Development and growth of fasciae in and around the esophageal hiatus: a histological study using human fetuses.

Purpose: An entire fascial configuration at the esophageal hiatus might not be demonstrated histologically. According to observations of human fetus histology, the aim of this study was to consider which factor is likely to make the individual variation in adults.

Methods: We observed frontal histological sections containing the esophageal hiatus from 12 midterm fetuses at 12-16 weeks (crown-rump length: CRL, 85-137 mm) and 10 near-term fetuses at 26-30 weeks (CRL, 214-250 mm).

Results: At midterm, the transversalis fascia covering the diaphragm turned upward to join the adventitia of the left aspect of the esophagus: thus, the upper leaflet of the phreno-esophageal membrane was established first. A connection between the adventitia and endothoracic fascia (i.e., the upper leaflet of the PEM) was deleyed in the right. At near-term, both the transversalis and endothoracic fasciae often joined the adventitia in the left side but not in the right side. Therefore, fascial development advanced in the left side as well as the inferior side of the hiatus. The foregut-midgut junction, suggested with cytokeratin 5/6 immunostaining, was located in the hiatus.

Conclusion: Development and growth of the phreno-esophageal membrane showed left/right and superior/inferior differences. The transiently-appeared pleural recess, the upward protruding right crus of diaphragm and, the right liver and adrenal extending upward seemed to disturb the fascial connection to the adventitia in the right and/or superior side. Individual variations in the fascial configuration at the hiatus might occur due to the site-dependent delay of the establishment of structures.