Like cancers anywhere in the body, radical resection is the only curative treatment available for carcinoma of rectum. Such radical resection means excision of the rectum with its sheath along with all nodes lying on the wall with 5cm normal tissue above and below the growth and all involved regional lymph nodes.
Obviously if the main nodes are involved the only way to do radical surgery is to ligate inferior mesenteric artery at its origin from the aorta (flush ligation). But this requires excessive resection of the bowel. So the surgeon usually prefers to ligate inferior mesenteric artery below the origin of 1 or 2 branches.
Types Of Colorectal Resection
The type of resection which should be employed in a particular case depends on the situation of the carcinoma. For this, rectum has been divided into three parts-
- The proximal third extends from the junction with the sigmoid colon which is 15 or 16cm above the anus.
- The middle-third extends from 11cm down to the lowest portion of the anterior reflexion (pouch of Douglas) which is at 6 to 7cm in females and 7 to 8cm in males above the anus.
- The distal third of rectum includes the anal canal.
Proximal Rectal Carcinomas
Cancers with lower margin at or above 11cm can always be removed by low anterior resection and primary anastomosis conserving the sphincter mechanism.Temporary proximal de-functioning colostomy may be advisable to secure anastomosis. In young subjects in whom cancers grow rapidly, probably it will be better to do abdomino-perineal resection instead of anterior resection to avoid recurrence.
In these cases it is rather difficult to do anterior resection conserving sphincter mechanism as this is almost invariably followed by recurrence as if a typical 5cm normal rectum has to be removed distal to the growth there is hardly any space to do the anastomosis (joining).
In these cases-
- Abdomino-perineal resection will be safest.
- If the permanent colostomy has to be avoided one may perform abdomino-perineal pull through operation and making the anastomosis outside the anus to avoid the problem of doing an anastomosis deep in the pelvis. After the resection of the lesion by the abdominal approach, the proximal colon is drawn to the anorectal stump and is sutured outside the anal canal.
- There is now available stapling instrument, the E. E. A. stapler that creates an inverting end-to-end anastomosis. This has made it technically possible to resect mid-rectal carcinomas down to the distal limit and to restore continuity by a safe end-to-end anastomosis.
Distal Rectal Carcinomas: In these cases abdomino-perineal resection (Miles) or perineo-abdominal resection (Gabrial) is the method of choice.
This is an excellent operation in old and inept persons who may not stand an abdomino-perineal resection.
- Through an abdominal incision the rectum is excised like radical resection. The remnant of the rectum is closed by suturing and the peritoneum is over-sewn.
- The pelvic defect is covered in the usual way.
- As the cancers in these patients spread slowly this operation works well.