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Anastomotic leak after colectomy: the signs and what happens next | CION Cancer Clinics
An anastomotic leak is when the join made between two ends of bowel during a colectomy does not hold, and bowel contents escape into the tummy. It usually shows in the first week or two as new or worsening tummy pain, fever, a fast heartbeat and feeling much more unwell than the day before. This page explains the signs, who is at higher risk, what the team does, and what to ask before the operation. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
MI
Medically reviewed by Dr. Mohammed ImaduddinConsultant Surgical Oncologist · MBBS, MS (General Surgery), MCh (Surgical Oncology) · last reviewed September 2026, next review due September 2027
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The short answer
What is an anastomotic leak, and what does it feel like?
An anastomotic leak is when the join made between two ends of bowel during a colectomy does not hold, and bowel contents escape into the tummy. It usually shows itself in the first week or two after the operation as new or worsening tummy pain, fever, a fast heartbeat and feeling much more unwell than the day before. It needs urgent attention from the surgical team.
What the join is
When a piece of colon is removed, the surgeon joins the two healthy ends with stitches or staples. That join is called an anastomosis. It has to heal from the inside like any wound, and for the first days it is held together by the stitches alone. A leak happens when the join breaks down, in a small spot or along a length, before it has sealed.
Who it happens to
It happens to a minority of people after bowel surgery, and it is more likely when the join is low in the pelvis near the back passage, when the person smokes, is very underweight or overweight, has diabetes, has had radiotherapy to the area, or was on steroids. It is the complication surgeons watch for most closely in the first days.
A temporary stoma is often made at the first operation precisely to protect a join at higher risk. It does not stop a leak, but it makes one far less dangerous.
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One thing that cannot wait
In the first weeks after a colectomy, new or worsening tummy pain with a fever, a racing heart, vomiting, a swollen hard tummy, or a sudden change in what comes from the wound or drain, needs same-day care. Go back to the hospital that did the operation or to the nearest emergency department, and say you have just had bowel surgery. Do not take paracetamol and wait to see, because it hides the fever.
Not sure whether this applies to you?
Ask an oncologistThe signs
What are the symptoms of a leak?
A leak rarely announces itself with one dramatic sign. It is usually a person who was getting better and then stops.
Pain that changes
Pain after surgery should ease each day. Pain that gets worse, moves to a new place, spreads across the whole tummy, or makes the tummy hard and tender to touch is the commonest first sign.
Fever and a fast pulse
A temperature that rises after the second or third day, shivering, or a heart rate that stays high at rest, often comes before the pain is obvious. Nurses check these several times a day for this reason.
Changes at the drain or wound
If a drain is in place, fluid turning cloudy, brown, foul-smelling or looking like bowel contents is a strong sign. So is pus or bowel fluid from the wound itself.
Many leaks happen with no drain in place. The absence of a drain sign proves nothing.Not progressing
Not passing wind, a swollen tummy, vomiting, going off food again, breathlessness, confusion in an older person, or simply looking grey and unwell. Families often notice this before anyone else.
If a leak is suspected
What happens next?
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Examination and blood tests
The surgeon examines the tummy and checks blood tests for signs of infection. A rising infection marker in the first days is one of the earliest clues.
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A CT scan with contrast
This is the usual test. Dye is given, sometimes also through the back passage, and the scan looks for fluid, gas or a collection outside the bowel near the join.
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Antibiotics and rest for the bowel
Antibiotics into a vein start straight away. You stop eating, and fluids and sometimes nutrition are given through a drip while the join is given a chance to seal.
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Draining a collection
If the leak has formed a pocket of infected fluid, a radiologist can often place a thin drain through the skin under scan guidance, without another operation.
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A second operation, if needed
If the leak is large or you are very unwell, the surgeon goes back in to wash out the tummy and usually brings the bowel out as a stoma to take the join out of use. That stoma is often temporary.
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Side by side
A small contained leak and a large leak, compared
Small, contained leak
Large or free leak
Mild fever, local pain, found on a scan
Severe pain, very unwell, sometimes dangerously low blood pressure
Antibiotics, bowel rest and sometimes a drain through the skin
An urgent second operation, usually with a stoma
A longer hospital stay, usually days
Often a stay in intensive care and a much longer recovery
The join usually heals and no stoma is needed
A stoma for months, and any chemotherapy is delayed
Commonly believed
Four things families say about leaks, and what is true
"A leak means the surgeon made a mistake."
Leaks happen in careful hands too. Healing depends on the blood supply to the bowel ends, the tension on the join, and the person's own tissue, none of which the surgeon fully controls. What matters most is how quickly it is spotted and dealt with.
"We went home, so the danger is over."
Most leaks show in the first week, but some appear after discharge. Anyone who becomes feverish or develops new tummy pain in the first weeks at home should be seen the same day, however well they were when they left.
"If he has a leak, the cancer will spread."
A leak is an infection problem, not a cancer problem. It can delay chemotherapy, and your oncologist will factor that in, but the leak itself does not seed cancer into the tummy.
"A stoma after a leak is permanent."
Usually it is not. A stoma made to rescue a leak rests the join while it heals, and many are reversed once scans show the join has sealed and treatment is finished. Some are kept, and your surgeon will be straight with you about which is likely.
Being straight with you
What this page cannot tell you, and what to ask
This page cannot tell you whether your pain or fever is a leak. Fever after bowel surgery has several causes, including chest, urine and wound infections, and only examination, blood tests and usually a scan can separate them. Any of these signs in the first weeks earns a same-day check.
Who is at higher risk, and what is done about it
People with a join low in the pelvis, smokers, people with poorly controlled diabetes, people who are malnourished, and people who had radiotherapy before surgery are at higher risk. Surgeons respond by building people up before surgery, by making a protecting stoma at the first operation, and by watching more closely afterwards. Stopping smoking before surgery is the one thing in your own hands.
Questions worth asking before the operation
Ask how the surgeon plans to check the join is healthy at the end of the operation, whether a protecting stoma is likely and why, what the signs of a leak are, and whom to call at night if they appear. A surgeon who answers these plainly is one who has thought about it.
If you are already home and unsure, call the helpline. It is far better to be checked and sent home than to wait a night.Questions we are asked
Common questions about anastomotic leak
How soon after surgery does a leak show?
Most show within the first week, often between the third and seventh day, when the join is under most strain and the person is starting to eat. Some appear later, after going home. That is why fever or new tummy pain in the first few weeks always earns a same-day check.
How common is it?
It affects a minority of people after colectomy, and it is more common when the join is low in the pelvis than when it is higher up in the colon. Ask your surgeon what the risk is for your operation specifically. A figure for one kind of join says little about another.
Can a leak be treated without another operation?
Often, yes. A small contained leak is usually managed with antibiotics, bowel rest and sometimes a drain placed through the skin under scan guidance. A larger leak, or one making you very unwell, needs a second operation, usually with a stoma to rest the join.
Will I need a stoma if I have a leak?
If a second operation is needed, usually yes, so that nothing passes through the join while it heals. Many of these stomas are reversed months later once scans show the join has sealed. Your surgeon will tell you honestly whether reversal looks likely in your case.
Does a leak delay chemotherapy?
Usually, yes. Chemotherapy does not start until the infection has cleared and you are eating and recovering. Your oncologist weighs the delay against the benefit and adjusts the plan with you. Tell the oncology team about the leak early rather than assuming the original date is fixed.
What should the family watch for at home?
Temperature twice a day, pain that is getting worse rather than better, vomiting, a swollen tummy, and the person looking grey, confused or breathless. Any of these, or simply a strong feeling that something is wrong, is reason to call and come in the same day.
Could it have been prevented?
Sometimes the risk can be lowered, by stopping smoking, controlling diabetes, building up nutrition before surgery, and by the surgeon making a protecting stoma. It cannot be brought to nothing, because healing depends on the person's tissue. A leak is not proof of anyone's failure.
Is a leak dangerous?
It can be, which is why it is treated as an emergency. Caught early, most leaks are managed and the person recovers, though the stay is longer. Caught late, the infection can spread through the tummy and the bloodstream. Speed matters more than anything else, so never wait to see.
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Sources
- NHS — Colostomy
- Cancer Research UK — Bowel cancer treatment
- NICE — Colorectal cancer (NG151)
- American Cancer Society — Colorectal cancer surgery
- National Cancer Institute — Colon cancer treatment (PDQ)
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.
Keep reading
Related pages
What an Anastomosis IsThe join this page is aboutWill I Wake Up With a Stoma?Why a protecting stoma is sometimes madeComplications and Red FlagsEvery red flag after cancer surgery in one placeICU and the First Days After SurgeryWhat the checks in the first days are forBowel Obstruction After Colon SurgeryThe other cause of pain, swelling and vomiting
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Recently had bowel surgery and worried?
If there is fever, worsening pain or vomiting, go to a hospital today. For anything less urgent, call the helpline and a surgical oncologist will tell you whether it needs a same-day check. One helpline serves every CION centre.