Glossary — Coloscopy.com

In short

This glossary defines the medical terms used elsewhere on Coloscopy.com in plain language. Definitions are short — usually one to four sentences — and aim to explain what a term means in the context of bowel care, not to cover every nuance. When a word is used differently by different specialties, the entry notes that.

What this page covers

An alphabetised list of terms a reader is likely to encounter on a referral letter, a prep instruction sheet, a pathology report, or a discharge summary related to coloscopy. Cross-links point to longer pages where the topic deserves more space.

How to use this list

Use your browser's find function (Ctrl-F or Cmd-F) to jump to a term. Definitions assume the reader has no medical background; they are not exhaustive references. If a definition contradicts something your clinician has told you about your own care, follow your clinician.

A

Adenoma: A type of polyp made of abnormal glandular tissue. Adenomas are not cancer, but a small fraction will, if left in place over years, develop into colorectal cancer; this is why the polyps are removed during a coloscopy. See polyp types in plain English.
Adenomatous polyp: Another way of writing adenoma. The two terms are interchangeable on most pathology reports.
AGA: The American Gastroenterological Association, a professional society of gastroenterologists in the United States that issues clinical guidelines and position statements.
Anaesthesia: Medication given to remove sensation, awareness, or both. For coloscopy, true general anaesthesia is uncommon; what is more often used is intravenous sedation, sometimes deep, sometimes light. See sedation options.
Antispasmodic: A medication that relaxes the muscle of the bowel wall to reduce cramping during the test. Hyoscine butylbromide (Buscopan) and glucagon are the two most often used.
Appendix: A small finger-shaped pouch attached to the caecum. The opening of the appendix is sometimes seen during coloscopy and is used by the endoscopist as a landmark confirming that the scope has reached the start of the colon.
Ascending colon: The first part of the large bowel after the caecum, running upwards on the right side of the abdomen. See anatomy of the colon.
ASGE: The American Society for Gastrointestinal Endoscopy, the professional society for endoscopists in the United States. It publishes guidelines on technique, sedation, quality measures, and surveillance intervals.
Aspiration: The unintended entry of stomach contents, saliva, or fluid into the airway and lungs. It is the principal reason that solid food is held before sedation.
Benzodiazepine: A class of sedative drug. Midazolam is the benzodiazepine most often used for conscious sedation during coloscopy.
Biopsy: The taking of a small sample of tissue for examination under a microscope. During coloscopy, biopsies are taken with small forceps passed through the working channel of the scope. They are not painful.
Biopsy forceps: A small grasping instrument at the end of a long flexible cable, used to take tissue samples through the scope.
Bowel preparation: The process of cleaning the colon before the test, usually by drinking a laxative solution and following a clear-liquid diet for the day before. Often shortened to prep. See preparation overall.
BSG: The British Society of Gastroenterology, the United Kingdom's professional society for gastroenterologists. It publishes guidance for endoscopy services in the UK.
Caecum: The pouch where the small bowel joins the large bowel. It sits in the right lower abdomen and is the deepest point a coloscopy needs to reach for the test to be considered complete.
Caecal intubation: Reaching the caecum with the scope. Endoscopy units track the rate at which their endoscopists achieve this, as a quality measure.
CAG: The Canadian Association of Gastroenterology, the professional society for gastroenterologists in Canada.
Carbon dioxide insufflation: The use of carbon dioxide gas (instead of room air) to gently distend the bowel during the test. Carbon dioxide is absorbed across the bowel wall within minutes, which means much less bloating afterwards. Most modern units use it as standard.
Chromoendoscopy: A technique in which a dye (such as indigo carmine or methylene blue) is sprayed onto the bowel lining during the test to make subtle abnormalities easier to see. Used particularly for surveillance in long-standing inflammatory bowel disease.
Clear liquid: Any liquid you can see through that is free of pulp, dairy, and red or purple dye. Water, apple juice, white grape juice, clear broth, and most sports drinks count. Milk, orange juice, and tomato juice do not. See clear liquids, defined precisely.
Coloscopy / colonoscopy: The same examination of the large bowel using a flexible endoscope passed via the rectum. Coloscopy is more common in European medical traditions; colonoscopy is more common in the United States. This site uses coloscopy throughout and treats the two as interchangeable.
Conscious sedation: Also called moderate sedation. A state in which the patient is relaxed and comfortable but still able to respond to spoken instructions, usually achieved with a benzodiazepine (such as midazolam) plus an opioid (such as fentanyl).
Crohn's disease: A form of inflammatory bowel disease that can affect any part of the digestive tract, often in patches, and that involves the full thickness of the bowel wall. See inflammatory bowel disease.
Descending colon: The portion of the large bowel running downwards on the left side of the abdomen, between the splenic flexure and the sigmoid colon.
Diverticulum (plural: diverticula): A small outpouching of the bowel wall through a weak point. They are very common with age and almost always cause no symptoms.
Diverticulosis: The presence of diverticula in the colon. It is a description, not a disease, and is found incidentally in many adults having coloscopy. See diverticulosis.
Diverticulitis: Inflammation or infection of one or more diverticula. Unlike diverticulosis, this is an active condition that often causes pain, fever, and changes in bowel habit.
Dysplasia: Disordered, abnormal-looking cells. Pathologists describe dysplasia as low-grade or high-grade. Dysplasia is not cancer, but it is a step along the pathway some lesions follow towards cancer, and its presence in a polyp or in inflamed bowel changes follow-up.
EMR (endoscopic mucosal resection): A technique for removing a flat or sessile polyp by injecting fluid underneath it to lift it away from the deeper bowel wall, then cutting it off. Used for polyps too flat or too large to be safely snared in one piece.
Endoscope: The flexible tube with a camera and light at its tip used to examine the inside of the bowel. The colonoscope is one type of endoscope.
ESD (endoscopic submucosal dissection): A more advanced technique in which a large or difficult polyp is removed in a single piece by carefully dissecting it from beneath. ESD is offered in specialist centres and is used selectively.
ESGE: The European Society of Gastrointestinal Endoscopy, the European professional society for endoscopists.
FIT (faecal immunochemical test): A stool test that detects small amounts of human haemoglobin — that is, blood — in the stool. It is the screening test of choice in many national programmes. A positive result usually leads to a coloscopy.
FIT-DNA: A stool test that combines a FIT with markers of altered DNA shed by colorectal tumours and large polyps. Marketed in the United States under the name Cologuard.
Flexible sigmoidoscopy: An examination of the rectum and the sigmoid (and sometimes the descending) colon only, using a shorter scope. It does not look at the right side of the bowel and so is not equivalent to a coloscopy.
Fragmentation: A description on a pathology report indicating that a polyp was removed in pieces rather than in one piece. It is sometimes a limitation of how completely the lesion can be assessed at the margins.
GLP-1 receptor agonist: A class of medications that mimic the gut hormone GLP-1, used for diabetes and weight management. Examples include semaglutide and tirzepatide. They slow stomach emptying, which is relevant before sedation. See GLP-1 medications.
HAS: The Haute Autorité de Santé, the French national health authority, which publishes clinical recommendations including for cancer screening.
Haemorrhoid: A swollen vein in or around the anus or lower rectum. Internal haemorrhoids are very commonly noted on coloscopy reports. See internal haemorrhoids on the report.
Hepatic flexure: The bend in the colon under the liver, where the ascending colon turns to become the transverse colon. One of two natural sharp turns the scope must round.
Hyperplastic polyp: A common, benign polyp, particularly in the rectum and sigmoid. Most small hyperplastic polyps in the lower bowel are not considered to carry significant cancer risk.
IBD (inflammatory bowel disease): An umbrella term for chronic inflammatory conditions of the bowel, principally Crohn's disease and ulcerative colitis.
Ileocaecal valve: The one-way valve where the small bowel (ileum) empties into the large bowel (caecum). The endoscopist looks for it as a landmark confirming a complete examination.
Ileum: The last section of the small bowel, joining the colon at the ileocaecal valve. The endoscopist may pass the scope a short distance into the ileum (terminal ileum intubation) when investigating possible Crohn's disease.
Indication: The clinical reason for the test. Common indications for coloscopy include screening, surveillance after polyps, change in bowel habit, rectal bleeding, iron-deficiency anaemia, and follow-up of an abnormal stool test. Indication often determines how the procedure is billed and coded.
Insufflation: The introduction of gas into the bowel during the test to open the lumen so the wall can be seen. Carbon dioxide is preferred over room air because it is absorbed quickly afterwards.
Lynch syndrome: An inherited condition that increases the lifetime risk of colorectal cancer and several other cancers, caused by changes in DNA mismatch repair genes. People with Lynch syndrome start screening earlier and have it more often. See family history and genetics.
Margin: On a pathology report, the edge of the tissue that was removed. A negative or clear margin means abnormal cells were not seen at the cut edge; a positive or involved margin means they were, raising the question of whether anything was left behind.
MoviPrep: A brand of polyethylene-glycol-based bowel preparation taken as two litres of solution plus additional clear fluid. See PEG-based preparations.
NICE: The National Institute for Health and Care Excellence, England's body for clinical guidance. NICE produces guidance used by the National Health Service across many areas, including bowel cancer screening and surveillance.
Pedunculated: A polyp shaped like a mushroom, with a stalk attaching it to the bowel wall. Pedunculated polyps are usually straightforward to remove with a snare around the stalk.
PEG (polyethylene glycol): A large, non-absorbed molecule used in many bowel preparations. It draws water into the bowel without significant electrolyte shift, which is why PEG-based preps are usually preferred in patients with kidney or heart disease.
Perforation: A hole through the wall of the bowel. Perforation is a serious but rare complication of coloscopy, more common after polyp removal than after diagnostic-only examinations.
Polyp: A small growth on the lining of the bowel. Most polyps are not cancer; some types, given enough time, can become cancer, which is the basis for removing them when they are found.
Polypectomy: The removal of a polyp, performed during the same coloscopy in which the polyp is found.
Propofol: A short-acting intravenous anaesthetic that produces deep sedation reliably. It is administered by an anaesthesia clinician. See sedation options.
RACGP: The Royal Australian College of General Practitioners, which publishes preventive-care guidelines used in Australian primary care.
RCoA: The Royal College of Anaesthetists, the United Kingdom's professional body for anaesthetists, which publishes standards including those for sedation outside the operating theatre.
Rectum: The final straight section of the large bowel, ending at the anus. The rectum is examined first as the scope is inserted and again, often with the scope turned back on itself (retroflexion), at the end of the test.
Sessile: A polyp that sits flat against the bowel wall without a stalk. Sessile polyps are removed differently from pedunculated polyps, sometimes with EMR.
Sessile serrated lesion: A flat polyp, usually in the right colon, with a particular microscopic appearance. Sessile serrated lesions are now recognised to carry an increased risk of progressing to cancer and are tracked more carefully than they used to be. Older reports may call them sessile serrated adenomas or sessile serrated polyps.
Sigmoid colon: The S-shaped section of the large bowel between the descending colon and the rectum. It is mobile and often loops, which can make it the most uncomfortable part of the test for unsedated patients.
Snare: A wire loop passed through the scope and tightened around a polyp's base to remove it, sometimes with electrical current (hot snare) and sometimes without (cold snare).
Splenic flexure: The bend in the colon near the spleen, where the transverse colon turns downwards into the descending colon. The other natural sharp turn the scope must round.
Split dose: The practice of dividing a bowel preparation into two parts: half the night before, half several hours before the procedure. Split dosing produces noticeably better cleanliness than taking the whole prep the night before. See split dosing.
Surveillance: Coloscopy performed because of an earlier finding (such as a polyp, a cancer treated previously, or long-standing inflammatory bowel disease) rather than as a first screen. Surveillance intervals depend on the earlier findings. See surveillance intervals.
Transverse colon: The portion of the large bowel running across the upper abdomen, between the hepatic and splenic flexures.
Ulcerative colitis: A form of inflammatory bowel disease that affects the lining of the rectum and a continuous portion of the colon above it. See inflammatory bowel disease.
USMSTF: The United States Multi-Society Task Force on Colorectal Cancer, a joint body of the American College of Gastroenterology, the American Gastroenterological Association, and the American Society for Gastrointestinal Endoscopy that publishes consensus recommendations on screening and surveillance.
USPSTF: The U.S. Preventive Services Task Force, an independent panel that issues evidence-based recommendations on preventive services in the United States, including colorectal cancer screening.
Villous: A description of an adenoma's microscopic architecture, with finger-like projections. Villous and tubulovillous adenomas are followed more closely than purely tubular ones because of a slightly higher risk of progression.
Water immersion / water exchange: A technique in which water rather than gas is used to open the bowel during insertion. It is associated with less discomfort, particularly in unsedated examinations, and is used variably between units.

What to ask your clinician

Could you write down the term that came up in my report so I can look it up?
What does this term mean specifically for me, given everything else you know about my case?
Does this finding change what I need to do or come back for?
Is there a difference between the term you used and what I'm reading on the report?

Common worries, briefly addressed

I keep seeing terms I don't recognise on my report.

Pathology reports are written for clinicians, not for patients. The wording can sound alarming when it is, in context, routine. Bring your report to your appointment and ask your clinician to translate the parts that worry you.

Different sources define the same word slightly differently.

That happens. Medicine is a living vocabulary, and some terms (for example, sessile serrated lesion) have changed in the last decade. Where this glossary differs from a definition you have read elsewhere, the difference is usually small; if a clinician uses a particular term in your care, ask them what they mean by it.

Is this list exhaustive?

No. It covers terms used across this site and the most common ones a patient is likely to encounter. If a term you've seen is missing, the contact addresses in the colophon are the best route — we add entries when readers tell us they have looked for them.

Sources

American Society for Gastrointestinal Endoscopy — quality indicators and definitions for colonoscopy
European Society of Gastrointestinal Endoscopy — performance measures for colonoscopy
United States Multi-Society Task Force on Colorectal Cancer — recommendations on follow-up after colonoscopy and polypectomy
World Endoscopy Organization — terminology for colorectal polyps and lesions
British Society of Gastroenterology — endoscopy quality and terminology guidance