Submucosal injection is currently used in GI endoscopy to reduce resection risks and to perform submucosal dissection; it is usually performed via an injection needle or a needleless device. The aim of the study was to compare 2 submucosal injection modalities (needle-assisted vs needleless) by using substances with different viscosities.

Needle and needleless injections were compared by assessing the efficacy of tissue elevation with 5 different substances in an ex vivo porcine model. The height of the submucosal elevation was measured 0(t0), 10(t1), and 30 minutes after injection (t2). Viscosity of the solution was also measured.

For both stomach and rectum, at t0, t1, and t2 no difference in the height of the elevation was found between the needle and needleless technique, irrespective of the substance. Tissue elevation in the stomach was similar between the 2 techniques at t0 (9.9 ± 1.58 vs 9.4 ± 1.3 mm, P = .3), t1 (7.2 ± 1.56 vs 6.9 ± 1.4 mm, P =. 26), and t2 (6 ± 1.6 vs 5.5 ± 1.3 mm, P = .18). No difference was found in the rectum at t1 and t2, whereas a slightly higher elevation with the needle-assisted technique was observed at t0 (t0: 12.4 ± 1.3 vs 11.2 ± 1.6 mm, P = .003; t1: 8.7 ± 1.3 vs 8.3 ± 1.5 mm; P = .32; t2: 7.0 ± 1.4 vs 7.2 ± .76 mm; P = .75). When comparing the substances with normal saline solution, more viscous solutions showed a significantly higher elevation at t0, t1, and t2 irrespective of the injection modalities and the location.

No differences were found in the height of submucosal injection or in the persistence of such elevation when comparing needleless with needle-assisted injection, with the only minor exception of the initial elevation in the rectum, which does not appear to be clinically relevant. Viscous solutions resulted in higher and more persistent elevations as compared with normal saline solution.