Objective: Renal dysfunction commonly accompanies the course of cardiac disorders and strongly associates with increased morbidity and mortality. Elevated central venous pressure is related to worsening renal function in patients with heart failure. However, predictors of worsening renal function in mitral stenosis-whose pathophysiologic process is similar to heart failure with regard to right heart dysfunction-are unknown. This study aimed to evaluate whether clinical and echocardiographic parameters might predict worsening renal function in patients with mild-to-moderate mitral stenosis. Methods: The current study has a prospective cohort design. Sixty consecutive patients (9 male, 51 female, mean age 50±13 years) with mild-to-moderate mitral stenosis were followed up for 34±13 months (range 1-60) and their renal functions were monitored. Worsening renal function was defined as a decline in glomerular filtration rate of ≥ 20% on follow-up. In order to presence or absence of worsening renal functions, study patients divided into two groups. Statistical analysis was performed using the Chi-square, Independent samples t / Mann-Whitney U tests, univariate and multivariate Cox proportional hazards analyses, receiver operating characteristic (ROC) and Kaplan-Meier curve analyses. Results: Worsening renal function was observed in 14 patients (23%). In univariate analysis, male gender, mean pulmonary artery pressure (mPAP), peak tricuspid regurgitation velocity, systolic pulmonary artery pressure, digitalis and antiplatelet usage, right atrial size, and TEI index were determined to be predictors of worsening renal function. In a multivariate Cox proportional hazards model, mPAP (HR=1.136, 95% CI: 1.058-1.220, p<0.001) and male gender (HR=4.110, 95% CI: 1.812-9.322, p=0.001) were associated with increased risk of worsening renal function during the follow-up period. In ROC curve analysis, the optimal cut-off value of mPAP to predict worsening renal function was measured as more than 21 mmHg, with 78.6% sensitivity and 58.7% specificity (AUC 0.725, 95% CI 0.595-0.838). According to the Kaplan-Meier curve, a significant difference was found between those who had mPAP of >21 mmHg, and those who did not have, in terms of worsening renal function (p=0.006), and the difference between the groups increased after 30 months of follow-up. Conclusion: Elevated mean pulmonary artery pressure at the time of initial evaluation, in patients with mild-to-moderate mitral stenosis, might help to predict worsening renal function.