Anatomical observation of the right retroperitoneal fascia and its clinical significance in complete mesocolic excision for right colon cancer

Objective: To investigate the anatomic characteristics of the right retroperitoneal fascia and its surgical implementation while performing complete mesocolic excision (CME) for right colon cancer. Methods: A descriptive study was carried out. (1) Clinicopathological data and surgical videos of 17 non-consecutive patients undergoing laparoscopic right hemicolectomy (extended right hemicolectomy) with CME for right colon cancer at Department of Colorectal Surgery of Union Hospital, Fujian Medical University between January 2020 and October 2020 were retrospectively collected. The construction of right retroperitoneal fascia was observed from caudal dorsal direction and caudal ventral direction. (2) Three postoperative specimens from 3 cases undergoing laparoscopic right hemicolectomy with CME for right colon cancer in June 2020 were prospectively included to observe anatomy and examine histology. (3) Five abdominal cadaver specimens from the Department of Anatomy of Fujian Medical University were enrolled, including 3 males and 2 females. Anatomical observation and histological studies were performed from the cranial approach and the caudal dorsal approach. Masson staining was used to examine the histology. Results: (1) Surgical video observation: The typical structure of right retroperitoneal fascia could be observed in all the 17 patients. The fascia was a rigid barrier between the posterior space of the ascending colon and the anterior pancreaticoduodenal space behind the transverse colon. The right retroperitoneal fascia should be sharply cut to communicate between the two spaces to avoid entering the right mesocolon by mistake. The severed ventral stump of the right retroperitoneal fascia ran along the dorsal side of the right hemicolon to the lateral side, and the dorsal stump covered the level of the duodenum caudally, and continued to move downward, covering the surface of Gerota's fascia. (2) Observation of 3 surgical specimens: The dorsal side of the right mesocolon was smooth and intact, which could be anchored in the corresponding area of the lateral edge of the duodenum. The ventral stump of the right retroperitoneal fascia could be seen, which attached to the dorsal side of the right mesocolon semi-circularly. Masson staining observation: The ventral stump of the right retroperitoneal fascia ran cephalad, fused with the dorsal side of the right mesocolon tightly and curled. The caudal side of confluence and the dorsal side of the right mesocolon presented a bilobed structure. (3) Anatomy of 5 cadaveric specimens: The right retroperitoneal fascia was a thin fascia structure, which was a rigid barrier between the anterior pancreaticoduodenal space behind the transverse colon and the posterior space of the ascending colon. The ventral stump of the right retroperitoneal fascia (including the dorsal side of the right mesocolon), the dorsal stump of the right retroperitoneal fascia (including part of the duodenal wall) and the dorsal side of the right mesocolon were retrieved for histological examination. The ventral stump of the right retroperitoneal fascia fused with the dorsal side of the right mesocolon by the cephalic side, and the dorsal side of the right hemi-mesocolon on the fusion level by caudal side gradually separated into a double-layer loose fascial structure. The dorsal stump of the right retroperitoneal fascia covered the surface of the duodenum level, moved on from the ventral side to the surface of the prerenal fascia, and continued to the caudal side. Conclusions: The right retroperitoneal fascia is a rigid barrier between the anterior pancreaticoduodenal space behind the transverse colon and the posterior space of the ascending colon. The Toldt fascia formed by fusion with the dorsal lobe of the right colon travels to the edge of the descending and horizontal part of the duodenum and separates again. The right retroperitoneal fascia is attached to the edge of the duodenum, reversing and running on the surface of the prerenal fascia, while the dorsal lobe of the right colon runs in front of the pancreas and duodenum, and shifts to the pancreaticoduodenal fascia. During the operation, this fascia should be identified and cut to penetrate the anterior pancreaticoduodenal space behind the transverse colon and the posterior ascending colon space, which helps to ensure the integrity of the dorsal side of the right hemi-mesocolon.