichiosis (CME) has been demonstrated in chronic cases without histopathological classification of patterns of glomerulopathy. Thus, in this study we proposed to evaluate the histopathological pattern, focusing on the types of glomerulonephritis in kidneys of dogs naturally infected with Ehrlichia canis.Twelve dogs naturally infected with E. canis and six healthy dogs were used. After clinical evaluation and diagnostic confirmation, the animals were euthanized and kidney fragments were obtained for histopathological examination, including hematoxylin and eosin (HE), Massons trichrome, periodic acid-Schiff (PAS), periodic acid-methenamine silver (PAMS) and Congo red stain. Histopathological analysis of dogs with CME demonstrated that major lesions were present in the glomerulus and tubulointerstitial region in 100% of cases. The type of glomerular injury was membranoproliferative in 83.33%, and proliferative in 16.67%. Interstitial nephritis was present in the cortical region of all infected dogs. Minimal to marked lymphohistioplasmacytic inflammatory infiltrate was present in the interstitial, perivascular and periglomerular areas. Differential count of inflammatory cells indicated that lymphocytes predominated in comparison to plasma cells and histiocytes. Interstitial fibrosis and hyaline casts of lower intensity were observed. There was a negative correlation between serum albumin levels and severity of glomerulopathy. In conclusion, membranoproliferative glomerulopathy and interstitial nephritis are the major renal lesions in CME. It has been suggested that the presence of inflammatory infiltrates rich inlymphocytes indicates participation of these infiltrates in the immunopathogenesis of renal lesion in dogs with CME. Furthermore, hypoalbuminemia also seems be a marker of renal damage in dogs infected with E. canis.

Renal histopathological changes in dogs naturally infected with Ehrlichia canis

Renal involvement in Canine Monocytic Ehrlichiosis (CME) has been demonstrated in chronic cases without histopathological classification of patterns of glomerulopathy. Thus, in this study we proposed to evaluate the histopathological pattern, focusing on the types of glomerulonephritis in kidneys of dogs naturally infected with Ehrlichia canis.Twelve dogs naturally infected with E. canis and six healthy dogs were used. After clinical evaluation and diagnostic confirmation, the animals were euthanized and kidney fragments were obtained for histopathological examination, including hematoxylin and eosin (HE), Massons trichrome, periodic acid-Schiff (PAS), periodic acid-methenamine silver (PAMS) and Congo red stain. Histopathological analysis of dogs with CME demonstrated that major lesions were present in the glomerulus and tubulointerstitial region in 100% of cases. The type of glomerular injury was membranoproliferative in 83.33%, and proliferative in 16.67%. Interstitial nephritis was present in the cortical region of all infected dogs. Minimal to marked lymphohistioplasmacytic inflammatory infiltrate was present in the interstitial, perivascular and periglomerular areas. Differential count of inflammatory cells indicated that lymphocytes predominated in comparison to plasma cells and histiocytes. Interstitial fibrosis and hyaline casts of lower intensity were observed. There was a negative correlation between serum albumin levels and severity of glomerulopathy. In conclusion, membranoproliferative glomerulopathy and interstitial nephritis are the major renal lesions in CME. It has been suggested that the presence of inflammatory infiltrates rich inlymphocytes indicates participation of these infiltrates in the immunopathogenesis of renal lesion in dogs with CME. Furthermore, hypoalbuminemia also seems be a marker of renal damage in dogs infected with E. canis.(AU)

Effect of administering a diet contamined with fumonisins on the kidneys of wistar rats / Efeito da administração de ração contaminada com a micotoxina fumonisinas sobre os rins de ratos wistar

Fumonisins (FBs) are mycotoxins produced by Fusarium molds. Several works have shown contamination of maize by this toxin. Fumonisin B1 (FB-1) is found in greatest proportion (about 70%), resistant to several industrialization processes. In that context, the objective of this work was to analyze the effect of administering a diet contaminated with FB-1 on the morphophysiology of the kidneys of 21-day old male Wistar rats. The animals were divided into 2 groups: G0 (with animals receiving feed free of FBs) and G6 (6mg of FB1 kg-1 of feed). The diet was administered during 42 days. After that period, the animals were placed in metabolic cages for urine collection, blood was collected for analysis of plasma creatinine, and the kidneys were fixed and stained with Masson"s trichrome. We observed that FB1 administration did not affect feed intake, body weight gain and animal growth. The normal levels of plasma creatinine suggest that the toxin did not lead to glomerular lesion. There was also no change in water intake, osmolarity and excretion of sodium in urine. However, there was a significant increase in urine volume and potassium excretion in urine, with mild tubulointerstitial changes in the outer cortex for the group receiving the mycotoxin.(AU)

Fumonisinas (FBs) sمo micotoxinas produzidas por fungos do gênero Fusarium. Diversos trabalhos demonstraram a contaminaçمo do milho por essa toxina. A fumonisina B1 (FB-1) é encontrada em maior proporçمo (cerca de 70%), sendo resistente a vلrios processos de industrializaçمo. De acordo com este contexto, o trabalho em foco teve como objetivo analisar o efeito da administraçمo de dieta contaminada com FB-1 sobre a morfofisiologia renal de ratos Wistar machos, com 21 dias de idade. Os animais foram divididos em 2 grupos: G0 (raçمo isenta de FBs) e G6 (alimentados com 6mg de FB1 kg-1 de raçمo). A dieta foi administrada por 42 dias. Apَs esse perيodo, os animais foram colocados em gaiolas metabَlicas para coleta da urina, o sangue foi coletado para anلlise da creatinina plasmلtica, e os rins fixados e corados pelo Tricrômico de Masson. Observou-se que a administraçمo de FB1 nمo afetou o consumo de raçمo, o ganho de peso e crescimento dos animais. A normalidade nos nيveis da creatinina plasmلtica sugere que a toxina nمo induziu lesمo glomerular. Nمo houve alteraçمo na quantidade de لgua ingerida, na osmolaridade e na excreçمo urinلria do sَdio. No entanto houve aumento significativo no volume urinلrio e na excreçمo urinلria do potلssio e presença de alteraçُes tubulointersticiais de intensidade leve no cَrtex externo, no grupo que recebeu a micotoxina.(AU)

O papel de imunoglobulinas na nefropatia da leptospirose em suínos / The role of immunoglobulins in nephropathy of leptospirosis in pigs

A leptospirose é uma antropozoonose endêmica em todo o mundo, que afeta o homem e várias espécies de animais domésticos e silvestres. No início da infecção há produção de IgM para o controle da infecção e após alguns dias, IgG são produzidas e provocam lise das leptospiras circulantes. Objetivou-se neste estudo identificar depósitos de antígeno de leptospiras e imunoglobulinas no tecido renal, para avaliar o papel de imunoglobulinas na patogênese da nefropatia da leptospirose em suínos. Foram colhidas 139 amostras de sangue e rim de suínos das cidades de Teresina/PI e Timon/MA, que foram avaliadas pela SAM, imunoistoquímica e PCR. Nefrite intersticial, fibrose, vasculite, tumefação do tufo glomerular e hipercelularidade difusa foram as principais alterações histopatológicas encontradas. A imunoistoquímica detectou antígeno de leptospira em 60 suínos. Depósitos de IgG, IgM e IgA foram observados no endotélio de capilares glomerulares, dos capilares intertubulares e na cápsula de Bowman, com marcação focal, difusa, global e segmentar. A deposição de IgM e IgA foi significantemente maior nos suínos infectados. Estranhamente depósitos de IgG foi significantemente maior nos suínos não infectados, onde não havia presença de antígeno de leptospiras e nem lesão túbulo-intersticial. Concluímos que antígeno de leptospiras no rim de suínos está relacionado a depósitos de IgM e IgA mas não a depósitos de IgG.(AU)

Leptospirosis is an endemic worldwide anthropozoonosis, affecting humans and several species of domestic and wild animals. At the beginning of infection is the production of IgM to control the infection and after a few days, IgG is produced and cause lysis of circulating leptospires. The objective of this study was to identify deposits of immunoglobulins and antigens of leptospires in kidney tissue, to assess the role of immunoglobulins in the pathogenesis of leptospirosis nephropathy in pigs. We collected 139 blood samples and kidney of pigs from the cities of Timon/MA and Teresina/PI, to be evaluated by SAM, immunohistochemistry and PCR. Interstitial nephritis, fibrosis, vasculitis; swollen glomeruli hypercellularity and diffuse in a pig were main pathological changes found. Immunohistochemistry leptospira antigen detected in 60 pigs. Deposits of IgG, IgM and IgA were observed in the endothelium of glomerular capillaries, the capillaries intertubulares and the Bowman's capsule, marked focal, diffuse, global and segmental. The deposition of IgM and IgA was significantly higher in infected pigs, strangely deposits of IgG was significantly higher in non-infected pigs, where there was no presence of antigen leptospires nor tubulointerstitial injury. We conclude that Leptospira antigen in porcine kidney relates to deposits of IgM and IgA but not IgG deposits.(AU)

INVESTIGAÇÃO MOLECULAR DA PRESENÇA DE PARAMYXOVÍRUS FELINO EM TECIDO RENAL DE GATOS DOMÉSTICOS DE CUIABÁ, MATO GROSSO

O morbillivírus felino (FeMV) é um vírus detectado recentemente em amostras de urina e tecido renal de gatos domésticos em várias regiões geográficas do mundo. Sua identificação tem sido justificada pela sua associação com nefrite tubulointersticial, principal diagnóstico morfológico da doença renal crônica (DRC) em gatos. A DRC é a afecção mais comum de gatos geriátricos, levando a uma série de alterações que são importantes causas de morbidade e mortalidade para os gatos. Devido à dificuldade de se descobrir a causa etiológica para o desenvolvimento da doença, é de extrema importância identificar possíveis fatores de risco. O objetivo deste trabalho foi a detecção da infecção por paramyxovírus felino em tecido renal de gatos domésticos do município de Cuiabá, que vieram a óbito por diversas causas, assim como associar a infecção pelo vírus com a DRC. Para tal, sessenta e dois gatos que vieram a óbito no HOVET da UNIC e outras clínicas de Cuiabá foram submetidos à necropsia, onde fragmentos renais e hepáticos foram coletados para avaliação molecular, utilizando RT-seminested PCR e a avaliação histopatológica renal dos mesmos animais. Os produtos da PCR foram purificados e sequenciados utilizando os kits PureLink Quick Gel Extraction and PCR Purification Combo, e Terminator V.3.1 cycle sequencing. Dos sessenta e dois gatos necropsiados, apenas cinco tinham a presença do genoma viral em tecido renal, sendo que um destes gatos tinha também a presença do vírus em amostra hepática, mostrando uma baixa prevalência do FeMV. A avaliação histopatológica mostrou que a infecção pelo FeMV esta associado com inflamação intersticial, mas não com DRC.

Feline morbillivirus (FeMV) is a recently detected virus in samples of urine and renal tissue from domestic cats in various geographic regions of the world. Its identification has been justified by its associating with tubulointerstitial nephritis, the main morphological diagnosis of chronic kidney disease (CKD) in cats. CKD is the most common condition of geriatric cats, leading to a number of changes that are important causes of morbidity and mortality for cats. Because of the difficulty in defining the etiological cause for the development of the disease, it is extremely important to identify possible risk factors. The aim of this study was to detect the feline paramyxovirus infection of renal tissue in domestic cats of the city of Cuiabá, which died due to several causes, as well as to attempt to associate this viral infection with CKD. Sixty-two cats that died in HOVET of UNIC and other clinics in Cuiabá were submitted to necropsy, where renal and hepatic fragments were collected for molecular evaluation using RT-seminested PCR, histopathological evaluation. PCR products were purified and sequenced using the PureLink Quick Gel Extraction and PCR Purification Combo kits and Terminator V.3.1 cycle sequencing kits. Of the sixty-two necropsied cats only five had the presence of the viral genome in renal tissue, one of which had the presence of the virus in a liver sample as well, demonstrating a low prevalence of FeMV. Histopathological evaluation showed that FeMV infection is associated with interstitial inflammation, but not with CKD.

Aspectos anatomopatológicos da leptospirose em cães: 53 casos (1965-2011) / Pathological aspects of leptospirosis in dogs: 53 cases (1965-2011)

Os aspectos anatomopatológicos da leptospirose foram estudados em 53 cães que tiveram diagnóstico definitivo confirmado por imuno-histoquímica do tecido renal. Na necropsia, as principais lesões observadas incluíram icterícia (79,2%) e hemorragia (75,5%), principalmente no pulmão (56,6%). Alterações macroscópicas hepáticas (56,6%) e renais (50,9%) foram frequentes e caracterizavam-se principalmente por descolorações (30,2% e 32,1% respectivamente), acentuação do padrão lobular hepático (26,4%) e estriações brancas na superfície de corte dos rins (22,6%). Lesões extrarrenais de uremia ocorreram na metade dos casos (50,9%). Hepatomegalia (11,3%), nefromegalia (9,4%) e irregularidade da superfície capsular dos rins (3,8%) foram menos comuns. Na histologia dos rins (n=53), as lesões encontradas (98,1%) foram quase que exclusivamente agudas ou subagudas (96,2%) e caracterizavam-se por graus variados de nefrose tubular (86,8%) e nefrite intersticial não supurativa (60,4%), com evidente dissociação degenerativo-inflamatória. Na histologia do fígado (n=42), as lesões encontradas (97,6%) eram constituídas principalmente por dissociação dos cordões de hepatócitos (78,6%), colestase intra-canalicular (33,3%) e necrose hepática (31%). Lesões reativas, como hipertrofia das células de Kupffer, leucocitostase sinusoidal e infiltrado inflamatório mononuclear nos espaços porta, foram vistas em muitos casos (42,8%). Na histologia do pulmão (n=28), hemorragia (85,7%) e edema (57,1%) alveolares foram muito prevalentes. Neutrófilos e macrófagos nos espaços alveolares (35,7%) e neutrófilos no interior de pequenos vasos pulmonares (17,9%) também foram achados frequentes. Os resultados aqui demonstrados devem servir de alerta aos patologistas veterinários brasileiros, pois a apresentação anatomopatológica da leptospirose canina em nossa região (Região Central do Rio Grande do Sul, Brasil) não se modificou nos últimos 50 anos, mantendo-se semelhante àquela descrita internacionalmente até a década de 1980, mas muito diferente do que é atualmente reconhecido para os Estados Unidos, o Canadá e parte da Europa Ocidental. Recomendamos que os critérios histopatológicos para o diagnóstico da leptospirose canina devem incluir a presença concomitante de nefrite tubulointersticial aguda ou subaguda, hepatite reativa não específica e lesão alveolar difusa, incluindo hemorragia alveolar difusa com capilarite, em um cão que durante a necropsia demonstre icterícia, hemorragias e lesões extrarrenais de uremia na ausência de esplenomegalia.(AU)

The pathological aspects of canine leptospirosis were studied in 53 dogs with a conclusive diagnosis of the disease, as confirmed by immunohistochemistry on renal tissue. Main necropsy lesions included icterus (79.2%) and hemorrhage (75.5%), mainly in the lungs (56.6%). Gross hepatic (56.6%) and renal (50.9%) changes were frequently found and were characterized mainly by discoloration (respectively 30.2% and 32.1%), accentuation of hepatic lobular pattern (26.4%) and white streaks in the cut surface of kidneys (22.6%). Extrarenal lesions secondary to uremia occurred in half of the cases (50.9%). Enlarged livers (11.3%), and kidneys (9.4%), and rough renal capsular surfaces (3.8%) were less common findings. In the histopathology of the kidneys (n=53), the encountered lesions (98.1%) were almost exclusively acute or subacute (96.2%) and were characterized by varying degrees of tubular nephrosis (86.8%) and non-suppurative interstitial nephritis (60.4%), with evident degenerative-inflammatory dissociation. In the histopathology of the liver (n=42), the encountered lesions (97.6%) consisted mainly of hepatocellular dissociation (78.6%), intracanalicular cholestasis (33.3%) and hepatocellular necrosis (31%). Reactive lesions, such as Kupffer cell hypertrophy, sinusoidal leucocytostasis and inflammatory mononuclear infiltrate within portal triads were observed in several cases (42.8%). In the histopathology of the lung (n=28), alveolar hemorrhage (85.7%) and edema (57.1%) were rather frequent lesions. Neutrophils and macrophages in the alveolar spaces (35.7%) and neutrophils within small pulmonary vessels (17.9%) were also frequent findings. The findings stemming from the current study should serve as an alert for Brazilian veterinary pathologists, since the pathological presentations of canine leptospirosis in this region (Central Region of the State of Rio Grande do Sul, Brazil) did not change in the last 50 years, and is still similar to that described worldwide up to the decade of 1980's, but rather different from that currently recognized in the United States, Canada and part of West Europe. We recommend that the histopathological criteria for the diagnosis of canine leptospirosis should include the concomitant occurrence of acute or subacute tubulointerstitial nephritis, non specific reactive hepatitis and diffuse alveolar damage, including diffuse alveolar hemorrhage with capillaritis, in a dog which at necropsy had presented icterus, hemorrhage and extrarenal lesions of uremia without splenomegaly.(AU)

Effect of sirolimus on renal injury induced by bile duct ligation in rats / Efeito do sirolimo na lesão renal induzida pela ligadura do ducto biliar em ratos

PURPOSE: To evaluate the effects of sirolimus (SRL) on renal injury in rats with bile duct ligation. METHODS: A total of 21 male Sprague-Dawley rats weighing 220-260g were used. Group 1 (Sham-control, n=7) rats were undergone laparotomy alone and bile duct was just dissected from the surrounding tissue. Group 2 rats (BDL/Untreated, n=7) were subjected to bile duct ligation and no drug was applied. Group 3 rats (BDL/SRL, n =7) received a daily dose of sirolimus (0.5 mgÀday-1xkg-1 dissolved 1 ml in saline) by orogastric tube for 14 days after BDL. At the end of the two-week period, biochemical and histological evaluation were processed. RESULTS: AST, ALT, AP and TB levels values were decreased in group 3 when compared to group 2. There was no significant difference in serum levels of BUN and creatinine among all the experimental groups. Histological evaluation of the liver of BDL/Untreated group rats demonstrated marked portal fibrosis and signs of major bile duct obstruction with prominent portal and lobular inflammation. In BDL/SRL group, moderate damage was seen. Tubular injury scores were higher in the BDL subgroups; however, group 3 rats showed considerably fewer lesions in the tubules and interstitium compared to the group 2 rats. In group 2 animals, in the epithelial cells of proximal tubules presented vacuoles and hydropic changes, atrophy and inflammatory cell infiltrate in the medullar interstitium. CONCLUSIONS: Sirolimus decreased tubulointerstitial lesions in kidney induced by bile duct ligation in rats. The improve effects of sirolimus on renal morphology can be due to improved liver function or due to direct action on the kidney.(AU)

OBJETIVO: Investigar os efeitos do sirolimo (SRL) na lesão renal induzida pela ligadura do ducto biliar em ratos. MÉTODOS: Foram utilizados 21 ratos Sprague-Dawley pesando entre 220-260 g. Grupo 1 (Sham-controle, n=7) submetidos a laparotomia e o ducto biliar dissecado do tecido circundante. Grupo 2 (BDL/Não tratado, n=7) foram submetidos a ligadura do ducto biliar e nenhuma droga foi aplicada. Grupo 3 (BDL/SRL, n=7) receberam dose diária de sirolimo (0,5 mg dia-1xkg-1 dissolvido em 1 ml em solução salina) por tubo orogástrico por 14 dias após BDL. Após duas semanas era realizada avaliação bioquímica e histológica. RESULTADOS: Níveis de AST, ALT, AP e TB estavam diminuídos no grupo 3 comparado ao grupo 2. Não houve diferença significante nos níveis séricos de BUN e creatinina em todos os grupos. Observou-se na avaliação histológica evidente fibrose portal e sinais de obstrução do ducto biliar com evidente inflamação portal e lobular. No grupo BDL/SRL verificou-se dano moderado. Lesão tubular foi maior nos subgrupos BDL; entretanto, o grupo 3 mostrou considerável menos lesões nos túbulos e interstício comparados ao grupo 2. No grupo 2 as células epiteliais dos túbulos proximais apresentaram vacúolos e alterações hidrópicas, atrofia e infiltrado celular inflamatório no interstício medular. CONCLUSÕES: Sirolimo diminuiu lesões tubulointersticial no rim induzida pela ligadura do ducto biliar em ratos. Os efeitos benéficos do sirolimo na morfologia renal pode ser devida à melhora da função hepática ou devido à ação direta no rim.(AU)

Aspectos anatomopatológicos da leptospirose em cães / Pathological aspects of leptospirosis in dogs

Leptospirose é uma zoonose causada por espiroquetas do gênero Leptospira e constitui uma das mais importantes doenças de distribuição mundial. Embora leptospirose seja reconhecidamente uma das doenças infecciosas mais frequentemente descritas em cães, não existem critérios morfológicos para a realização do diagnóstico definitivo com base apenas na necropsia. Assim, o objetivo principal deste trabalho é estabelecer critérios anatomopatológicos para o diagnóstico da leptospirose. Os arquivos de necropsia do Laboratório de Patologia Veterinária da Universidade Federal de Santa Maria (LPV-UFSM) foram acessados e todos os casos diagnosticados como leptospirose entre os anos de 1965 e 2011 foram revisados (n=135). Foi realizada imuno-histoquímica para confirmação do diagnóstico definitivo apenas nos casos em que o tecido renal foi considerado viável em quantidade e qualidade (n=79). Os casos positivos foram identificados e correspondem aos resultados aqui demonstrados (n=53). Na necropsia, as principais lesões observadas incluíram icterícia (79,2%) e hemorragia (75,5%), principalmente no pulmão (56,6%). Alterações macroscópicas hepáticas (56,6%) e renais (50,9%) foram frequentes e caracterizavam-se principalmente por descolorações (30,2% e 32,1% respectivamente), acentuação do padrão lobular hepático (26,4%) e estriações brancas na superfície de corte dos rins (22,6%). Lesões extrarrenais de uremia ocorreram na metade dos casos (50,9%). Hepatomegalia (11,3%), nefromegalia (9,4%) e irregularidade da superfície capsular dos rins (3,8%) foram menos comuns. Na histologia dos rins (n=53), as lesões encontradas (98,1%) foram quase que exclusivamente agudas ou subagudas (96,2%) e caracterizavam-se por graus variados nefrose tubular (86,8%) e nefrite intersticial não supurativa (60,4%), com evidente dissociação degenerativo-inflamatória. Na histologia do fígado (n= 42), as lesões encontradas (97,6%) eram constituídas principalmente por dissociação dos cordões de hepatócitos (78,6%), colestase intracanalicular (33,3%) e necrose hepática (31%). Lesões reativas, como hipertrofia das células de Kupffer, leucocitostase sinusoidal e infiltrado inflamatório mononuclear nos espaços porta, foram vistas em muitos casos (42,8%). Na histologia do pulmão (n=28), hemorragia (85,7%) e edema (57,1%) alveolares foram muito prevalentes. Neutrófilos e macrófagos nos espaços alveolares (35,7%) e neutrófilos no interior de pequenos vasos pulmonares (17,9%) também foram achados frequentes. Os resultados aqui demonstrados devem servir de alerta aos patologistas veterinários brasileiros, pois a apresentação anatomopatológica da leptospirose canina em nossa região (Região Central do Rio Grande do Sul, Brasil) não se modificou nos últimos 50 anos, mantendo-se semelhante àquela descrita internacionalmente até a década de 1980, mas muito diferente do que é atualmente reconhecido para os Estados Unidos, o Canadá e parte da Europa Ocidental. Recomendamos que os critérios histopatológicos para o diagnóstico da leptospirose canina devem incluir a presença concomitante de nefrite tubulointersticial aguda ou subaguda, hepatite reativa não específica e lesão alveolar difusa, incluindo hemorragia alveolar difusa com capilarite, em cães que durante a necropsia demonstrem icterícia, hemorragias e lesões extrarrenais de uremia na ausência de esplenomegalia

Leptospirosis is a zoonotic disease caused by spirochetes of the genus Leptospira and it is one of the most important diseases with worldwide distribution. Although leptospirosis is recognized as one of the most commonly reported infectious diseases in dogs, there are no morphological criteria to achieve a definitive diagnosis based only on necropsy lesions. The objective of this study is to establish criteria for the pathological diagnosis of leptospirosis. The necropsy files of the Laboratório de Patologia Veterinária (LPV) of the Universidade Federal de Santa Maria (UFSM) were acessed and all cases diagnosed as leptospirosis between the years of 1965 and 2011 (n=135) were reviewed. Immunohistochemistry for confirmation of definitive diagnosis was performed only in those cases where the kidney tissue was considered viable in quantity and quality (n=79). The positive cases were identified and correspond to the results shown here (n=53). Main necropsy lesions included icterus (79.2%) and hemorrhage (75.5%), mainly in the lungs (56.6%). Gross hepatic (56.6%) and renal (50.9%) changes were frequently found and were characterized mainly by discoloration (respectively 30.2% and 32.1%), accentuation of hepatic lobular pattern (26.4%) and white streaks in the cut surface of kidneys (22.6%). Extrarenal lesions secondary to uremia occurred in half of the cases (50.9%). Enlarged livers (11.3%), and kidneys (9.4%), and rough renal capsular surfaces (3.8%) were less common findings. In the histopathology of the kidneys (n=53), the encountered lesions (98.1%) were almost exclusively acute or subacute (96.2%) and were characterized by varying degrees of tubular nephrosis (86.8%) and non-suppurative interstitial nephritis (60.4%), with evident degenerativeinflammatory dissociation. In the histopathology of the liver (n=42), the encountered lesions (97.6%) consisted mainly of hepatocellular dissociation (78.6%), intracanalicular cholestasis (33.3%) and hepatocellular necrosis (31%). Reactive lesions, such as Kupffer cell hypertrophy, sinusoidal leucocytostasis and inflammatory mononuclear infiltrate within portal triads were observed in several cases (42.8%). In the histopathology of the lung (n=28), alveolar hemorrhage (85.7%) and edema (57.1%) were rather frequent lesions. Neutrophils and macrophages in the alveolar spaces (35.7%) and neutrophils within small pulmonary vessels (17.9%) were also frequent findings. The findings stemming from the current study should serve as an alert for Brazilian veterinary pathologists, since the pathological presentations of canine leptospirosis in this region (Central Region of the State of Rio Grande do Sul, Brazil) did not change in the last 50 years, and is still similar to that described worldwide up to the decade of 1980s, but rather different from that currently recognized in the United States, Canada and part of West Europe. We recommend that the histopathological criteria for the diagnosis of canine leptospirosis should include the concomitant occurrence of acute or subacute tubulointerstitial nephritis, non specific reactive hepatitis and diffuse alveolar damage, including diffuse alveolar hemorrhage with capillaritis, in dogs which at necropsy had presented icterus, hemorrhage and extrarenal lesions of uremia without splenomegaly