BackgroundEndoscopic bilateral biliary drainage is a first line palliative treatment for unresectable MHBO but remains technically challenging. The emergence of news SEMS carried by an ultra-thin (6Fr or smaller) delivery system now permits simultaneous bilateral stent placement. To date, only few data comparing this new method to conventional sequential bilateral stenting are reported. We conducted a monocentric retrospective study to evaluate a possible superiority of simultaneous “side by side” (SBS) biliary drainage.MethodsWe identified 135 patients who benefited from bilateral drainage using uncovered SEMS between 2010 and 2023. Among them, 62 benefited from simultaneous SBS bilateral drainage between 2017 and 2023, and 73 benefited from sequential bilateral drainage (38 using “stent in stent” (SIS) technique and 35 using SBS technique, between 2010 and 2017).ResultsTechnical success was significantly more observed in simultaneous drainage compared to sequential drainage (94% vs 75%, p=0.008). However, simultaneous SBS drainage and sequential SIS drainage had a similar technical success (94% vs 95%). We observed no differences regarding clinical success, procedure duration and RBO rate. Stent patency was shorter in SIS group compared with simultaneous group (103 vs 144 days). Early adverse events (AE) were more frequent in sequential group (31% vs 21%, p=0.205), with no differences regarding SIS or SBS technique. Technical failure was associated with a higher rate of infectious fatal AE (9.5% vs 1.7%, p=0.02). Reintervention after RBO seems to be more successful after using SBS rather than SIS techniques (83% vs 75%, p=0.53).ConclusionSimultaneous side by side endoscopic bilateral metallic stent placement using an ultra-thin delivery system is technically easier and as efficient as sequential bilateral stenting in unresectable MHBO to achieve bilateral drainage. Stent in stent procedure remains a good option in unresectable MHBO. Further prospective multicentric trials are needed to investigate the place of simultaneous SBS technique as a first-line treatment compared to SIS technique.