🔪 Colonic Surgery
Which operation for which tumour location — resection extents, vascular ligation targets, surgical planes, anastomotic options, and the rationale behind each oncological procedure.
The Oncological Principle of Colonic Resection
All colonic resections for cancer follow the same fundamental principle: remove the primary tumour together with its entire lymphovascular drainage territory. The lymph nodes that drain a colonic segment travel alongside its named blood vessels — so the operation is defined by which vessel is ligated at its origin.
Why “High Tie” — The Vessel Ligation Principle
For colonic cancer surgery, each named artery is ligated at its origin from the superior or inferior mesenteric artery (a “high tie”). This achieves two things simultaneously:
🔵 Maximal lymph node harvest — the lymphatic chain travels alongside the artery from the bowel wall to the origin. Ligating at the origin includes ALL nodes along that chain (epicolic → paracolic → intermediate → principal nodes).
🔵 Adequate margins — 5 cm proximal and distal clear margin from the tumour as a minimum; in practice the resection is defined by the vascular territory, not measured from the tumour edge.
The number of lymph nodes retrieved (minimum 12 nodes for adequate staging by NICE/RCS guidelines) determines whether N staging is accurate. Fewer than 12 nodes = inadequate resection for staging purposes.
CME is the colonic equivalent of Total Mesorectal Excision (TME). The principle:
- Dissect in the embryological fascial plane between the mesocolon (visceral fascia) and the retroperitoneum (parietal fascia) — the “holy plane” for the colon
- Keep the mesocolon intact as an envelope — no breaches, no “coning” toward the tumour
- Ligate the feeding vessel at its origin (central vascular ligation — CVL)
- Evidence: CME + CVL reduces local recurrence from ~7% to ~3% and improves 5-year survival by ~15% compared to standard colectomy (Hohenberger data, Erlangen)
| Tumour Location | Operation | Vessel(s) Ligated at Origin | Anastomosis |
|---|---|---|---|
| Caecum, appendix, proximal ascending colon | Right hemicolectomy | Ileocolic artery ± right colic artery (at SMA origin) | Ileocolic (ileum to transverse colon) |
| Mid-ascending colon, hepatic flexure | Extended right hemicolectomy | Ileocolic + right colic + middle colic arteries (all at SMA origin) | Ileocolic (ileum to mid-transverse / descending colon) |
| Transverse colon | Extended right hemicolectomy (most common) or transverse colectomy | Middle colic artery at SMA origin | Ileocolic or colocolonic |
| Splenic flexure | Extended right hemicolectomy OR left hemicolectomy (depends on position) | Middle colic ± left colic at IMA origin | Ileocolic or colocolonic |
| Descending colon | Left hemicolectomy | Left colic artery (at IMA origin) | Colocolonic (transverse to sigmoid) |
| Sigmoid colon | Sigmoid colectomy / High anterior resection | IMA at its aortic origin (high tie) or below the left colic take-off (low tie) | Colorectal (descending colon to upper rectum) |
| Upper rectum (above peritoneal reflection) | High anterior resection (HAR) | IMA at origin. Superior rectal artery divided. | Colorectal anastomosis above peritoneal reflection |
| Mid/lower rectum (at/below peritoneal reflection) | Low anterior resection (LAR) + TME | IMA at origin. Full TME to pelvic floor. | Colorectal / coloanal anastomosis ± defunctioning loop ileostomy |
| Low rectum (within 1–2 cm of anal sphincter) | Abdominoperineal resection (APR) | IMA at origin. Permanent end colostomy. | None — permanent colostomy |
For sigmoid and rectal cancer, there is a specific decision regarding where to ligate the IMA:
| Tie type | Where | Lymph nodes cleared | Risk | Current recommendation |
|---|---|---|---|---|
| High tie | At the IMA origin from the aorta — above the left colic artery take-off | All IMA territory nodes including apical/origin nodes | Left ureter at highest risk (must be identified). Sympathetic nerve injury (ejaculatory dysfunction in men). Left colon blood supply depends on middle colic collaterals via marginal artery. | Standard for rectal cancer. Better oncological clearance for apical nodes. |
| Low tie | Below the left colic artery origin — preserving the left colic artery | Sigmoid and superior rectal nodes only | Apical nodes not cleared. May leave tumour-positive nodes behind if N3 disease. | Occasionally used for sigmoid cancer where the left colic preservation improves descending colon perfusion for the anastomosis. Less common. |
The Left Ureter — The Single Most Important Structure in Left Colonic Surgery
The left ureter runs retroperitoneally, immediately posterior to the descending colon and sigmoid mesocolon. During high IMA ligation:
🔴 The ureter crosses posterior to the IMA root
🔴 The left gonadal vessels cross anterior to the ureter at the pelvic brim (“water under the bridge”)
🔴 The ureter must be positively identified and protected before the IMA is divided
Routine pre-operative ureteric stenting is used in: re-operative pelvic surgery, locally advanced tumours, post-radiation fields, or any case where the anatomy may be distorted.