This study evaluates distal tubular damage in early stages of renal disease in dogs with naturally acquired leishmaniosis. Pherograms of urinary proteins separated in vertical electrophoresis system (SDS-PAGE) were evaluated. Peptide fingerprint and fragmentation (MALDI-TOF TOF) identified bands located at 100 and 60 kDa as Tamm-Horsfall protein (THP) and albumin, respectively. The variables examined were: urine protein to creatinine ratio (UPC), total number of bands, quantification of THP urinary excretion through the optical density (OD %) of bands located at 100 kDa, blood creatinine, and urine specific gravity (USG). Positive correlation was found between UPC and the number of bands (ρ = 0.75849, P = <0.0001). Negative correlation was identified between UPC and OD % of 100 kDa bands (ρ = -0.85332, P = <0.0001), and the number of bands and OD % of 100 kDa bands (ρ = -0.74479, P = <0.0001). The area under the ROC curve was 0.991 (95 % CI, 0.976-1). The optimal cut-off UPC that better discriminated between urines with high or low OD% of THP was 0.46 with 92.6 % sensitivity and 96.2 % specificity. Our findings indicate that non azotemic dogs with borderline proteinuria might excrete low amount of THP, which could suggest tubular damage in early stages of chronic kidney disease.