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Anastomotic leak: what it is and why it matters | CION Cancer Clinics
An anastomotic leak happens when the join made between two ends of the bowel, stomach or food pipe after surgery does not seal fully, and gut contents escape inside the body. It can cause a serious infection, so worsening pain, fever, a fast heartbeat or changed drain fluid need same-day attention. This page explains which operations carry the risk, what raises it, and how a leak is found and treated. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
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Medically reviewed by Dr. Muralidhar MuddusettyConsultant Surgical Oncologist · MBBS (AIIMS), MS (Surgery, AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh) · last reviewed September 2026, next review due September 2027
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The short answer
What is an anastomotic leak, and why does it matter?
An anastomotic leak is when the join made between two ends of the bowel, stomach, food pipe or another tube after surgery does not seal fully, and gut contents escape into the body. It matters because that fluid causes infection, and a leak that is found late can make a person seriously ill.
What the join is
When a surgeon removes a section of the gut containing a cancer, the two remaining ends are usually joined with stitches or staples. That join is called an anastomosis. Over the following days the body heals it into a watertight seal, in the same way a cut on the skin knits together.
Why a join sometimes fails
Healing needs a good blood supply, no tension on the join, and a body well enough nourished to repair itself. If any of those is missing, part of the join can break down. This can happen even when the surgery was done carefully and correctly.
When leaks usually show
Most leaks show in the first week or so after surgery, often while you are still in hospital. Some appear later, after you have gone home. That is why the warning signs below matter to the family as much as to the ward.
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Signs of a leak that cannot wait
After any operation that joined the gut, go to the nearest emergency department the same day, or tell the nurse at once if you are still in hospital, if there is belly or chest pain that is getting worse instead of better, a fever or shivering, a fast heartbeat, fast breathing, new confusion, vomiting, or drain fluid that turns cloudy, brown or looks like stool. Say which operation was done and when. Do not wait to see whether it settles.
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Which operations can lead to a leak?
A leak can only happen where a join was made. If your operation did not involve one, this complication does not apply to you.
Food pipe surgery
After an oesophagectomy, the stomach is usually pulled up and joined to the remaining food pipe in the chest or neck. A leak here can cause chest pain, breathlessness and fever.
Stomach surgery
After part or all of the stomach is removed, a loop of small bowel is joined to what remains. A leak usually shows as upper belly pain and fever.
Bowel and rectal surgery
Joins low down in the rectum, close to the back passage, are the ones most at risk. The surgeon may make a temporary stoma to protect them while they heal.
Pancreas surgery
After a Whipple operation, several joins are made. A leak from the pancreas join releases digestive juices, which need careful draining.
Bladder surgery
When a new urine pathway is made from a piece of bowel, urine can leak from the joins. It is usually treated with drains and tubes.
Your own risk
What makes a leak more likely?
The site of the join matters most. Joins in the food pipe and low in the rectum carry more risk than joins higher in the bowel. Your surgeon can tell you where your join will be and what that means for you.
Things about your health
Smoking, poorly controlled diabetes, heavy weight loss and poor nutrition, long-term steroid use, and heart or lung disease that lowers the blood supply to tissues all make healing harder. Radiotherapy to the area before surgery can also slow healing of the join.
What can be done beforehand
Stopping smoking, eating well, and bringing blood sugar under control before surgery can help. Some people are given nutrition drinks or feeds for a period first. Ask your team whether this would suit you, as not every cancer can safely wait.
Why a temporary stoma is sometimes made
For a low rectal join, the surgeon may bring a loop of bowel out onto the belly for a few months. The stoma does not stop a leak happening, but it makes one far less harmful. It is usually closed in a later, smaller operation. Ask whether this is planned before you consent.
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If a leak is suspected
How is a leak found and treated?
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Blood tests and examination
Rising infection markers in the blood, a fast pulse and a tender belly raise the question. Drain fluid is looked at closely.
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A scan
A CT scan, sometimes with a drink or dye that shows up on the pictures, is the usual way to see whether fluid is escaping from the join.
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Resting the gut and antibiotics
A small, contained leak may heal on its own with antibiotics, no food by mouth for a time, and nutrition through a drip or a feeding tube.
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Draining the collection
If fluid has gathered, a radiologist may place a thin drain through the skin under scan guidance, without another operation.
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A camera procedure
For some leaks in the food pipe or stomach, a stent or other device can be placed from inside using an endoscope. Ask your centre whether this is available to you.
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A return to theatre
A large leak, or one making the person very unwell, may need another operation. The join may be repaired, or the bowel brought out as a stoma so the area can heal.
Words you may hear
What do the words the doctors use mean?
- Anastomosis
- The join between two ends of the gut or another tube, made with stitches or staples.
- Collection
- A pocket of fluid or pus that has gathered inside the body, often near the join.
- Contrast study
- An X-ray or CT taken after you swallow, or are given, a liquid that shows up on the pictures, to see whether it escapes.
- Defunctioning stoma
- A temporary opening of the bowel onto the belly, made to divert stool away from a join while it heals.
- Nil by mouth
- Nothing to eat or drink, so the join can rest.
- Sepsis
- An infection that has started to affect the whole body. It needs urgent treatment.
Commonly believed
What do families often believe about a leak?
"A leak means the surgeon did the join badly."
Leaks happen in the hands of experienced surgeons too, because healing depends on blood supply and the body's condition as well as the stitching. What matters is spotting it early and treating it quickly.
"The pain is just from the operation, so we should not bother the nurse."
Pain after surgery should slowly get better. Pain that is getting worse, especially with fever or a fast heartbeat, is exactly what the team needs to hear about straight away.
"A leak always means another big operation."
Many small leaks heal with antibiotics, resting the gut and a drain placed under scan guidance. A second operation is needed when these are not enough.
"If they gave a stoma, the cancer must be worse than they said."
A temporary stoma is often planned to protect a low join while it heals. It says more about where the join sits than about the cancer. Ask the surgeon why it was made.
Questions we are asked
Common questions about anastomotic leaks
What are the first symptoms of an anastomotic leak?
Often a fever, a fast heartbeat and pain that is getting worse rather than better. Some people feel generally unwell, confused or breathless before any pain. Drain fluid may turn cloudy, brown or smell bad. After food pipe surgery, chest pain and breathlessness can be the first signs.
How common is a leak?
It depends mainly on where the join is. Joins in the food pipe and low in the rectum leak more often than joins higher in the bowel. Your health before surgery also matters. Ask your surgeon for the range that applies to your own operation, rather than relying on a figure found online.
Can a leak happen after we have gone home?
Yes, although most show while you are still in hospital. If pain returns or worsens at home, or you develop a fever, vomiting or feel very unwell, go to the nearest emergency department the same day and tell them what operation you had and when.
Will a leak affect the cancer treatment?
It can delay chemotherapy or radiotherapy after surgery, because the body needs to recover first. Your oncologist will weigh the delay against your recovery and explain what it means for your plan. A leak does not change what the cancer is or what the pathology report shows.
How long does a leak take to heal?
It varies widely. A small, contained leak may heal over days to weeks with antibiotics and drainage. A larger one can mean a longer hospital stay, feeding support and sometimes another operation. The team will give you a clearer idea once they know the size and site.
Why can I not eat if there is a leak?
Food and drink passing over the join can keep pushing fluid out through it. Resting the gut gives the join a chance to seal. Nutrition is still given, through a drip or a feeding tube, because the body needs energy and protein to heal.
Can a leak be prevented completely?
No operation can remove the risk entirely. Stopping smoking, eating well, controlling diabetes and following advice on walking and breathing exercises all help the body heal. For some joins, the surgeon may plan a temporary stoma to make any leak far less harmful.
What should we ask the surgeon before the operation?
Ask whether a join will be made, and where. Ask how often leaks happen after this operation in their patients, whether a temporary stoma may be needed, how a leak would be picked up, and who to call at night after discharge. These are fair questions and a surgeon should expect them.
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Sources
- Cancer Research UK — Surgery for bowel cancer
- Cancer Research UK — Surgery for oesophageal cancer
- NHS — Sepsis
- American Cancer Society — Cancer surgery
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