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CION Cancer Clinics
Bowel preparation before a colectomy, step by step | CION Cancer Clinics
Bowel preparation means emptying the large bowel before the operation, usually by drinking a laxative solution the day before, sometimes with antibiotic tablets as well. Not everyone having a colectomy needs it, and your surgeon decides which kind you get. This page explains why it is done, how the day typically goes, what to have ready at home, who it is not safe for, and the signs that mean you should stop and call the ward. 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
- What is bowel preparation, and will I need it?
- How does the day before surgery usually go?
- Which kind of preparation might you be given?
- What to have ready at home on prep day
- Four things families get wrong about bowel prep
- Who is bowel prep not safe for, and what this page cannot tell you
- Common questions about bowel prep before colectomy
The short answer
What is bowel preparation, and will I need it?
Bowel preparation, or bowel prep, means emptying the large bowel before the operation, usually by drinking a strong laxative solution the day before. Not everyone having a colectomy needs it. Your surgeon decides, and the choice depends on which part of the bowel is being removed and how your centre works.
Why it is done
An empty bowel is lighter, easier to handle through small cuts, and easier to join. Some teams also give antibiotic tablets alongside the laxative, because clearing stool and reducing the germs in the bowel together lowers the chance of a wound or join infection. That combination is now the approach many centres prefer for planned colon surgery.
Why practice varies
For years the evidence went back and forth, and surgeons still differ. Operations on the right side of the colon often need less preparation than operations on the left or near the rectum. Emergency operations usually get none at all, because there is no time and the bowel is blocked. If the person in the next bed had a different routine, that is why. Follow the instructions written for you, not a general guide.
This page describes what bowel prep typically involves. Your own written instructions from your surgical team come first wherever the two differ.Typically
How does the day before surgery usually go?
Light food, then liquids only
Most teams ask for low-fibre meals in the run-up, then clear liquids only on prep day: water, clear soup, coconut water, weak tea without milk. Nothing red or purple, which can be mistaken for blood inside the bowel.
The laxative drink
A powder mixed into a large volume of water, drunk over a few hours, often in two halves. It tastes salty. Chilling it, using a straw and sucking a lemon wedge between glasses all help.
Stay near a toilet
The effect starts within an hour or two and continues for several hours. Motions become watery and eventually clear or pale yellow, which is the sign it has worked.
Antibiotic tablets, if prescribed
Some teams add a short course of antibiotic tablets on prep day. Take them exactly as written on your sheet. They are timed around the laxative, and the timing matters.
Fasting before the anaesthetic
Your anaesthetist sets the time after which nothing may be eaten, and the time after which nothing may be drunk. These are separate rules and are written on your admission sheet.
Not sure whether this applies to you?
Ask an oncologistYour team chooses
Which kind of preparation might you be given?
Four patterns cover most planned colectomies. Which one you get is a surgical decision, not a sign of how serious things are.
Full laxative prep
The whole bowel is emptied with a laxative solution such as polyethylene glycol, the same type used before a colonoscopy.
Often used for
- Left-sided and sigmoid operations
- Operations where a temporary stoma is planned
Laxative plus antibiotic tablets
Full prep with oral antibiotics added on the same day. The combination is supported by the strongest evidence for lowering infection after planned colon surgery.
The antibiotics are tablets you swallow, separate from the injection you receive in theatre.Enema only
A small enema on the morning of surgery to clear the last part of the bowel, without emptying the whole of it.
Often used for
- Some right-sided operations
- Patients who cannot tolerate a full prep
No preparation
Some surgeons operate on the right colon with no prep at all, and emergencies almost never have one. The operation is planned around it.
Practical
What to have ready at home on prep day
- A toilet you can reach quickly, with the door unlocked and the light on
- Plenty of clear fluids chilled in the fridge, including something with salt and sugar
- Soft toilet paper or wet wipes, and a barrier cream for sore skin
- Your written instruction sheet and the ward phone number within reach
- Someone at home with you, especially if you are elderly or live alone
- Your regular medicines laid out, taken only as your team has told you
- Loose clothes and a bag already packed for admission
- A charged phone, because you will be sitting near the toilet for hours
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
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When to stop and call the ward the same day
If you vomit the solution up repeatedly and cannot keep fluids down, if you feel faint or your heart is racing, if the belly becomes painful and swollen with nothing passing, or if you are diabetic and your sugar drops low, stop drinking the prep and call the number on your sheet straight away. A swollen, painful belly on prep can mean the bowel is blocked, and the prep must not be forced through it. Do not wait until the morning of admission to mention it.
Commonly believed
Four things families get wrong about bowel prep
"Drinking extra prep will make the bowel cleaner and the surgery safer."
More is not better. The solution is dosed to empty the bowel while keeping your salts and fluid balance safe. Taking extra, or repeating it, can dehydrate you and disturb your salts, which is a risk under anaesthetic. Take what is written and no more.
"My bowels are regular, so I can skip it."
Regular motions still leave the bowel full. The prep is about the bowel being empty and light on the table, not about constipation. If it has been prescribed, the surgeon is planning the operation around an empty bowel, and skipping it can mean postponing the surgery.
"Prep day means no water either."
The opposite. On prep day you are losing a great deal of fluid, and you should keep drinking clear liquids until the time your anaesthetist has set. Arriving dehydrated makes the anaesthetic harder and the veins harder to find.
"I should stop all my tablets on prep day to be safe."
Never decide this yourself. Some medicines are continued, some are paused, and the timing is set by your surgeon, anaesthetist and prescribing doctor. Blood thinners, diabetes medicines and blood pressure tablets each have their own instructions. If your sheet is silent on a medicine, ask before prep day.
Being straight with you
Who is bowel prep not safe for, and what this page cannot tell you
A full laxative prep is not given when the bowel is blocked or nearly blocked, because forcing fluid against a blockage can make things worse. It is used cautiously, or not at all, in people with kidney disease, heart failure, or a frail elderly person who cannot manage the volume. That is one reason two people with the same operation get different instructions.
If you have diabetes
A day on clear fluids changes what your sugar does, and the insulin or tablets you normally take may need adjusting for that day. This must be planned with your team in advance. Tell them you are diabetic when the prep is prescribed, not on the day. See the medicines around surgery page.
What this page cannot tell you
It cannot tell you which prep you will have, when to take it, how much to drink, or what to do with your own medicines. Those instructions come only from your surgical team in writing. If you have not received a written sheet, ask for one before you leave the clinic. The days before your operation guide covers the rest of that week.
If you cannot read your instruction sheet, or it is in a language you are not comfortable with, call the helpline and someone will go through it with you in Telugu.Questions we are asked
Common questions about bowel prep before colectomy
How do I know the prep has worked?
The motions become watery and then clear or pale yellow, with no solid pieces. If they are still brown and cloudy after you have finished the solution, tell the ward when you arrive. Do not take extra on your own.
Can I eat anything on prep day?
Usually only clear liquids: water, clear soup or rasam without solids, coconut water, weak tea without milk, and clear fruit juice without pulp. No milk, no solids, and nothing red or purple. Your sheet will say exactly what is allowed.
What if I cannot finish the drink?
Take a break, chill it, use a straw, and try again slowly. If you vomit it up more than once or feel faint, stop and call the ward. Do not force it. The team can arrange an alternative.
Should I stop my blood thinner or diabetes tablets?
Only as your surgeon, anaesthetist or prescribing doctor has told you, and only at the time they set. Never stop or change a medicine on your own for surgery. If your instruction sheet does not mention a medicine you take, ring and ask before prep day rather than guessing.
Will the prep hurt or make me ill?
Expect bloating, cramping, some nausea and a sore bottom from the frequent motions. Those are normal. Severe belly pain, a swollen tight belly, repeated vomiting or feeling faint are not, and are the reason to stop and call.
Do I need prep for a right hemicolectomy?
Sometimes not. Many surgeons operate on the right colon with an enema only or no preparation at all, because the stool there is liquid and the join is easier. Others still prefer a full prep. Follow your own sheet.
Why am I getting antibiotic tablets as well?
Because the laxative empties the bowel but does not reduce the germs living in it. Antibiotic tablets taken on prep day do that, and the two together lower the chance of a wound or join infection after surgery.
Can I do the prep at home, or should I be admitted?
Many people do it at home the day before and come in on the morning of surgery. If you are elderly, live far from the hospital, have kidney or heart problems, or are diabetic, your team may admit you a day early so the prep is done with nurses on hand.
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Sources
- Cancer Research UK — Surgery for bowel cancer
- NICE — Colorectal cancer (NG151)
- American Cancer Society — Surgery for Colon Cancer
- NHS — Bowel cancer - Treatment
- Macmillan Cancer Support — Bowel cancer
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
The Days Before Your OperationEverything else that happens in the week before admissionMedicines Around Cancer SurgeryHow blood thinners and diabetes medicines are handled, and by whomColectomy: What the Operation InvolvesWhat the prep is preparing you forAnaesthesia for Cancer SurgeryWhy the fasting rules are separate from the prepEmergency Colectomy for Obstruction or PerforationWhy a blocked bowel gets no prep at all
Talk to us
Not sure what your prep instructions mean?
Call the helpline with your instruction sheet in front of you and a nurse will go through it with you, in Telugu if you prefer. One helpline serves every CION centre.