Medical Oncologist
CION Cancer Clinics
Left hemicolectomy and sigmoid colectomy: which one and why | CION Cancer Clinics
A left hemicolectomy removes the descending colon, and a sigmoid colectomy removes the S-shaped loop above the rectum. Both take out the tumour with its blood vessels and lymph nodes, then join the bowel again. Where your tumour sits decides which one you are offered. This page explains the difference, what happens before surgery, when a stoma is needed and how bowels settle afterwards. At CION Cancer Clinics, a multidisciplinary team plans colon cancer treatment for your stage, from surgery to chemotherapy and follow-up.
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Medically reviewed by Dr. Muralidhar MuddusettyConsultant Surgical Oncologist · MBBS (AIIMS), MS (Surgery, AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh) · last reviewed October 2026, next review due October 2027
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On this page
- What is the difference between a left hemicolectomy and a sigmoid colectomy?
- Which tumours need a left-sided colectomy?
- How do the two operations compare?
- What happens before a left-sided colectomy?
- The words you will meet, in plain language
- Will you need a stoma, and how will your bowels work?
- What this page cannot tell you
- Common questions about left-sided colon surgery
The short answer
What is the difference between a left hemicolectomy and a sigmoid colectomy?
Both operations remove cancer from the left side of the colon. A left hemicolectomy takes out the descending colon, the part running down the left side of the belly. A sigmoid colectomy takes out the sigmoid colon, the S-shaped loop just above the rectum.
Why there are two operations
Colon cancer spreads first to the lymph nodes, the small glands that sit beside the arteries feeding the bowel. The surgeon removes the tumour together with those arteries and nodes in one piece. The descending colon and the sigmoid colon are fed by different branches, so the piece removed differs. Where the tumour sits on your colonoscopy and CT scan decides which operation you are offered.
How the bowel is joined again
After a left hemicolectomy, the transverse colon is joined to the lower colon. After a sigmoid colectomy, the descending colon is joined to the top of the rectum. This join is called an anastomosis. The surgeon often frees the bend near the spleen so the two ends meet without stretching.
For the full map of which operation suits which part of the colon, see which operation for which location.Where the tumour sits
Which tumours need a left-sided colectomy?
Left-sided tumours more often change bowel habits or cause visible blood, because stool is firmer here and the bowel is narrower.
Splenic flexure
The bend near the spleen sits between two blood supplies. Surgeons may choose a left hemicolectomy, a smaller segmental resection, or an extended operation, depending on the tumour and your health.
Descending colon
This is the classic reason for a left hemicolectomy. The descending colon and its nodes are removed, and the transverse colon is brought down to make the join.
Sigmoid colon
The sigmoid is a common site for colon cancer. A sigmoid colectomy removes the loop with its main artery and nodes. Diverticular disease can look similar on a scan, so the biopsy matters.
Where sigmoid meets rectum
A tumour at this junction raises one key question: is it colon or rectal cancer? An MRI of the pelvis often settles it, because rectal cancer may need radiation before surgery.
Why it matters
- It changes the operation offered
- It changes whether radiation comes first
- It changes which specialist pages apply
Not sure whether this applies to you?
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How do the two operations compare?
Left hemicolectomy
Sigmoid colectomy
For tumours of the descending colon
For tumours of the sigmoid loop
Removes the descending colon and splenic bend
Removes the sigmoid colon and its main artery
Transverse colon joined to lower colon
Descending colon joined to the upper rectum
Usually done by keyhole surgery
Usually done by keyhole surgery
From report to operation
What happens before a left-sided colectomy?
Colonoscopy and biopsy
CION arranges the colonoscopy through a diagnostic partner. The tumour is sampled and marked with a small ink tattoo so the surgeon can find it from outside the bowel.
Staging scans
A CT scan of the chest, abdomen and pelvis checks the liver, lungs and nodes. A pelvic MRI is added when the tumour is low in the sigmoid. A CEA blood test gives a starting value.
The tumour board decides
Surgeons, medical oncologists and radiologists review the scans together. If the bowel is nearly blocked, they consider whether a stent before surgery is safer than operating straight away.
Surgery and the pathology report
CION's surgical oncologists plan the operation, and it is carried out at an accredited partner hospital. The pathology report then decides whether chemotherapy after surgery is advised.
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The words you will meet, in plain language
- Splenic flexure mobilisation
- Freeing the bend near the spleen so the colon reaches down to the join without tension. It does not mean the spleen is removed.
- High tie
- Dividing the main artery to the left colon close to its origin, so the lymph nodes along it come out with the specimen.
- Colorectal anastomosis
- The join between the colon and the top of the rectum after a sigmoid colectomy. It may be stapled or stitched.
- Hartmann's procedure
- Removing the tumour, closing the rectal stump and bringing the colon out as a colostomy, usually in an emergency.
- Lymph node yield
- How many nodes the pathologist found. Guidelines ask for at least twelve so the stage can be trusted.
- Margin
- The healthy tissue at the cut ends. A clear margin means no cancer cells reach the edge.
After the operation
Will you need a stoma, and how will your bowels work?
Most people having a planned left hemicolectomy or sigmoid colectomy do not need a stoma. The bowel is joined in the same operation and stool passes the normal way. Your surgeon will tell you beforehand if a stoma is likely.
When a colostomy is made
In an emergency, such as a blocked or burst bowel, joining inflamed or swollen bowel is risky. The surgeon may remove the tumour and bring the colon out as a colostomy. This is called a Hartmann's procedure, and it can often be reversed months later. The pages on emergency surgery for a blocked colon and whether you will need a stoma explain more.
Bowel habits at home
In the early weeks, motions are often more frequent, smaller or come in clusters. Most people settle gradually. Soft rice, dal, curd and cooked vegetables are gentle choices while the join heals.
Fever, worsening belly pain or vomiting after you go home needs a call to the surgical team the same day.Being straight with you
What this page cannot tell you
It cannot tell you which operation is right for you. That depends on the exact tumour position, any spread on your scans, your fitness and your other illnesses. The tumour board weighs these, and the surgeon explains the reasoning at your consultation.
Who this does not apply to
It does not cover tumours of the caecum or ascending colon, which need a right hemicolectomy. It does not cover cancer of the rectum, which is planned differently. People with an inherited condition such as Lynch syndrome or FAP may be offered a larger operation. An early cancer inside a polyp may sometimes be removed through the colonoscope instead.
It cannot read your report
Node counts, margins and vessel findings need an oncologist to read them in context. Bring the report and the scan discs to your appointment.
If you have been told you need this operation and want a second look at the plan, the helpline can arrange a tumour board review.Questions we are asked
Common questions about left-sided colon surgery
Is a sigmoid colectomy the same as an anterior resection?
They overlap. When the join is made at the top of the rectum, surgeons sometimes call it a high anterior resection. The name matters less than where the tumour is and how much bowel is removed. Ask your surgeon to draw it for you.
How long will I stay in hospital?
Most people go home within about a week after a planned keyhole operation. Older patients, open surgery or a complication can mean a longer stay. You are encouraged to walk, drink and eat early, because that speeds recovery.
Is a leak more likely on the left side?
A join on the left side, especially close to the rectum, carries a somewhat higher leak risk than a right-sided join. It is still uncommon. Fever, worsening pain and a fast pulse are warning signs. The leak page explains what happens next.
Can a Hartmann's colostomy be reversed?
Often, yes. Once you have recovered and any chemotherapy is finished, the surgeon can rejoin the bowel in a second operation. Not everyone is fit for it, and some people choose to keep the colostomy. Your surgeon will discuss the timing with you.
My scan says diverticulitis. Could it be cancer?
The two can look alike on a CT scan of the sigmoid. That is why a colonoscopy is usually advised once the inflammation settles. Most people with diverticular disease do not have cancer, but the colonoscopy answers the question properly.
Will I need chemotherapy afterwards?
It depends on the pathology report. Cancer in the lymph nodes usually means chemotherapy is advised. Some node-negative cancers with high-risk features may also benefit. The medical oncologist explains this once the report arrives and you have recovered.
Does CION perform the surgery itself?
No. CION's surgical oncologists assess you and plan the operation, and it is carried out at an accredited partner hospital. Chemotherapy, follow-up and surveillance continue at your CION centre, so the same team stays with you throughout.
Will my bowel ever feel normal again?
For most people, yes. The remaining colon adapts and habits settle over the following months. A few people keep some urgency or frequency. Simple diet changes and medicines usually help, so mention it at follow-up rather than putting up with it.
Your Specialists
Meet CION's colon cancer specialists. Bring your colonoscopy, scan or biopsy report.
Our surgical and medical oncologists plan colon cancer care together: which operation, whether chemotherapy is needed, and the follow-up that comes after.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
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Sources
- American Cancer Society — Colon Cancer Surgery
- National Cancer Institute — Colon Cancer Treatment
- NHS — Colostomy
- NHS — Diverticular disease and diverticulitis
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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