Vessels and Structures Ligated and Removed in Left Hemicolectomy and Extended Left Hemicolectomy
Left Hemicolectomy
In a standard left hemicolectomy, the inferior mesenteric artery (IMA) is ligated at its origin from the aorta (high ligation), and the inferior mesenteric vein (IMV) is ligated at the level of the duodenojejunal ligament, with removal of the descending colon and its mesentery including regional lymph nodes. 1, 2
Vascular Structures Ligated:
- Inferior mesenteric artery (IMA) - ligated flush to the aorta for oncologic resections 3
- Inferior mesenteric vein (IMV) - ligated at the level of the duodenojejunal ligament 4
- Left colic artery (LCA) - removed with the specimen as it branches from the IMA 5
- Sigmoid arteries - may be preserved or ligated depending on the extent of sigmoid colon preservation 5
Anatomic Structures Removed:
- Descending colon - from the splenic flexure to the sigmoid colon 1, 2
- Mesocolon - complete mesocolic excision (CME) to the level of the duodenojejunal ligament 4
- Regional lymph nodes - minimum of 12 lymph nodes must be resected for adequate staging 1, 2
- Segment of colon - at least 5 cm on either side of the tumor, though wider margins are typically included due to obligatory arterial ligation 1, 2
Important Caveat:
In benign disease (diverticulitis or polyposis), the IMA may be cut just below the branch of the left colic artery rather than at its origin, preserving more blood supply to the sigmoid colon 3
Extended Left Hemicolectomy
Extended left hemicolectomy requires additional ligation of vessels supplying the distal transverse colon and splenic flexure, potentially including the left branch of the middle colic artery or accessory middle colic artery, with removal extending from the mid-transverse colon to the sigmoid colon. 4, 5
Additional Vascular Structures Ligated (Beyond Standard Left Hemicolectomy):
- Left branch of the middle colic artery (MCA) - frequently ligated in extended resections 6
- Accessory middle colic artery (A-MCA) - when present, may be ligated depending on tumor location 5
- Accompanying vessels branching from the A-MCA - ligated when they supply the tumor-bearing segment 5
Additional Anatomic Structures Removed:
- Distal transverse colon - extending from the mid-transverse colon 4, 6
- Splenic flexure - complete mobilization and removal 4, 7
- Extended mesocolon - with complete mesocolic excision to the splenic flexure area 4
Critical Technical Considerations:
The middle colic artery is ligated in approximately 82.7% of extended left hemicolectomies when right colonic transposition is required for tension-free anastomosis 6. However, when a modified Deloyers procedure is performed, the middle colic vessels can be preserved while still achieving adequate reach for anastomosis 4.
Reconstruction Challenges:
When the residual transverse colon is too short to reach the pelvis after extended left hemicolectomy, two options exist:
- Right colonic transposition (RCT) - requires middle colic artery ligation in most cases 6
- Complete intestinal derotation (CID) - preserves the middle colic artery in 50% of cases 6
Both techniques have similar anastomotic complication rates (6.9% vs 20%, not statistically significant), though RCT more frequently requires additional colonic resection 6.
Oncologic Principles:
The extent of colonic resection is determined by blood supply distribution and regional lymph node drainage, with the goal of wide resection of the involved bowel segment together with removal of its lymphatic drainage 1, 2. Complete mesocolic excision with high vascular ligation ensures adequate lymph node harvest and reduces the risk of understaging 2.