Confirmation of complete mesocolic excision with central vascular ligation

The optimal extent of mesenteric dissection for cancer in the ascending colon is a subject of disagreement. Total mesorectal excision for rectal cancer has been shown to drastically decrease the likelihood of local recurrence and has been accepted as the gold standard of surgical resection, but complete mesocolic excision (CME) with central vascular ligation (CVL) for colon cancer has not been universally adopted.

CME removes the visceral fascia along the embryonic plane to separate the colon together with the undamaged, glistening mesocolic envelope from the parietal plane [1, 2]. CVL transects the supplying arteries and draining veins at their origin from the superior mesenteric vessels [1].

The evidence for an association between CME and longer overall or disease-specific survival has been mixed[3, 4]. Those who are skeptical of CME point out that the higher rates of complications (bleeding, respiratory impairment, and even death) associated with CME cannot be justified without clear evidence of better oncological outcomes[3, 5].

Proponents believe CME in combination with CVL to be oncologically superior to other surgical treatments of cancer in the ascending colon. Dissection along the embryonic planes avoids violation of the mesentery and the associated potential for tumor spread, and CVL allows for maximal removal of potentially involved mesenteric lymph nodes[6]. Higher lymph node harvest has been associated with longer survival[7], and the number of involved lymph nodes is the primary determinant of survival for patients with nonmetastatic colon cancer.

Published studies on CME-CVL are difficult to evaluate and compare because of inconsistent definitions, unclear description of the extent of dissection, and absence of randomization [8]. Often, the radicality of resection is self-reported by the surgeons. Additionally, the landmark papers by Hohenberger et al. and West et al. that provided much of the initial support of CME are beleaguered with methodological problems [9]. Verification of correct CME plane is insufficient without verification of the radicality of transection of the supplying vasculature. To facilitate reproducible verification of CVL, a multidisciplinary approach involving surgeons and pathologists is needed. We propose the following two-part method.

First, the surgical specimen should have a bridge of fatty lymphatic tissue medial to the bare area of the mesentery that connects the base of the vascular pedicles of the ileocolic vessels to the base of the right branches of the middle colic vessels (Fig. 1). This bridge incorporates the central lymph nodes of the Japanese D3 dissection [10]. Second, an intraoperative image should be taken of the proximal edge of the ligated pedicles at their takeoff from superior mesenteric vessels (Fig. 2).

Fig. 1.

Right hemicolectomy with CME-CVL shown anteriorly (A) and posteriorly (B). For verification of CVL, a bridge of tissue medial to the bare area that connects the vascular pedicles supplying the right colon needs to be seen on the gross specimen. This bridge incorporates the central nodes of a D3 dissection. 1, ascending colon; 2, transverse colon; 3, ileocolic vascular pedicle; 4, right colic vascular pedicle; 5, right branch of the middle colic vascular pedicle; 6, bare area of the mesocolon.

Fig. 2.

Intraoperative image of right-colon-supplying vascular pedicles ligated at their origin from the superior mesenteric vessels. SMV, superior mesenteric vein; SMA, superior mesenteric artery.

This two part confirmation of CVL radicality should be added to the already established pathologic grading of CME plane resection [2]. We strongly believe that pathologic confirmation of CVL will greatly facilitate standardization in efforts to definitively assess the efficacy of CME. We encourage pathologists to become familiar with the method of verifying CVL and to begin including CVL assessments in their reports on CME-CVL surgical specimens. Likewise, we encourage surgeons to take intraoperative images of the ligated named vessels in relation to the superior mesenteric vessels. The effectiveness of our proposed two-part verification method will need to be tested in a prospective clinical trial.