The aim of this study was to evaluate the histopathological changes in the urinary system and their correlation with serum biochemical parameters, parasite load and immunodetection of amastigotes in 30 dogs infected naturally by Leishmania infantum. The major histological changes were glomerulonephritis and interstitial nephritis. Serum biochemistry demonstrated that the dogs had progressive loss of renal function. L. infantum amastigotes were detected immunohistochemically in all parts of the urinary system, except the ureters. There was a correlation between parasite load, severity of histopathological changes and immunodetection of the parasites, but parasite load was not correlated with the serum biochemical parameters evaluated.