Can the sphincter be preserved in rectal cancer?

Cancer in the lower rectum does not automatically mean a permanent stoma. If the tumour's distance from the anus, its spread into the muscles, its response to treatment and your bowel control allow it, an operation that preserves the natural passage of stool may be possible.

However, this cannot be determined by centimetres alone. The essential requirement is complete removal of the cancer. Leaving tumour tissue behind to preserve the anal sphincter, the rings of muscle that help hold in wind and stool, is not an acceptable option. Bowel function after surgery also needs to be discussed beforehand.

Why is distance from the anus not enough?

The internal and external sphincters surround the anal canal. The internal muscle works mainly involuntarily, while the external muscle can be consciously contracted to hold in stool. The pelvic floor muscles also support this system. Which tissue layer the tumour has reached affects the extent of surgery.

For example, two tumours close to the anus may lead to different decisions. In one case, healthy tissue remains between the tumour and the muscles; in the other, the tumour has spread into the external sphincter. In the second case, preserving the anus may prevent the surgeon from achieving a cancer-free surgical margin. A clear margin means that there are no cancer cells at the edge of the removed tissue.

The doctor assesses the findings of a finger examination of the rectum, a camera examination inside the bowel and magnetic resonance imaging, or MRI, of the pelvis together. These examinations show the lower edge of the tumour, its relationship to the muscles and its spread into surrounding tissues. It is important to report any existing leakage of wind or stool. This may change the choice of operation.

Comparing the recorded distance with another patient's outcome online often creates false expectations. It is also necessary to know where the measurement was taken from, the length of the tumour and whether it has spread beyond the bowel wall. The decision is not based on a single number.

Low anterior resection and reconnecting the bowel

Low anterior resection is an operation to remove the part of the rectum containing the tumour. Depending on the cancer's location, the surrounding fatty tissue and the lymph nodes within it are also removed. Lymph nodes are small structures in the immune system to which cancer can spread. The remaining colon is joined to the lower part of the rectum.

When the tumour is lower down, the colon may need to be joined directly to the anal canal. This join is called a coloanal anastomosis. For the operation to be possible, the bowel must also reach that point without tension and have an adequate blood supply.

In suitable cases, this operation is performed laparoscopically, using a camera through small abdominal incisions. The Laparoscopic Surgery for Rectal Cancer page explains the general approach. Operating through small incisions does not in itself guarantee that the sphincter can be preserved; that decision depends on the extent of the tumour.

A temporary ileostomy may be created to protect the new join while it heals. This brings the small bowel out onto the abdominal wall. Having this type of stoma does not mean that the anus has been removed. Restoring the natural passage of stool depends on later assessments.

Who may be suitable for intersphincteric resection?

For some very low tumours, part or all of the internal sphincter can be removed while preserving the external sphincter. This is called intersphincteric resection. The surgeon works in the space between the two muscles and joins the colon to the anal canal below.

This approach is not suitable for every low tumour. Important factors include whether the external sphincter and surrounding muscles are free of tumour, whether safe margins can be achieved and the patient's existing bowel control. The more of the internal sphincter that is removed, the greater the concern about reduced function.

A partial resection can be seen in the video Laparoscopic TME with partial intersphincteric resection for distal rectal cancer (unedited video). This is surgical footage intended for adults. The operation shown reflects a specific case; its suitability for another patient cannot be determined without assessment.

Even when the sphincter is preserved, frequent bowel movements, a sudden need to go to the toilet and leakage may occur. Alongside “Will my anus be preserved?”, it is therefore important to ask “What might my day-to-day bowel control be like?” Technical feasibility and daily comfort do not always coincide.

Response to treatment may change the choice of operation

Radiotherapy and drug treatment before surgery may shrink the tumour. When its relationship to surrounding tissues changes, the possibility of sphincter-preserving surgery is reassessed. However, a good response does not automatically guarantee this.

The initial images are also kept and compared with repeat examinations. Distinguishing scar tissue after treatment from remaining tumour is not always easy. The plan is not based only on reduced bleeding or feeling better.

The surgeon should explain in advance when the planned operation might need to change. If a safe join or clear margins cannot be achieved during surgery, a stoma may be necessary. Discussing this possibility reduces the risk of facing an unexpected decision later.

When is a permanent colostomy needed?

If the tumour has spread into the external sphincter or its supporting muscles to the extent that the cancer cannot be fully removed while preserving them, the rectum and anal canal may be removed together. This operation, performed through the abdomen and the perineum, is called abdominoperineal resection. Because the natural outlet is removed, the colon is brought to the abdominal wall to create a permanent colostomy.

Sometimes, even if preserving the muscles is technically possible, severe pre-existing faecal incontinence or conditions that prevent a safe join may make a permanent stoma the more appropriate option. Your daily activities and expectations of treatment are part of this discussion. When a permanent stoma is planned, training in its care is also arranged before surgery.

While waiting for surgery, a complete inability to pass stool or wind, vomiting, increasing abdominal swelling and severe pain require urgent assessment. Heavy bleeding, dizziness or loss of consciousness also mean you should not wait for a scheduled appointment.