Sphincter-Preserving Surgery for Low Rectal Cancer

Sphincter-preserving surgery for low rectal cancer removes the tumour while keeping the anal sphincter muscles, so the patient continues to pass stool normally instead of living with a permanent stoma. Even for tumours lying very low in the rectum, intersphincteric resection, which dissects between the internal and external anal sphincters, makes this possible in most patients, provided the plane between those muscles is free of cancer.

The case for this operation was the centrepiece of the masterclass given by Dr. Kaushal Kishor Yadav, currently Director & Unit Head – Surgical Oncology, Max Hospital, Gurugram, India, to international doctors in June 2025. He also explained the equivalent advance in colon cancer, complete mesocolic excision with central vascular ligation, and the choice between open, laparoscopic and robotic surgery. How patients are diagnosed and staged before reaching the operating theatre is covered in the complete guide to the diagnosis and management of rectum cancer and in the companion article on the diagnostic workup and staging.

Can rectal cancer surgery avoid a permanent stoma?

Dr. Yadav's message was that, today, normal passage is possible in most cases. A stoma is still sometimes needed, but for most patients it is temporary rather than permanent.

Many patients with rectal cancer fear that their rectum will be removed and that they will have a permanent stoma, with stool and wind passing into a bag attached to the abdomen.

The traditional operation for a low rectal tumour is abdominoperineal resection (APR), which removes the rectum, the anal canal and the sphincters together and leaves a permanent colostomy. A general surgeon in the audience described referring distal rectal tumours that need APR to a colorectal surgeon, and a participant indicated that it is the operation most commonly done for these tumours in their setting. Dr. Yadav's response was that APR is no longer the inevitable answer for a low tumour: it is possible to save the normal passage in most individuals.

The principles of rectal cancer surgery: margins and lymph nodes

Dr. Yadav set out what every rectal cancer operation must achieve, whatever the technique:

1. A clear margin at both ends. The proximal cut in the colon and the distal cut in the rectum must both be free of cancer.
2. A clear circumferential margin. At the lowest level of the tumour, the specimen must be free of all the surrounding muscles, and the mesorectal fascia, the envelope that surrounds the rectum and its fatty tissue, must be intact with a negative margin.
3. Complete lymph node clearance. All the lymph nodes that drain that part of the rectum must be removed.

Total mesorectal excision and the "holy plane"

The principle that makes these goals achievable is followed all over the world. The rectum and its surrounding fatty tissue and lymph nodes, the mesorectum, develop as one unit wrapped in its own fascia. Between that fascia and the pelvic wall lies a natural, largely bloodless plane, known among surgeons as the "holy plane". Removing the rectum and mesorectum as an intact package by dissecting in this plane is called total mesorectal excision (TME), and it is the foundation of modern rectal cancer surgery because it removes the tumour together with its lymphatic drainage.

Dr. Yadav emphasised a feature of rectal cancer biology that explains why this works so well. The cancer tends to spread upwards, along its natural embryological lymphatic supply and embryological planes, rather than downwards. When the surgeon remains strictly within those planes, a very large distal margin is not required.

Sphincter-preserving surgery for low rectal cancer: how low can it go?

A doctor in the audience asked the obvious question: is this really possible for distal rectal cancer? Dr. Yadav's answer was yes, and that this is precisely why he presented the technique.

A tumour lying low in the rectum is not, in itself, the problem. The question is whether the cancer can be removed completely. He made three points:

• A small distal margin is enough. Guidelines have shown that a minimal distal margin of 1 cm is adequate.
• Frozen section confirms clearance. A frozen section is a rapid examination of tissue by the pathologist while the patient is still on the operating table; it can confirm during surgery that all the microscopic cancer cells have been removed.
• The intersphincteric plane is the key. Because the cancer spreads upwards, staying within the embryological planes allows the surgeon to go between the internal and external sphincters of the anal canal, down to the lowest possible point, provided that plane is free of tumour.

When that plane is free, the surgeon can perform a coloanal anastomosis, joining the colon directly to the anal canal, even for tumours in the most distal part of the rectum. This is the role of pelvic MRI before surgery: it shows whether the pelvic muscles and sphincters are free, and therefore whether a sphincter-preserving operation is possible.

How to secure a clear distal margin without frozen section

Many hospitals do not have an intraoperative frozen section service. A doctor in the audience asked how, in that setting, a surgeon can be sure of free margins.

Dr. Yadav's answer rested on technique:

• Follow the natural plane. The correct plane is avascular. Sharp dissection between the internal and external sphincters keeps the surgeon in it.
• Measure the margin on gross examination. For the lowest tumours, aim for at least 1 cm of normal mucosa below the tumour. For tumours higher in the rectum, take a margin of 3 to 5 cm, as far as the location of the tumour allows.
• Confirm with the final pathology. If the surgical planes have been followed, the margin should be negative; the final histopathology report confirms it.

Intersphincteric resection, step by step

Dr. Yadav showed operative photographs and video clips to illustrate the sequence. Upper and middle rectal tumours, he noted, are the easier cases. For low rectal tumours treated by intersphincteric resection, the operation has an abdominal part and a perineal part.

1. Lymph node clearance from above. The lymph node tissue is removed along the aorta up to the origin of the inferior mesenteric artery, the artery supplying the left colon and upper rectum, so that all the draining nodes come away with the specimen.
2. Pelvic dissection. The surgeon then works down deep into the pelvis in the mesorectal plane to the pelvic floor, and from there reaches the space between the internal and external sphincter muscles.
3. Perineal phase. From below, a Lone Star retractor is placed to open the anal canal, and the distal margin is cut under direct vision. Because the surgeon can see exactly where the cut is being made, an adequate margin can be taken.
4. Removal and reconstruction. The specimen is removed completely, and the colon is joined to the anal canal.

Most patients then have a temporary stoma for about three months to protect the join while it heals. After that, in Dr. Yadav's experience, the stoma can be reversed, and the patient passes stool normally.

He was candid that this technique is still not practised in many parts of the world. For a patient with a low rectal tumour, access to a team trained in intersphincteric resection can therefore decide whether the outcome is a permanent stoma or normal bowel function.

Colon cancer: complete mesocolic excision with central vascular ligation

The same principle of operating in embryological planes has changed colon cancer surgery. Dr. Yadav stressed that treatment of a cancer of the caecum or ascending colon is not just a right hemicolectomy, the conventional removal of the right side of the colon.

The technique he uses is complete mesocolic excision (CME) with central vascular ligation (CVL):

• Central vascular ligation: the blood vessels feeding the cancer are tied right at their origin, at their roots, so that all the lymph nodes along them are removed.
• Complete mesocolic excision: the mesocolon, the fatty tissue carrying the colon's blood vessels and lymph nodes, is removed intact within its fascia. On the right side, this includes the retroperitoneal fascia above the duodenum.

In the laparoscopic case he showed, the ileocolic vessels, which arise from the superior mesenteric vessels, were ligated right at their origin, and all the fascia was taken with the specimen. Population-based studies report better disease-free survival with this technique than with a conventional operation, although the RELARC randomised trial found no significant survival advantage over a standard D2 lymph node dissection. Dr. Yadav's team has published its technique in international journals.

Open, laparoscopic or robotic surgery for rectal cancer?

Dr. Yadav compared the three approaches:

• Open surgery still gives good results in colon and rectum cancer.
• Laparoscopic surgery achieves equal results, with the advantages of a shorter hospital stay and better recovery.
• Robotic surgery has, with recent advances, proved equally effective. His team performs colon and rectum cancer surgery with a robotic surgical system at Max Hospital, Gurugram.

In the deep, narrow male pelvis in particular, the magnified three-dimensional view and articulated instruments of a robotic system can make precise dissection in the mesorectal plane easier, which is one reason robotic rectal surgery has spread. The oncological goals, however, are the same whichever approach is used: clear margins, an intact mesorectum and complete lymph node clearance.

Where surgery fits in the wider plan

Surgery is one part of a staged plan. For lower rectal tumours that are T3 or node positive, Dr. Yadav's practice is chemotherapy and radiotherapy before surgery; early T1 or T2 tumours without nodal spread go straight to surgery. In stage 4 disease, limited liver metastases can be removed at the time of the bowel operation or in a second stage, and limited peritoneal disease can be treated with cytoreductive surgery and HIPEC, combined with chemotherapy before and after. The complete guide to rectum cancer explains these decisions in full.

Indicative costs are listed on the treatment-cost pages for colorectal resection surgery, hepatectomy for liver tumours and cytoreductive surgery with HIPEC. Doctors' questions about margins, frozen section and distal tumours are answered on the live discussion page for this masterclass, and related surgical oncology topics are collected on the oncology specialty page.