Concentrating ability of the kidneys in proteinuric patients

Proteinuria causes damage to renal tubulointerstitum. The study included 50 patients (24 males and 26 females), mean age 46.50 +/- 13.08 years, with average endogenous creatinine clearance 87.29 +/- 31.17 ml/min. Regarding level of glomerular proteinuria patients were divided into three groups. The first group, with proteinuria less than 0.3 g/24 h, included 19 patients (7 male and 12 female), average age 45.12 +/- 13.28 years and mean clearance of endogenous creatinine 94.27 +/- 34.70 ml/min. The second group, with proteinuria between 0.3 and 3.0 g/24 h, comprised 18 patients (8 male and 10 female), mean age 45.39 +/- 12.64 years, and with mean clearance of endogenous creatinine 90.07 +/- 31.89 ml/min. The third group consisted of 13 patients (9 male and 4 female) with proteinuria values higher than 3.0 g/24 h, average age 50.08 +/- 13.73 years and mean endogenous creatinine clearance 73.25 +/- 20.44 ml/min. In order to assess the concentrating ability of the kidneys we investigated: urine osmolality, osmolar concentration index, fractional osmolar excretion, fractional urea excretion and free water clearance. Results were statistically analyzed using Student t test, Mann-Whitney U test and chi 2 test. Proteinuria leads to deterioration of concentrating ability of the kidneys.