Overview of gastroscopy and colonoscopy
Gastroscopy and colonoscopy are endoscopy tests in which a soft, flexible tube with a small video camera at its tip is passed into the digestive tract, through the mouth or through the back passage. This lets the doctor look directly at the lining, take tissue samples and treat some problems straight away, often during the same test.
Gastroscopy: a lit, flexible tube, thinner than your little finger, is passed through the mouth. It is used to examine the oesophagus (food pipe), the stomach and the duodenum (the first part of the small intestine).
Colonoscopy: the endoscope is gently passed through the back passage (anus). It is used to examine the rectum (the last 12 to 15 cm of the large bowel before the anus) and the whole of the large bowel (colon).
The two tests look at different parts of the digestive tract, but they follow the same principle, and the way you prepare for them, the sedation used and the recovery afterwards have a lot in common.
Who is it for?
A gastroscopy or colonoscopy is done when symptoms, a screening programme or a known condition make it useful to look directly at the lining of the digestive tract.
Gastroscopy
- to investigate abdominal pain, nausea, vomiting, difficulty swallowing or heartburn
- for bleeding from the upper digestive tract, to find where it is coming from and why
- to detect reflux, inflammation of the stomach lining (gastritis), ulcers or tumours in the oesophagus, stomach and duodenum; early-stage cancer can also be found this way
Tissue samples (biopsies) are taken from any suspicious areas with special instruments, so that a reliable diagnosis can be made. In suitable patients, the endoscope can also be used to widen narrowed areas, remove polyps and retrieve foreign objects left in the digestive tract. You can read more about the conditions a gastroscopy can detect on the stomach cancer surgery and reflux surgery pages.
Colonoscopy
- as a screening test for early detection of bowel cancer
- if you are known to have polyps, or to remove polyps (polypectomy)
- before and/or after an operation, such as bowel surgery
- to investigate blood in your stools or a change in bowel habits
- to monitor inflammatory bowel disease (ulcerative colitis, Crohn's disease)
Risks
Both tests are generally safe, but, as with any medical procedure, complications can occur.
Gastroscopy: you may have a sore throat and mild difficulty swallowing for a few hours afterwards. Rarely, there can be a reaction to the sedative. Very rarely, the test can cause bleeding, especially after a tissue sample or treatment, or a tear in the wall of the digestive tract.
Colonoscopy: colonoscopy with tissue sampling is a safe procedure. Very rarely, however, complications can occur:
- bleeding where tissue was taken or a polyp was removed; a blood transfusion is needed only very rarely
- a tear (perforation) in the bowel wall; in this case, emergency surgery may be needed to close the hole
- rarely, a reaction to the sedative
- occasionally, a reaction or swelling where the cannula (a thin tube in a vein) was put in
Taking a tissue sample does not cause cancer. Removing polyps from the large bowel, on the other hand, is important to help prevent bowel cancer later on.
Preparation
Good preparation is what makes gastroscopy and colonoscopy safe and reliable, and the steps differ for each one.
Gastroscopy
- Your stomach must be completely empty. Do not eat or drink anything for at least eight hours before the test.
- Tell your doctor about all the medicines you take and any known drug allergies. The dose may need to be adjusted.
- This applies especially to vitamin E, anti-inflammatory painkillers, blood-thinning medicines and insulin.
- If you have serious heart or lung disease, you will need special care.
Colonoscopy
- The rectum and large bowel must be completely clear of stools and residue. This is done with special bowel preparation solutions, or with cleansing fluids, laxatives and enemas taken over several days.
- If the bowel is not completely clean, the test is not reliable or may not be possible at all. If you are having trouble with the bowel preparation, please contact your doctor.
- You can usually keep taking your regular medicines. However, tell your doctor if you take vitamin E, painkillers, blood-thinning medicines or insulin.
What happens
Before the procedure
Both tests are usually done under sedation, with medicine that makes you calm and drowsy. It slows your reflexes for the rest of the day. So please do not come alone, do not drive or operate machinery that day, and avoid tasks that need concentration.
On the day
Gastroscopy: a spray numbs your throat and makes it easier to pass the tube. You lie on your side or back, and the endoscope is passed through your mouth into the oesophagus. The stomach is gently filled with air so that it can be seen more clearly. Under sedation, most patients fall asleep during the test; only a few find it uncomfortable.
Colonoscopy: you lie on your side or back. The test is usually well tolerated, but you may feel pressure and bloating in your abdomen, and cramping pain. It takes between 15 and 60 minutes. In rare cases, the whole of the large bowel cannot be seen; another imaging test of the large bowel will then be planned.
If an area needs a closer look, a tissue sample is taken and examined under the microscope (pathology). Polyps are usually removed, either with an electric current or with a fine wire loop. Unless your doctor tells you otherwise, polyps are usually benign (not cancer).
After the procedure
Gastroscopy: you rest for one to two hours until the sedative wears off. You may have a sore throat and mild difficulty swallowing for a few hours. Unless you have been told otherwise, you can eat as normal and carry on taking your medicines.
Colonoscopy: mild cramping pain and a bloated abdomen from the air used during the test are normal. They go away once the air has been passed.
You will be told the result straight after the test or at your next follow-up appointment. If tissue samples were taken, their results come later, once they have been examined under the microscope.
Aftercare
If polyps were found during your colonoscopy, the test may need to be repeated. Your doctor will explain how often you should have a colonoscopy, because the interval depends on what was found.
Please contact your doctor straight away if you have severe abdominal pain, fever, shivering (chills) or heavier bleeding from the back passage after a colonoscopy. After a gastroscopy, contact your doctor straight away if you have severe pain in the chest or abdomen, a fever, vomiting blood or black, tarry stools.