A 48-year-old woman presents with recurrent severe arrhythmias due to hyperkalemia. Laboratory findings: serum potassium 6.0 mmol/L, serum chloride 110 mmol/L, CO2CP 16 mmol/L, urine pH 5.5. After correcting acidosis, the fractional excretion of sodium bicarbonate is 3%, and endogenous creatinine clearance is 45 ml/min. The most likely diagnosis is: