Colonoscopy and endoscopy: preparation, sedation and what to expect

Endoscopy is a way of looking inside the digestive tract using a thin, flexible tube with a camera at its tip. Being invited for a colonoscopy or a gastroscopy can feel daunting, mainly because of the preparation and uncertainty about sedation. Knowing what to expect makes the day much easier. This guide covers the three tests people most often ask about: gastroscopy, colonoscopy and capsule endoscopy.

Which test is which?

Test	What it looks at	How it is done
Gastroscopy (upper endoscopy)	Oesophagus, stomach and duodenum	Endoscope passed through the mouth
Colonoscopy	Rectum and large bowel (colon)	Colonoscope passed through the bottom
Capsule endoscopy	Mainly the small intestine	A camera capsule is swallowed and sends images to a recorder

During a gastroscopy or colonoscopy, the doctor can take small tissue samples (biopsies), remove polyps or treat bleeding. A capsule endoscopy only records images, but it can show parts of the digestive tract that the other two tests cannot reach.

Before any endoscopy: medicines and health information

Whatever test you are having, tell your care team about your health conditions and all medicines, vitamins and supplements you take. It is especially important to mention blood thinners, aspirin, anti-inflammatory painkillers, diabetes medicines and iron. Some of these may need adjusting for a short time, and iron can darken the stool and make the bowel lining harder to see. Do not stop any prescribed medicine unless your team tells you to. Let them know if you are or might be pregnant, and bring a list of your medicines on the day.

Preparing for a gastroscopy

For a gastroscopy, the stomach needs to be empty. You will usually be asked not to eat or drink for a number of hours beforehand; follow the timings in your appointment letter. Plan for someone to take you home if you choose sedation.

On the day, you may be given a throat spray or a liquid to gargle, which numbs the throat and reduces gagging. Many people also have a sedative through a cannula, although some prefer to have the test without it. You will usually lie on your side while the doctor passes the endoscope through your mouth into the oesophagus, stomach and duodenum. The procedure itself is usually short, but the whole visit takes longer because of preparation and recovery.

Preparing for a colonoscopy

A colonoscopy needs more preparation, because the large bowel must be completely empty for the doctor to see the lining clearly.

Diet in the days before

You may be asked to avoid high-fibre foods for several days and then follow a clear-liquid diet for a day or more. Clear liquids typically include water, clear broth, clear juices and jelly. Drinking plenty of these helps prevent dehydration.

Bowel preparation

The bowel preparation is a laxative, usually a drink, taken according to a set timetable, often the evening before and the morning of the test. Diarrhoea can begin a few hours after you start taking it, so stay close to a toilet. It is important to finish the preparation; if side effects stop you, call your care team rather than giving up, because an incomplete preparation can mean the test needs repeating.

Practical tips

• Plan to be at home for the evening of your preparation.
• Use soft toilet tissue and a barrier cream if your skin becomes sore.
• Arrange for someone to collect you and stay with you after sedation.
• Wear loose, comfortable clothing on the day.

Sedation and comfort

An endoscopy may be uncomfortable but should not be painful. Hospitals offer different options, so ask what is available:

• Sedation given through a cannula, which makes you relaxed and drowsy; you may be awake but not remember much afterwards.
• Painkillers given through the cannula.
• Gas and air, which you breathe in during the procedure and which wears off quickly.
• Local anaesthetic throat spray for a gastroscopy.

If you have sedation, you cannot drive for 24 hours. You will need someone to take you home and ideally stay with you for the rest of the day and overnight. During this time, also avoid alcohol, operating machinery and making important decisions.

What happens during a colonoscopy

You will change into a gown and usually lie on your left side. The doctor gently passes the colonoscope through your bottom and guides it around the large bowel. Air, carbon dioxide or water is used to open the bowel so the lining can be seen, which can cause some cramping. The doctor examines the lining carefully, especially while slowly withdrawing the scope. Polyps can be removed and biopsies taken during the test, and you will not feel this. The test itself usually takes less than an hour, though you may be at the unit for a couple of hours in total.

Capsule endoscopy: what to expect

For a capsule endoscopy, you swallow a capsule about the size of a large vitamin pill. It contains a tiny camera, a light, a battery and a transmitter, and it sends images to a recorder worn on your waist or shoulder.

• Preparation: you may need a bowel-clearing medicine, clear liquids for a period and a time without food or drink before swallowing the capsule. Avoid smoking beforehand.
• During the day: most normal activities are fine, but avoid heavy lifting and strenuous exercise. Your team will tell you when you can eat and drink again.
• Afterwards: the capsule usually passes naturally in a bowel movement, often within a day, and is flushed away. If you have not seen it pass within two weeks, tell your provider, as an X-ray may be needed.
• Important: avoid MRI scans and strong magnetic fields until the capsule has passed.

Problems are very rare. The main risk is the capsule getting stuck where the bowel is narrowed, which occasionally needs treatment to remove it. Tell your team beforehand if you have had a bowel blockage, abdominal surgery, swallowing problems or have an implanted device such as a pacemaker.

After the test and warning signs

You will rest in a recovery area until any sedation wears off. Bloating, wind and mild cramping are common for a short time, and after a gastroscopy your throat may feel sore. After a polyp removal or biopsy, a little blood in your stool for a day or two is common. Many people return to their normal diet and activities the next day.

Complications are uncommon. They include bleeding, a tear (perforation) in the bowel or upper digestive tract, and reactions to sedation. Bleeding and perforation are more likely when polyps are removed, and bleeding can occasionally occur up to around two weeks later. Seek urgent medical care or contact emergency services if you have severe or worsening abdominal or chest pain, fever, heavy bleeding or bleeding that does not settle, vomiting (especially blood or material like coffee grounds), black stools, dizziness or weakness, or difficulty breathing.

Results and planning your visit

Before you leave, the doctor or nurse may explain what was seen, often once the sedation has worn off. If biopsies were taken or polyps removed, these are examined in a laboratory, and results can take from several days to a few weeks. Ask how and when you will receive them, and whether a follow-up appointment is needed.

If you are travelling for your test, a few practical points can make the visit smoother:

• Bring a written list of your medicines and any previous endoscopy or scan reports.
• Make sure the person accompanying you can stay for the rest of the day if you have sedation.
• Allow time in your plans for the bowel preparation the day before a colonoscopy.
• Ask for copies of your report and any laboratory results to share with your own doctor at home.

Next steps

If you have been advised to have a colonoscopy or an endoscopy, or you would like to discuss screening, a gastroenterologist can explain which test suits you and how to prepare. Read more about our gastroenterology care, use Find my physician to be matched with a specialist, or see what is included in our cancer screening package.