Revisiting the infracardiac bursa using multimodal methods: topographic anatomy for surgery of the esophagogastric junction

In embryology, the infracardiac bursa (ICB) is a well-known derivative separated from the omental bursa. During surgeries around the esophagogastric junction (EGJ), surgeons often encounter a closed space considered to be equivalent to the ICB, but the macroscopic anatomy in adults is hardly known. This study aimed to revisit the ICB using multimodal methods to show its development from the embryonic to adult stage and clarify its persistence and topographic anatomy. Histological sections of 79 embryos from Carnegie stage (CS) 16 to 23 and magnetic resonance (MR) images of 39 fetuses were examined to study the embryological development of the ICB. Horizontal sections around the EGJ obtained from three adult cadavers were examined to determine the topographic anatomy and histology of the ICB. Further, 32 laparoscopic surgical videos before (n = 16) and after (n = 16) the start of this study were reviewed to confirm its remaining rate and topographic anatomy in surgery. The ICB was formed in 1 out of 10 CS17 samples, and in 8 out of 10 CS18 samples. Further, it was observed in all CS19-23 except one CS23 sample and in 25 (64%) out of 39 fetus samples. Three-dimensional reconstructed MR images of fetuses revealed that the ICB was located at the right alongside the esophagus and the cranial side of the diaphragmatic crus. In one adult cadaver, the caudal end of the ICB arose from the level of the esophageal hiatus and the cranial end reached up to the level of the pericardium. The inner surface cells of the space consisted of the mesothelium. In laparoscopic surgery, the ICB was identified in only 11 (69%) out of 16 surgeries before. However, subsequently we were able to identify the ICB reproducibly in 15 (94%) out of 16 surgeries. Thus, the ICB is the structure commonly remaining in almost all adults as a closed space located at the right alongside the esophagus and the cranial side of the diaphragmatic crus. It may be available as a useful landmark in surgery of the EGJ.