Colorectal cancers
Cancers of the colon and rectum, including sphincter-sparing surgery that avoids a permanent stoma bag wherever it is safe.
What are colorectal cancers?
The colon (large bowel) and rectum (the last part of the bowel) absorb water and store waste. Cancers here usually grow slowly from small growths called polyps.
Warning signs
- Blood in the stool or bleeding from the back passage
- A change in bowel habit lasting more than three weeks, such as constipation, loose stools, or a feeling that the bowel has not emptied
- Pain or a lump in the abdomen
- Losing weight without trying
- Tiredness caused by low haemoglobin (anaemia)
How it is diagnosed
- Colonoscopy: a camera examination of the whole large bowel, with a biopsy of any growth
- CT scan of the chest, abdomen and pelvis to check for spread
- MRI of the pelvis for rectal cancer, to plan treatment in detail
- CEA blood test, a tumour marker used before and after treatment
Treatment
- Colon cancer is usually treated with surgery to remove the affected part of the bowel and its lymph nodes. Some patients also need chemotherapy afterwards.
- Rectal cancer often starts with radiotherapy and chemotherapy to shrink the tumour, followed by surgery. Whenever it is safe, the surgery keeps the anal sphincter so that you can pass stools normally.
Sphincter-sparing surgery for rectal cancer
The anal sphincter is the ring of muscle that controls when you pass stools. In the past, many rectal cancers close to the anus were treated by removing the sphincter, which meant a permanent stoma bag on the abdomen.
Today, most patients can keep their sphincter. Depending on how close the tumour is to the anus, the operation may be:
- a low anterior resection, which removes the affected part of the rectum and joins the bowel back together
- an ultra-low anterior resection, for tumours lower down
- an intersphincteric resection, for tumours very close to the anus, which removes only the inner layer of the sphincter muscle
A temporary stoma is often made to protect the join while it heals, and it is closed a few months later. A permanent stoma is needed only when keeping the sphincter would not remove the cancer safely or would leave poor control.
Robotic and keyhole surgery
Most bowel cancer operations can be done through small cuts. Robotic surgery is especially useful for rectal cancer, because the rectum sits deep in a narrow pelvis. The robot’s magnified 3D view and flexible instruments help the surgeon work precisely around the nerves that control the bladder and sexual function.
Life after surgery
Many people notice changes in their bowel habits after surgery for rectal cancer, such as urgency or needing to go more often. This is called low anterior resection syndrome (LARS). It often improves over months, and diet changes, medicines and pelvic floor exercises help.
Dr. Suraga is the lead author of a 2026 study of LARS after sphincter-preserving surgery. The study looked at which factors predict LARS and how it affects patients’ satisfaction with their bowel function.
Common questions
I have blood in my stool. Is it just piles?
It may be, but you cannot tell on your own. Bleeding from the back passage, especially after the age of 40 or with a change in bowel habit, should be examined. A colonoscopy may be needed.
Will I need a stoma bag?
Most people do not need a permanent stoma. After surgery for rectal cancer, a temporary stoma is sometimes made to protect the join while it heals, and it is usually closed a few months later.
Can colorectal cancer be found early?
Yes. A colonoscopy can find cancer early and remove polyps before they turn into cancer. Ask your doctor when to start, especially if a parent, brother or sister has had bowel cancer.