Anterior Resection

What is an anterior resection?

An anterior resection removes a diseased section of your large bowel — specifically the sigmoid colon (the lower S-shaped section of bowel) and/or rectum (the last part of your bowel before the anus). Once that section is taken out, the two healthy ends are joined back together. This join is called an anastomosis. The most important thing to understand is that your anus and the muscles around it are completely left in place — so after you have healed, you will still be able to go to the toilet in the normal way, through the back passage.

Depending on how far down your bowel the join needs to be made, this is described as a high anterior resection (upper section of rectum), low anterior resection (middle to lower rectum), or ultra-low anterior resection (very close to your sphincter muscles — the muscles that control your anus). When the join is low down, Mr Nguyen will often also create a temporary loop ileostomy — a small opening on the surface of your tummy where stool exits into a bag, completely bypassing the new join while it heals. This is there to protect you, not because anything has gone wrong. It is not permanent: usually 8–12 weeks later, once the join is confirmed to be fully healed, a shorter second operation closes the ileostomy and restores your normal bowel route.

If you have rectal cancer, the operation includes a technique called total mesorectal excision (TME) — a term worth understanding. It means Mr Nguyen removes not just the tumour but the entire wrapped package of tissue and lymph nodes (small glands that filter fluid from your body) that surround the rectum, all in one intact piece. This is the gold-standard approach, and it is the single most important technical step in reducing the chance of the cancer coming back in the same area. Mr Nguyen uses robotic or laparoscopic (keyhole) tools specifically because they give greater precision in this delicate part of the operation.

Who needs this operation?

You may be having this operation for one of the following reasons:

• Rectal cancer — cancer of the upper, middle, or lower rectum, in situations where the sphincter muscles can be safely preserved and kept working
• Sigmoid colon cancer — cancer in the lower S-shaped curve of your large bowel
• Complex or large polyps in the sigmoid colon or rectum — growths that are too large or positioned in a way that makes them too risky to remove safely through a camera (endoscope) alone
• Complicated diverticular disease — small pouches (called diverticula) can form in the bowel wall over time. When they cause problems — repeated or severe infections, an abnormal connection to another organ (called a fistula), a narrowing of the bowel from scarring (a stricture), or a burst pouch causing a localised pocket of infection — surgery is sometimes the right answer
• Bowel obstruction or narrowing — a blockage or stricture in the sigmoid colon or upper rectum that is causing symptoms and needs surgical correction
• Rectal prolapse — when your rectum slides through the anus and protrudes outside the body. If this keeps happening, surgery (sometimes called resection rectopexy) can anchor and repair it

How is it performed?

You will be under general anaesthetic — fully, comfortably asleep — for the entire operation, which takes around 2.5–4 hours depending on how far down the bowel the new join needs to be made.

Keyhole (laparoscopic or robotic) approach

In most cases, Mr Nguyen performs this operation using keyhole surgery — either laparoscopic (a camera and thin instruments through 4–5 small cuts in your abdomen) or robotic (using the da Vinci robotic system, which gives a high-definition 3D magnified view and instruments that can bend and rotate in ways ordinary surgical tools cannot). At no point is your abdomen opened with a large incision. One of the most important parts of this operation is carefully identifying and protecting the nerves that run very close to the rectum — these are the nerves that control your bladder and sexual function. Mr Nguyen works with great precision to avoid disturbing them.

The join (anastomosis)

Once the diseased section of bowel has been removed, the two healthy remaining ends are joined back together using a circular stapling device — this is the anastomosis, your new reconnection point. Before closing, Mr Nguyen checks the join thoroughly to confirm it is completely watertight. That check matters.

Temporary bag (defunctioning ileostomy)

If your join is low down in the pelvis (close to your anus), or if you had radiotherapy before surgery — which can affect how tissues heal — Mr Nguyen will also create a temporary loop ileostomy. This is a small opening on the surface of your tummy where stool exits into a bag, completely bypassing the new join while it heals over the coming weeks. It is one of the most important ways your surgeon protects you. It is not permanent: typically 8–12 weeks after surgery, a test is done to confirm your join has healed fully, and then the ileostomy is closed in a separate, shorter operation — see closure of ileostomy for more about that procedure.

Before the operation

• An MRI scan of your pelvis (for rectal cancer, this gives detailed pictures of the tumour and surrounding structures) and a CT scan of your chest, abdomen, and pelvis to get a full picture of your body before surgery
• If a temporary stoma (bag) is likely, a stomal therapy nurse will meet with you beforehand, mark the best spot on your tummy, and walk you through exactly how the bag works, looks, and is managed day-to-day — so there are no surprises on the day
• A carbohydrate-loading drink the night before and morning of surgery — this is a specially formulated sugary drink that helps prime your body to cope with the physical stress of a major operation
• A walk-through of what to expect before, during, and after surgery as part of an enhanced recovery programme — a structured approach that helps you recover faster and get home sooner

What to expect on the day

Here is what the day of your operation will look like, step by step:

• You will be admitted in the morning. A drip (an IV line) will be placed in your arm. You will receive a dose of antibiotics to reduce infection risk, and a blood-thinning injection to protect against clots forming in your legs
• The operation itself takes 2.5–4 hours. Afterwards you will spend 1–2 hours in the recovery room, where the nursing team will closely monitor you while the anaesthetic wears off, before you are moved to the ward
• On the ward you will have a urinary catheter (a soft, thin tube that drains your bladder automatically — you will not feel it and it is entirely routine after this type of operation), a drip for fluids, and good pain relief. Pain is usually managed with either an epidural (medication delivered directly near your spine — very effective) or a patient-controlled pump that lets you give yourself a dose of pain relief whenever you need it by pressing a button
• If a stoma was formed during your operation, a stomal therapy nurse will come to see you on the first day after surgery. They are specialists in this area and will help you get comfortable and confident with the bag at whatever pace works for you
• Small sips of water usually start on the day of surgery or the day after. Food is gradually introduced over 2–3 days as your bowel wakes up
• Getting out of bed and taking a short walk from day 1 is genuinely one of the most helpful things you can do — it wakes the bowel up, reduces the risk of blood clots in your legs, and has been shown to speed up recovery. The team will help you

Recovery

In hospital (4–7 days): Your stay will typically be a few days — slightly longer if your join was made lower down. The urinary catheter is usually removed on day 2 or 3. Your bowel (or your stoma, if you have one) will start to show activity within 2–4 days. You will be ready to go home once you are eating comfortably, your pain is well controlled with tablets alone, and — if you have a stoma — you feel confident enough to manage it yourself at home. No one rushes you out the door before you are ready.

Once you are home:

• Weeks 1–4: Rest is important in the first week, then gradually increase what you do each day at your own pace. Your wound sites will be checked at 1–2 weeks. If you have a stoma, a stomal therapy nurse will stay in close contact with you during this period — you are not navigating this alone.
• Weeks 4–6: Most people are ready to return to a desk job and start driving again around this point — provided you are off strong pain medication and can react quickly in an emergency. Continue to avoid any heavy lifting for 6 weeks from your surgery date to protect your abdominal wall while it heals.
• 8–12 weeks: If you had a temporary stoma, a special X-ray test called a gastrografin enema is done around this time. A small amount of contrast dye (a harmless liquid that shows up on X-ray) is gently introduced from below, and images are taken to confirm your join has healed completely. If it has, the ileostomy reversal operation is then planned — this is a shorter, simpler procedure than the original surgery.
• Your bowel habits after surgery: If your join was made lower down, it is entirely normal and expected that your bowel will not behave quite the same as it did before, particularly in the first year. Many people experience what is called low anterior resection syndrome (LARS) — this can mean going to the toilet more often, needing to rush, passing several small motions in a row (called clustering), or having difficulty distinguishing wind from stool. LARS affects a significant number of people with low joins and is not a sign that anything has gone wrong. For most people it gradually improves over 12–24 months. Pelvic floor physiotherapy (exercises to retrain the muscles around your bowel and bladder) and dietary adjustments can make a real and meaningful difference — Mr Nguyen's team will guide you through this.
• A follow-up appointment with Mr Nguyen is arranged 2–6 weeks after your operation — this review is at no charge to you

Your cancer pathology results (histology — what the laboratory found when they examined the removed tissue) are usually ready within 2 weeks and will be discussed at your follow-up appointment. After that, Mr Nguyen will arrange an ongoing surveillance programme — typically a check-up at least every six months — including clinical reviews, CT scans, CEA blood tests (a tumour marker), and periodic colonoscopy, to monitor your recovery and catch anything early if it ever needed attention.

Risks and complications

This is a major operation, and it is completely reasonable to want to understand the risks clearly before you go ahead. Mr Nguyen will walk through all of these with you in detail at your pre-operative appointment — please bring any questions you have. Here is an honest summary.

Common

• Wound infection or haematoma (bruising under the skin) — the small keyhole wound sites can occasionally become infected or develop a tender, swollen area under the skin. Both are easily managed with antibiotics or simple wound dressings, and neither is a setback to your overall recovery.
• Urinary retention — your bladder can sometimes be slow to start working properly again after pelvic surgery, because of how close together the nerves are in that area. The catheter may need to stay in a little longer than planned until things settle down. This almost always resolves fully on its own.
• Post-operative ileus — your bowel may take a few extra days to "wake up" and start moving again after surgery. This is common after any abdominal operation. It is managed with fluids, regular walking, and patience — you will be encouraged to move around as soon as possible, which genuinely helps.

Less common

• Anastomotic leak — this is when the join between the two ends of bowel does not seal completely and some bowel fluid leaks out. It happens in around 5–10% of low joins and less often with joins made higher up. If you have a temporary stoma, it already protects you from the most serious consequences of a leak — your stool is being diverted away from the join entirely. A significant leak may need antibiotics, a drain placed under CT guidance, or occasionally a further operation. Your care team watches for any signs of this closely in the first few days after surgery.
• Pelvic collection or abscess — a pocket of infection can occasionally form deep inside the pelvis after surgery. This is usually treated by placing a small drain under CT scan guidance — a straightforward procedure that in most cases avoids the need for a return to theatre.
• Changes to sexual function — the nerves that control erections and ejaculation in men, and vaginal sensation and lubrication in women, run very close to the rectum. In a proportion of patients these nerves are affected by the surgery — the risk ranges from around 5–30% depending on how low down the operation is performed and whether you had radiotherapy beforehand. Mr Nguyen uses nerve-sparing techniques specifically designed to minimise this risk, and will discuss the relevant risk for your particular situation before surgery.
• Bladder function — some patients find it harder to fully empty their bladder for a few weeks after surgery, again because of the nearby nerve relationships. This usually improves on its own within weeks to months.
• DVT or PE (blood clot) — a clot in a leg vein (deep vein thrombosis) or, more seriously, in the lungs (pulmonary embolism). To reduce this risk, you will be given blood-thinning injections, compression stockings, and encouraged to walk as early as possible after surgery. These steps together make clots much less likely.

Rare

• Ureteric injury — the ureters (the thin tubes that carry urine from your kidneys to your bladder) run close to the surgical field. They are carefully identified and protected at every step; injury is rare, but it is a recognised risk of any pelvic operation.
• Permanent stoma — in a small number of cases, if serious complications arise with the join, or if it becomes clear that your sphincter muscles are not strong enough to reliably control bowel movements, a permanent stoma may be needed. This is uncommon, and it would always be discussed openly and thoroughly with you before any such decision was made — it would never come as a surprise.

Frequently asked questions

Related patient guides

These articles are written for you and your family — explaining symptoms, what to expect, and what recovery looks like in plain language.