Ohtaka M, et al. - Authors assessed the risk factors for predicting ureteral stent failure in patients with malignant ureteral obstruction (MUO) following ureteral stent insertion and the change in the renal function after retrograde ureteral stent insertion in cases of bilateral hydronephrosis. For predicting stent failure, age > 60 years was helpful. Stent failure could be predicted with MUO due to gastrointestinal cancer and bilateral hydronephrosis. By the help of these factors, urologists could decide the optimal time to perform early percutaneous nephrostomy. As per data, ureteral stent placed into both sides of the hydronephrosis was not necessary for the patients with bilateral hydronephrosis.