CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / IntroduÃÃo. A leptospirose à uma doenÃa endÃmica no Nordeste, sendo caracterizada por complicaÃÃes potencialmente fatais como a lesÃo renal aguda (LRA). O objetivo deste estudo foi avaliar as manifestaÃÃes clÃnicas, a classificaÃÃo da LRA e os fatores de risco para Ãbito em pacientes com a forma grave de leptospirose. MÃtodos. Foi realizado estudo retrospectivo em pacientes com a forma grave de leptospirose internados em hospitais terciÃrios na cidade de Fortaleza, nordeste do Brasil. Foram avaliadas as manifestaÃÃes clÃnicas, os exames laboratoriais na admissÃo e durante a internaÃÃo e o tratamento instituÃdo. LRA foi definida de acordo com as classificaÃÃes RIFLE e AKIN, sendo comparados os pacientes nas diferentes classes. Foram comparados os pacientes que usaram com aqueles que nÃo usaram penicilina, assim como os pacientes que sobreviveram com os que foram a Ãbito. AnÃlises univariada e multivariada foram usadas para a investigaÃÃo dos fatores de risco para Ãbito. A anÃlise estatÃstica foi feita pelo programa SPSS versÃo 10.0. Resultados. Foram incluÃdos 287 pacientes, com mÃdia de idade de 36,8Â15,6 anos, sendo 80,8% do sexo masculino. Os principais sinais e sintomas apresentados foram febre (96,2%), mialgia (90,6%), icterÃcia (85,7%), cefaleia (74,2%), vÃmitos (70,7%), desidrataÃÃo (54%) e calafrios (53,7%). LRA foi observada em 237 pacientes (82%) pelo critÃrio RIFLE e 242 (84%) pelo AKIN. A mortalidade geral foi de 13%. A mortalidade foi semelhante nos pacientes que usaram e que nÃo usaram penicilina (11,6% vs. 13,7%, p=0,60). Aumento da mortalidade foi observado de acordo com as piores classificaÃÃes: RIFLE-R (2%), RIFLE-I (8%) e RIFLE-F (23%), assim como AKIN 1 (2%), AKIN 2 (8%) e AKIN 3 (23%), p < 0,0001. Os pacientes com oligÃria tiveram maior mortalidade (20%), em comparaÃÃo com os pacientes sem oligÃria (5%), p=0,02. Os fatores de risco independentes para Ãbito foram: RIFLE-F (OR=10,5, IC 95%=1,3-80,8, p<0,001), AKIN 3 (OR=7,5, IC 95%=2,2-25,2 p<0,001) e necessidade de diÃlise (OR=3,5, IC 95%=1,1-11,01, p=0,01). ConclusÃes. A LRA à uma complicaÃÃo frequente na leptospirose, com mortalidade significativa. Houve associaÃÃo entre as classificaÃÃes RIFLE e AKIN com a mortalidade na leptospirose. Os fatores de risco independentes para Ãbito sÃo classificaÃÃo RIFLE-F, AKIN 3 e necessidade de diÃlise. / Introduction. Leptospirosis is en endemic disease in Northeast of Brazil, which is characterized by potential fatal complications such as acute kidney injury (AKI). The aim of this study was to evaluate the clinical manifestations, the AKI classification and the risk factors for death in patients with the severe form of leptospirosis. Methods. A retrospective study was conducted in patients with severe form of leptospirosis admitted to tertiary hospitals in Fortaleza city, Northeast of Brazil. The clinical manifestations, laboratory tests at admission and during hospital stay, as well as treatment, were evaluated. AKI was defined according to the RIFLE and AKIN classifications, and the patients in each category were compared. Patients who used and who did not use penicillin, as well as survivors and non-survivors, were compared. Univariate and multivariate analysis were performed to investigate the risk factors for death. Statistical analysis was done with SPSS program version 10.0. Results. A total of 287 patients were included, with a mean age of 36.8Â15.6 years, and 80.8% were male. The main signs and symptoms at admission were fever (96.2%), myalgia (90.6%), jaundice (85.7%), headache (74.2%), vomiting (70.7%), dehydration (54%) and chills (53.7%). AKI was observed in 237 patients (82%) according to the RIFLE criteria and 242 (84%) according to AKIN. General mortality was 13%. Mortality was similar in patients who used and who did not use penicillin (11.6% vs. 13.7%, p=0.60). An increase in mortality was observed according to the worst classifications of RIFLE and AKIN: RIFLE-R (2%), RIFLE-I (8%) e RIFLE-F (23%), AKIN 1 (2%), AKIN 2 (8%) e AKIN 3 (23%), p<0.0001. Patients with oliguria had a higher mortality (20%), when compared to those without oliguria (5%), p=0.02. Independent risk factors for death were: RIFLE-F (OR=10.5, 95% CI=1.3-80.8, p<0.001), AKIN 3 (OR=7.5, 95% CI=2.2-25.2 p<0.001) and need of dialysis (OR=3.5, 95% CI=1.1-11.01, p=0.01). Conclusions. AKI is a frequent complication in leptospirosis, with significant mortality. There was association between RIFLE and AKIN classifications with mortality. Independent risk factors for death were RIFLE-F, AKIN 3 and need of dialysis.