Do polyglycolic acid sheets really prevent bleeding after endoscopic submucosal dissection? An opinion from physiological viewpoints
18 December 2019 (online)
We read with interest the publication by Kataoka et al.  and offer the following comments.
Bioresorbable polyglycolic acid (PGA) sheets are widely used in surgery and have recently been applied to ulcers resulting from endoscopic submucosal dissection (ESD). In vivo, PGA sheets undergo nonenzymatic hydrolysis with the resulting glycolic acid being completely metabolized in about 15 weeks. Animal and human studies have shown that PGA implantation provokes acute and prolonged inflammation by foreign-body reaction and localized acidification. In only a few hours, degraded PGA and glycolic acid induce acute inflammation, as demonstrated by neutrophil infiltration .
In the Kataoka study, the PGA shielding method could not demonstrate significant effects in preventing post-ESD bleeding . Interestingly, all three cases of post-ESD bleeding in the PGA group occurred within a week, whereas all four bleeding cases in the control group occurred after 8 days. Positive results reported by Tsuji et al.  and Kawata et al.  showed similar findings. In both studies, there were three cases of bleeding in the PGA group, two of which occurred within 4 days; bleeding in the control group was random. From these results and known facts of PGA implants, we suspect that an acute inflammatory response to this artificial material and the associated pH changes aggravate post-ESD bleeding in the early post-procedure phase, although we agree with the authors that their methods might be effective for preventing late-phase bleeding. Additionally, early bleeding PGA-shielded post-ESD ulcers possibly produce further endoscopic hemostasis difficulties because the degenerated PGA sheet obstructs accurate identification of the bleeding point. Thus, we suggest that PGA shielding might actually promote post-ESD bleeding, leading to the negative conclusion of this study. The endoscopy community might improve its understanding of clinically available biodegradable materials, including mechanisms of action and response in the human body.
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