De Ledinghen 2000.

Methods	Generation of the allocation sequence: method unclear. Allocation concealment: consecutively numbered series of sealed envelopes. Blinding: not blinded. Intention‐to‐treat: yes. Exclusions from analysis: no. Follow up period: 240 days. Jadad‐score: 3.
Participants	Sixty‐two patients with malignant biliary stricture and endoscopically inserted biliary polyethylene stent.
Interventions	Ursodeoxycholic acid (13‐15 mg/kg/d) and norfloxacin (400 mg/d) versus no treatment.
Outcomes	Duration of stent patency. Mortality.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Unclear risk	B ‐ Unclear