Resection in Neoplastic Conditions

Adenomatous polyps: as discussed above, the majority of adenomatous lesions can be removed by endoscopic techniques. However, large sessile polyps > 5 cm in diameter and occupying more than one third of the colon circumference should be removed by a localised resection. Sessile adenomas in the rectum can be removed by transanal submucosal resection. In this procedure adrenaline solution is infiltrated into the submucosa around the lesion and the mucosa is incised

Table 5.1. Colorectal resections

Specific

diverticular disease

volvulus

pneumatosis coli

colonic angiodysplasia

rectal stump (CIBD, diversion proctitis)

rectal mucosa (prolapse)

Ulceroinflammatory

ulcerative colitis

Crohn's disease

pseudomembranous colitis

ischaemia

Neoplasia

large or multiple adenomas

carcinoma

malignant lymphoma

Right Colectomy
Figure 5.5. Types of colonic resection. From Rob and Smith's operative surgery of the colon, rectum and anus, 5th edition. Fielding LP, Goldberg SM (Eds), 1993. Reprinted with permission of Elsevier Science.

A ^ C: ±A + B ^ D: ±A + B ^ F: ±A + B ^ G: ±E + F ^ G ± H: G ^ I: F ^ I J + K

Ileocaecectomy Ascending colectomy Right hemicolectomy Extended right hemicolectomy Transverse colectomy Left hemicolectomy Extended left hemicolectomy Sigmoid colectomy Subtotal colectomy Total colectomy Total proctocolectomy Proctectomy by scissors 1 cm from the lesion. This can then be easily lifted off the circular muscle in a single piece and the mucosal defect is closed by sutures. Occasionally, large rectal polyps may require formal proctectomy or anterior resection.

Malignant lesions: the type of resection for colonic tumours will depend on the site of the lesion and the intent of the surgery. As previously stated, the colonic lymphatics accompany the main blood vessels and the extent of resection depends on the lymphatic clearance required. In cancer operations of curative intent the affected colon with its lymphovascular mesenteric pedicle is resected. Continuity is restored by either an ileocolic or colocolic end-to-end anastomosis.

However, on occasion an end ileostomy/colostomy may be required if the surgeon thinks that primary anastomosis would be compromised (e.g., if there is extensive intraperitoneal contamination).

The curative resection of rectal tumours may be carried out by one of two methods:

• Anterior resection of rectum - in this procedure the rectum is mobilised by entering the fascial plane around the mesorectum. This allows the rectum to be removed en bloc with the mesorectum which contains the initial draining lymphovascular channels and nodes (low anterior resection and total mesorectal excision - TME) (Figure 5.6a). Continuity is re-established by a stapling device forming an end-to-end colorectal anastomosis. Occasionally, in low anastomoses, a protective loop colostomy/ileostomy may be fashioned to divert the faecal stream. This can be closed at a later date. To obtain an adequate length of colon to form a safe anastomosis the splenic flexure will usually need to be mobilised. On occasions the spleen may be damaged during this mobilisation and a splenectomy would then have to be performed. In cases where the tumour is in the proximal rectum, a high anterior resection and mesorectal division can be employed. This entails division of the rectum and mesorectum 5 cm distal to the tumour and allows a larger rectal stump for anastomosis.

• Abdominoperineal (AP) resection of rectum - in this procedure the rectum is mobilised as above and the colon is divided at the apex of the sigmoid. The anal canal and distal rectum are then resected from below via the perineal route (Figure 5.6b). The entire rectum (and mesorectum) and anus are then removed en bloc. The perineal wound is closed and a permanent end colostomy is fashioned in the left iliac fossa using the transected end of the sigmoid colon.

Until the early 1980s anterior resection was used in less than 50% of patients with rectal tumours, i.e., those in the proximal rectum. However, it is now used for approximately 90% of tumours in the rectum. Initially it was feared that, because less tissue is excised and the clearance of the distal margin is not as great during anterior resection, there would be increased local recurrence rates if anterior resection was used for low rectal tumours. However, it appears that the degree of lateral clearance is similar in the two procedures and that a distal clearance of 2 cm is adequate to prevent local recurrence. Given the physical and psychological problems associated with a permanent colostomy, and the higher incidence of bladder and sexual problems in patients undergoing AP resection, it is felt that a sphincter-saving procedure (i.e., anterior resection) should be employed whenever possible. However, tumours extending to less than 2 cm from the anorectal junction (i.e., less than 6 cm from the anal verge) should be treated by AP resection.

Occasionally, in a medically unfit patient, localised resection is used for a well-differentiated, pT1 rectal cancer that is <3 cm diameter. Accurate preoperative staging is crucial in selection of these patients and some may then need to proceed to salvage resection if adverse pathological features are identified in the pathological specimen, e.g., poor differentiation, lymphovascular involvement or invasion of muscle coat. Sometimes patients with obstructing cancers undergo partial laser ablation or stenting to restore intestinal continuity and avoid the risk of perforation. This may even allow resection to be carried out more safely at a later date.

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