Objectives: This study aimed to estimate the safety and efficacy of endoscopic ultrasound-guided choledochoduodenostomy (EUS-CDS) and endoscopic ultrasound-guided hepaticogastrostomy (EUS-HGS) for malignant biliary obstruction. Methods: We conducted a literature search using PubMed, Embase, Web of Science, the Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov. Studies that compared EUS-CDS and EUS-HGS were included in this study. Results: Thirteen studies were eligible for inclusion. The technical [odds ratio (OR): 0.95; 95% confidence interval (CI): 0.51-1.74) and clinical (OR: 1.13; 95%CI: 0.66-1.94) success rates of EUS-CDS were comparable to those of EUS-HGS. However, EUS-CDS had less reintervention (OR: 0.31; 95%CI: 0.16-0.63) and stent obstruction (OR: 0.48; 95%CI: 0.21-0.94) than EUS-HGS. Both groups had similar adverse events (OR: 1.00; 95%CI: 0.70-1.43) and overall survival (hazard ratio: 1.07; 95%CI: 0.58-1.97). Conclusions: EUS-CDS and EUS-HGS have comparable technical and clinical success rates, adverse events, and overall survival. However, EUS-CDS has less reintervention and stent obstruction.

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Existing optical theory states that the light directed to the optical center of the convex lens will travel in a straight line. Does the theory hold? If this is true, then why the images formed by the camera lens tends to be distorted? To answer the question, this paper studied the propagation mode of light passing through convex lens. Specifically, assuming the propagation medium on both sides of convex lens is homogeneous, we propose an angular affine transformation (AAT) theory. Based on the proposed theory, we first derive the refractive index of convex lens as well as the method of calculating the normal direction of each point within the radius of convex lens radius and then derive the refraction direction of each point within the radius of convex lens, thus completely characterizing the path diagram of light directed to the optical center. The correctness of the proposed theory has been verified using two sets of experiments: characterization of the route of light passing through the convex lens as well as camera imaging experiment. From the results, it can be concluded that the light directed to the optical center of convex lens does not travel in a straight line, but in a refraction line.