Surgery of Colon and Rectal Cancers

Colorectal cancer refers to malignant tumors and growths in the large intestines or the rectum, which can cause abdominal pain, rectal bleeding and a change in bowel habits. No two cases of cancer are identical, and treatment depends mainly on the cancer’s stage and the patient’s overall health. Left untreated, the cancer may spread to other organs.

How Is Surgery Performed?

Colon Cancer Surgery

Before the procedure, the patient will be given bowel preparation to flush out and clean the inside of the bowels. This is to ensure that no stool is left in the colon for the surgery. This process is typically performed before colonoscopies and surgeries.

Polyps found in the earliest stage of colon cancer can be removed via colonoscopy:

  • Polypectomy:

    A wire loop is inserted into the colon through the rectum to cut off the polyp with electric currents.

  • Local Excisions:

    Through colonoscopy, special instruments can be used to get a sample of the colon, or remove polyps.

For large and numerous tumors, or if the cancer has spread to the entire organ, the preferred treatment is colectomy. This involves removing part or the entire colon, including the lymph nodes. It can be done in two ways:

  • Open Colectomy

    The operation is done traditionally. The colon is accessed through a long incision on the abdomen.

  • Laparoscopic Colectomy

    This procedure involves smaller incisions through which a viewing instrument and small surgical tools are inserted.

Rectal Cancer Surgery

For rectal cancer, surgery may be done before or after chemotherapy and radiation therapy. Just like in colon cancer, polypectomy and local excisions via colonoscopy can be performed to remove polyps.

Surgery methods used to treat rectal cancer in all stages include:

  • Local Transanal Resection:

    Suitable for small tumours located near the anus, this method involves the insertion of instruments through the anus and into the rectum to access the tumor site. The procedure is done under sedation or general anaesthesia. Additional radiation therapy is prescribed in cases where the cancer has already spread to the lymph nodes.

  • Transanal Endoscopic Microsurgery:

    Similar to local transanal resection, this procedure uses a special magnifying scope and microsurgical instruments to remove tumors from the rectum through the anus.

  • Anterior Resection:

    This procedure is done under general anesthesia and involves removing the upper part of the rectum with the tumor. The remaining part of the rectum will be attached to the colon to facilitate normal bowel movement. This method is most rectal cancers.

  • Total Mesorectal Excision:

    Like low anterior resection, total mesorectal excision involves removing the entire rectum containing the tumor. The colon is directly connected to the anus for bowel movement. It is usually performed laparoscopically. In some cases, a stoma may be created after surgery.

  • Abdominoperineal Resection:

    Typically used to treat tumors found in the lower part of the rectum or anus, this procedure involves the surgical removal of the rectum, anus and sigmoid colon. It is usually performed via laparoscopy surgery using four to five small cuts. Abdominoperineal resection results in a permanent colostomy to help the body excrete stools.

  • Pelvic Exenteration:

    This is a major operation that involves the removal of the pelvic cavity, including the anus, rectum, urinary bladder and parts of the reproductive organ. Colostomy and urinary diversion are required after the surgery.

After the operation, the patient needs to meet with the doctor for follow-up examinations and testing to ensure that all cancer has been removed.

Following the operation there will be initial pain, which can be relieved using prescribed pain medicines. The patient is also discouraged from eating, or consuming solid food, a couple of days after the surgery to allow the bowels to heal.

In very rare cases, where the colon is reattached to the rectum or anus, there may be a leak stemming from a reopened incision. Another round of surgery will be conducted to fix the leak or close the wounds.

Scar tissues may develop, causing the organs and tissues to attach to each other.

Other forms of side effects such as bleeding and blood clots can develop depending on several factors, including the patient’s health and the manner by which the operation was conducted.

However, these risks will be greatly minimized if the procedure was performed by a certified and experienced colorectal surgeon.

Colorectal Practice’s Dr Dennis Koh is a fully qualified and trained colorectal surgeon specializing in the comprehensive and multidisciplinary management of colorectal conditions. To find out more about colon and rectal cancers, call +65 6262 1226 or email us at

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