Using the Drug Spironolactone to Test If It Reduces Protein Leakage From the Kidney

Inclusion Criteria: * Proteinuria more than 1.5 g/day * On ACEI for more than 6 months * Serum creatinine less than 200 micromol/L with less than 20% variability in the preceeding 3 months * Creatinine clearance more than 30 ml/min, with less than 20% variability in the preceeding 3 months Exclusion Criteria: * Serum potassium level more than 5 mmol/L * Treatment with corticosteroids, NSAID or immunosuppressant medication * Acute myocardial infarction or cerebrovascular accident in the previous 6 months * Severe uncontrolled hypertension (diastolic \> 115 mmHg or systolic BP \[blood pressure\] \> 220 mmHg) * Evidence or suspicion of renovascular disease, obstructive uropathy, collagen disease, cancer, drug or alcohol abuse, pregnancy, or breast feeding and ineffective contraception