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CION Cancer Clinics
Diarrhoea after gastrectomy: why it happens and what helps | CION Cancer Clinics
Loose motions after a gastrectomy are common in the first few months and usually have a cause that can be found. The stomach used to hold food back and release it slowly. Without it, food and bile reach the small bowel fast, and the nerves that once set the pace of the gut may have been cut. This page explains the usual causes, which ones settle on their own, and the signs that need a call the same day. 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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On this page
- Why do I have loose motions after my stomach was removed?
- Which of these is causing yours?
- What to do this week, before your next appointment
- Words you may see, in plain language
- Four things families tell us, and what is actually true
- What this page cannot tell you
- Common questions about loose motions after gastrectomy
The short answer
Why do I have loose motions after my stomach was removed?
Loose motions after a gastrectomy happen because the stomach used to hold food back and release it slowly, and now nothing does. Food, fluid and bile reach the small bowel much faster than the bowel is used to, and it responds by pushing everything through quickly.
The stomach did more than you think
Before the operation, a meal sat in the stomach, was mixed with acid, and then trickled into the small bowel a little at a time. Once the stomach is gone, or most of it is gone, a meal arrives in the bowel almost at once. Sugary drinks and large meals are the worst for this, because they pull water into the bowel and the bowel empties itself in a hurry.
Nerves were cut too
The vagus nerves run along the stomach and help set the pace of the gut. Removing the stomach usually means cutting them. For some people the bowel then runs faster for months, sometimes with a sudden urge that is hard to hold. It is a known effect of the surgery and usually eases as the months pass.
Loose motions on their own are not a sign that the cancer has come back. That fear is very common and almost always unfounded.Finding the cause
Which of these is causing yours?
Five causes account for nearly all loose motions after a gastrectomy. The pattern, and when it happens, usually points to one.
Dumping
Food rushing into the bowel too fast. Loose motions come soon after eating, often with cramps, a racing heart, sweating or feeling faint. Sweet foods and drinks set it off most.
Cut vagus nerves
The gut runs faster with less control. Motions can be sudden and urgent, at any time of day, and are not tied to what was eaten. This one tends to improve on its own as the months pass.
Bile and fat
Bile now meets food later and in a different order. Fat may not be broken down well, so motions can be pale, greasy, hard to flush and very smelly. Weight loss often comes with it.
Bacteria overgrowing in the small bowel
Without stomach acid, bacteria that were once killed off can grow in the small bowel. Bloating, wind and loose motions that drag on for weeks are the usual pattern. It is treated with tablets from your doctor.
Infection or medicines
A stomach bug behaves the same as it would in anyone else. Iron tablets, some antibiotics and certain supplements also loosen the bowel. Tell your team every medicine you take.
Not sure whether this applies to you?
Ask an oncologist
!
When loose motions cannot wait
Go to the nearest emergency department the same day, and say the person has had a gastrectomy, if there is blood or black tar in the motions, if they cannot keep any fluid down, if they are passing very little urine, or if there is fever with loose motions in the first weeks after surgery. Dehydration comes on fast without a stomach, and in the early weeks a fever can mean a leak at the join inside.
At home
What to do this week, before your next appointment
Replace fluid, but not with sweet drinks
Sip water, buttermilk, thin dal water or an oral rehydration mix through the day. Avoid juice, cold drinks and sweet tea. They make dumping worse and pull more water into the bowel.
Separate drinking from eating
Drink between meals rather than with them. Fluid taken with food pushes the meal through faster.
Eat small, plain and often
Small plates several times a day, with protein at each one. Curd rice, soft idli, boiled egg, well-cooked dal and soft vegetables sit better than fried, sweet or very spicy food while the bowel is unsettled.
Keep a simple diary
Note what was eaten, when the motion came, and what it looked like. Two or three days of this tells your surgeon more than any amount of description from memory.
Ask before you take anything
Loperamide, enzyme capsules and antibiotics each suit a different cause. Taking one for the wrong cause delays the right answer. Call your team and describe the pattern first.
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On your report
Words you may see, in plain language
- Post-vagotomy diarrhoea
- Loose motions caused by the vagus nerves being cut during the operation. It is a known effect of the surgery and tends to ease with time.
- Dumping syndrome
- A group of symptoms, including loose motions, that come from food reaching the bowel too fast. Managed mostly by changing how and what you eat.
- Steatorrhoea
- Fat passing out in the motions instead of being absorbed. The motions look pale, oily and float. Enzyme capsules taken with food may be suggested.
- Bile acid diarrhoea
- Bile reaching the large bowel and irritating it. Your doctor may suggest a medicine that binds the bile.
- SIBO
- Small intestinal bacterial overgrowth. Too many bacteria in the small bowel, now that there is no acid to keep them down. Usually treated with a course of tablets.
Commonly believed
Four things families tell us, and what is actually true
"Loose motions mean the cancer has spread to the bowel."
Almost never. Loose motions after a gastrectomy are a result of the operation itself, and they are expected. If something needs checking, your surgeon will arrange it. Do not carry this fear alone for weeks; ask at the next visit.
"He should stop eating until it settles."
Stopping food makes things worse, not better. Without a stomach, weight falls quickly, and a person who is losing weight recovers more slowly from everything. Keep eating small plain meals. Change what is eaten, not whether.
"Glucose water will bring her strength back."
Sugary drinks are the single most common trigger for dumping and for loose motions after this operation. Buttermilk, thin dal water or an oral rehydration mix are far kinder to the bowel and replace what has been lost.
"A loperamide tablet from the chemist will fix it."
It may quieten the bowel for a day. But if the cause is bacterial overgrowth or fat not being absorbed, it hides the problem without treating it. Ask your team before taking it, and tell them if you already have.
Being straight with you
What this page cannot tell you
This page cannot tell you which cause is yours. The patterns above overlap, and two causes often run together in the same person. A proper answer comes from your surgeon or dietitian hearing the pattern, looking at your weight and blood tests, and sometimes sending a stool sample.
Who this page does not fit
If you are still in hospital, or went home only a few days ago, do not use this page to decide what is happening. In the first two weeks after surgery, loose motions with fever, pain or vomiting are treated as a possible leak until proved otherwise, and that is a hospital matter. This page is written for the weeks and months after that.
What to bring to the appointment
Bring the diary, a list of every tablet and supplement, and your most recent weight. Say how many motions a day, whether they wake you at night, and whether they float or look oily. Those few details are what the surgeon will ask first.
If you are between appointments and unsure whether to wait, call the helpline. Someone will talk it through with you.Questions we are asked
Common questions about loose motions after gastrectomy
How long will the loose motions last?
For most people the bowel settles over the first few months as it learns to cope without a stomach. For some it takes longer, and a few need a cause found and treated before it improves. If it is not easing by your follow-up visits, say so plainly.
Is it dumping or something else?
Dumping is tied to meals. It comes soon after eating, often with cramps, sweating, a racing heart or feeling faint, and sweet food sets it off. Loose motions at any time of day, or that look pale and oily, or that drag on with bloating, point to one of the other causes.
What should I eat and drink today?
Small plain meals with some protein in each: curd rice, soft idli, boiled egg, well-cooked dal. Drink water, buttermilk or an oral rehydration mix between meals rather than with them. Leave out juice, cold drinks, sweets, fried food and very spicy food until the bowel is calmer.
Can I take loperamide or another anti-motion tablet?
Only after asking your surgeon or the helpline. It helps some causes and is unhelpful for others, and in the early weeks after surgery it can hide a problem that needs attention. Enzyme capsules and antibiotics are used for other causes, so the pattern needs to be heard first.
Why are my motions pale and greasy?
Because fat is passing through without being absorbed. After a gastrectomy, bile and the digestive juices meet food later and in a different order, so fat is not broken down as well. Tell your team. Enzyme capsules taken with meals often help.
I am losing weight along with the loose motions. Is that serious?
It needs attention, not panic. Some weight loss is expected after this operation, but steady loss along with loose motions suggests food is not being absorbed properly. That is usually treatable once the cause is found. Bring your weights to the next visit and ask to see the dietitian.
Does it mean the join inside has leaked?
In the first couple of weeks after surgery, loose motions with fever, pain, vomiting or feeling very unwell are treated as a possible leak until proved otherwise, and you should be seen the same day. Months later, loose motions on their own are very unlikely to be a leak.
Will the diarrhoea come back every time I eat sweets?
Sweet foods and drinks are the most reliable trigger, and for many people they stay a trigger for a long time. A small piece of sweet at the end of a proper meal is usually tolerated far better than a sweet drink on an empty stomach.
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Sources
- Cancer Research UK — Living with stomach cancer
- Macmillan Cancer Support — Stomach cancer
- American Cancer Society — Surgery for stomach cancer
- NHS — Diarrhoea and vomiting
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
Dumping Syndrome After GastrectomyThe most common cause of loose motions after this operationManaging Dumping Syndrome With DietThe food changes that calm the bowelBile Reflux After GastrectomyBile going the other way, and how it is handledStopping Weight Loss After Stomach SurgeryWhen loose motions are costing you weightComplications and Red FlagsThe signs after any cancer surgery that need same-day care
Talk to us
Loose motions that are not settling?
Tell us when the operation was and what the pattern looks like. A surgical oncologist or dietitian will call you back and help you work out the cause. One helpline serves every CION centre.