OBJECTIVE The aim of the study was to evaluate the renal resistive index (RI) and pulsatility index (PI) in patients with pleural effusion (PE). METHODS We studied the mean renal RI and PI in 50 patients with PE and 30 healthy volunteers by Doppler sonography. We grouped effusion as unilateral and bilateral. Statistical analysis was done by independent t test and correlation coefficient analysis. RESULTS The mean RI/PI in healthy volunteers and in PE patients was 0.58/0.93 and 0.72/1.35, respectively. We observed a significantly higher RI and PI in patients when compared with healthy volunteers (all p < 0.001). We found no difference between the renal RI or PI related to unilateral (0.71 or 1.34, respectively) or bilateral effusion (0.74 or 1.55, respectively) (p > 0.05). CONCLUSIONS Pleural effusion might result in increased renal impedance as seen in cirrhosis, which is a rather complicated pathophysiological process, without causing any morphological changes in kidneys.