Malignant ureteral obstruction often necessitates chronic urinary diversion and is associated with high rates of failure with traditional double-J ureteral stents. To overcome drawbacks of the double-J stent, recently, metallic stents have been used to manage for palliative treatment in patients with ureteral obstruction associated with end stage malignant disease. The success rates of metallic stents have been reported to be high and the method proved to be useful in patients with malignant ureteral obstruction. In addition, covered metallic stents have many advantages compared with bare metallic stents, such as lower rate of tissue invasion and higher patency rate. However, there is little investigation about comparison of clinical efficacy between covered-metallic stents and double-J stents in malignant ureteral obstruction.

Therefore, investigators plan to perform a prospective randomized study to compare clinical efficacy of silicone-covered metallic ureteral stent and double-J ureteral stent in patients with malignant ureteral obstruction.

Inclusion Criteria:

1. Age 20-80 years
2. Malignant mid- to distal ureteral obstruction by abdominal or pelvic malignancy with overt hydronephrosis documented on CT scans
3. Expected life expectancy more than three months

Exclusion Criteria:

1. History of unilateral nephrectomy or bladder reconstruction
2. History of kidney transplantation
3. History of severe allergy to contrast media
4. State of dialysis
5. Performance status - 3 or 4 on ECOG scale