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You are likely to hear and read many new medical words when you are diagnosed with Crohn’s or Colitis. It can even feel like a different language. Here we explain some of the terms used most often. You may see them in letters or reports from your health professionals. Or you might hear them during an appointment. If you do not understand a term or find it confusing, ask your doctor, nurse, or pharmacist.
We add more terms to this list whenever we publish new information for the public. We want to grow and improve our information and welcome your feedback. Please email us at evidence@crohnsandcolitis.org.uk with your comments and suggestions.
The explanations in this list are based on information available on the Crohn’s & Colitis UK website and on the following websites:
The colon, rectum and types of Colitis
5-ASA - a type of medicine used to treat mild to moderate flare-ups of Colitis. 5-ASAs are also used to maintain remission and help prevent further flare-ups of Colitis. They are also known as aminosalicylates. See our information on 5-ASAs.
abdomen - often called the belly or tummy. The abdomen is the part of the body between the chest and the pelvis. The abdomen contains the stomach, bowel, liver, spleen and kidneys. The area that contains the abdomen is called the abdominal cavity.
abdominal – things that relate to the tummy, or abdomen, for example, abdominal pain.
abscess - a pus-filled area that becomes red, swollen and painful.
acid reflux – see heartburn.
acute - sudden and severe, but usually lasting a short time.
adalimumab – a biologic medicine used to treat Crohn’s and Colitis. See our information on adalimumab.
adhesions - bands of scar tissue that form between internal tissues and organs. Adhesions usually form after surgery. They attach the area of surgery to another surface, such as a section of gut.
aetiology - the medical cause or causes of diseases and conditions.
allopurinol – a medicine that changes the way azathioprine breaks down in the body. This increases the levels of azathioprine in the blood.
aminosalicylate - see 5-ASA.
anaemia - low numbers of red blood cells in the blood. Red blood cells carry oxygen around the body. Anaemia can cause tiredness and shortness of breath. In Crohn’s and Colitis, anaemia may be due to blood loss. Or it may be due to not eating enough or problems absorbing vitamins or iron.
anal – relating to the anus or bottom.
anal canal - the short passage in your bottom that connects the anus to the rectum. Sometimes called the back passage.
anal fissure - a tear or split in the lining of the back passage, also known as the anal canal. Anal fissures are often painful and may cause bleeding when you poo.
anal fistula – a fistula that connects the anal canal or rectum to the surface of the skin near the bottom, where poo leaves the body.
anal sphincter - a ring of muscles in your bottom that control when it opens and closes. The anal sphincter helps to keep wind and poo in until you are ready to pass them.
analgesic - a type of medicine used to relieve pain. Often called a painkiller, an example is paracetamol. See our information on other treatments for Crohn's and Colitis.
anastomosis - the join between two healthy parts of the bowel after a surgeon has cut out a damaged part of bowel during a resection. See our information on surgery for Crohn’s or Colitis.
antibiotics - medicines used to fight bacterial infections. This includes complications of Crohn’s and Colitis such as an abscess or fistula. See our information on other treatments for Crohn's and Colitis.
antibodies - proteins in the blood that destroy or stop viruses, bacteria and foreign bodies, known as antigens. White blood cells produce antibodies in response to specific antigens. This is part of the body’s immune defence system. Antibodies can also be manufactured as medicines.
anti-diarrhoeal – a type of medicine used to help manage diarrhoea. See our information on other treatments for Crohn's and Colitis.
antigen - a substance, such as a virus or bacteria, that the body’s immune system recognises as foreign.
anti-biologic antibodies – antibodies produced if the immune system recognises a biologic medicine as a foreign substance and thinks it is harmful. This means that the biologic treatment might not work as well over time. See our information on biologics and other targeted medicines.
antispasmodic - a type of medicine used to reduce painful cramps or spasms in the gut. See our information on other treatments for Crohn's and Colitis.
anti-TNF medicines - a type of biologic medicine used to treat Crohn’s and Colitis. Anti-TNF medicines block the effects of an inflammatory protein called TNF-alpha (tumour necrosis factor-alpha). Examples include adalimumab, infliximab and golimumab. See our information on biologics and other targeted medicines.
anus - the opening at the lower end of the gut. The anus may also be called the bottom or back passage. See image.
aphthous erosions or aphthous ulcers - small, shallow sores in the lining of your colon or large bowel. Over time erosions can become deeper and larger and can eventually become deeper ulcers. The term aphthous ulcer is also used more generally for small, painful mouth ulcers that are common in young people.
arthritis - inflammation of a joint, causing pain, swelling and stiffness. The pain in the joints can be called arthralgia.
Acute Severe Ulcerative Colitis (ASUC) - a potentially life-threatening form of Colitis. Symptoms include all those for ‘severe’ Colitis, as well as signs of infection, such as a fever or increased heart rate. ASUC is a medical emergency that requires a stay in hospital for treatment and monitoring.
axial spondyloarthritis, also known as axial SpA - a type of inflammatory disease where the main symptom is back pain. Axial SpA also includes ankylosing spondylitis. About 7% of people with axial SpA also develop Crohn’s or Colitis. See Your Gut | National Axial Spondyloarthritis Society (nass.co.uk)
azathioprine - an immunosuppressant medicine used to treat Crohn’s and Colitis. See our information on azathioprine and mercaptopurine.
bacteria - tiny organisms that exist in the environment and in the body. See microbiota
balloon enteroscopy (single or double) - a special type of endoscope with one or two small balloons at its tip. By inflating and deflating the balloons, the surgeon can move the endoscope further into the small bowel. See our information on tests and investigations.
balsalazide - a 5-ASA medicine used for treating Colitis in the colon.
barium studies (barium enema, barium swallow and meal, and barium follow through) - a type of investigation used to examine the gut. Barium is a white, chalky fluid that is not absorbed into the body. Instead, it forms a temporary coating on the inside of the gut. Because X-rays cannot pass through barium, it provides a clear outline of the gut on an X-ray. See our information on tests and investigations.
beclometasone dipropionate - a steroid medicine used to treat flare-ups of Crohn’s and Colitis. You take it by mouth as a capsule. The capsule has a special coating so that the steroid is not released until it reaches your bowel. See our information on steroids.
bile - a thick, yellow-green liquid produced by the liver. Its main job is to break down fat. See also Primary Sclerosing Cholangitis (PSC).
biologic medicines - a type of medicine used to treat Crohn’s and Colitis. Biologic medicines include anti-TNFs, ustekinumab and vedolizumab. See our information on biologics and other targeted medicines.
biopsy - a small piece of tissue taken from a part of the body for examination under a microscope. These are often taken from the gut during an endoscopy to check for inflammation. This can help to diagnose Crohn’s or Colitis.
biosimilar –different brands of a biologic are slightly different from each other. These slightly different brands are called biosimilars. They are very like the original biologic medicine. See our information on biologics and other targeted medicines.
bloating –a feeling of fullness, pressure or trapped wind in the tummy. See our information on bloating and wind.
bowels – lower part of the gut, also called the intestines. Consists of the small bowel and the large bowel. See image.
bowel incontinence - passing or leaking of poo without meaning to. See our information on bowel incontinence and urgency.
breath tests - simple tests that measure chemicals in the breath. These can help find certain issues with the working of the bowel. Such as lactose intolerance or overgrowth with bacteria.
budesonide – a steroid medicine used to treat flare-ups of Crohn’s or Colitis. See our information on steroids.
bulk-forming laxatives, also called bulking agents – a type of laxative used to treat constipation. Bulk-forming laxatives include bran, ispaghula husk, methylcellulose and sterculia. See our information on diarrhoea and constipation.
bypass – a surgical re-routing (of the bowel).
caecum – the first section of the large bowel, found in the bottom right part of the tummy. See image.
calcineurin inhibitors - immunosuppressant medicines used to treat Crohn's and Colitis. Calcineurin inhibitors used in Crohn's and Colitis include ciclosporin.
calprotectin - a protein made by white blood cells in response to inflammation. See also faecal calprotectin test
capsule endoscopy – a type of endoscopy. An investigation to examine the gut, particularly the small bowel. A small capsule containing a tiny camera is swallowed. As it travels through the gut it takes photographs that are transmitted to a data recorder. See our information on tests and investigations.
colestyramine, colestipol and colesevelam, also known as bile salt binders –medicines used to treat certain types of diarrhoea in Crohn's. See other treatments for Crohn's and Colitis.
chromoendoscopy - a type of endoscopy. Chromoendoscopy involves spraying special dyes onto the lining of the bowel. Sometimes used instead of a biopsy to help to find abnormal cells. See our information on tests and investigations.
chronic - an illness or condition that is ongoing or continues for a long time, such as for at least six months.
ciclosporin - an immunosuppressant medicine used to treat severe Ulcerative Colitis.
ciprofloxacin - an antibiotic sometimes used for Crohn’s. See our information on other treatments for Crohn's and Colitis.
clinical trial - a research study comparing one treatment or test with another.
cobblestoning - appearance of the gut lining seen in Crohn’s that looks like cobblestones. It is formed by deep ulceration and swelling of the surrounding tissue.
codeine phosphate - a painkilling drug also used to help control diarrhoea. See our information on other treatments for Crohn's and Colitis.
colectomy – surgery to remove part or all of the colon. Surgery to remove some of the colon is called a hemicolectomy or partial colectomy. Surgery to remove the whole of the colon is called a total colectomy. See our information on surgery for Crohn’s or Colitis.
colitis - inflammation of the large bowel or colon.
collagenous colitis - a form of Microscopic Colitis in which the lining of the colon develops a thicker than normal layer of collagen. Collagen is a protein that provides structure in the body. See our information on Microscopic Colitis.
colon - part of the large bowel. The colon absorbs water from undigested food waste to form poo. See image.
colonoscopy - a type of endoscopy that is used to examine the rectum, colon and last part of the small bowel. A narrow tube with a camera in its tip, sometimes called a colonoscope, is inserted into the bottom. See our information on tests and investigations.
colostomy – an operation that creates an opening where the large bowel is brought through the abdominal wall to the surface of the tummy. The opening is called a stoma. Digestive waste is then collected in a bag that is fitted over this opening and attached to the skin. A colostomy may be temporary or permanent. See our information on living with a stoma.
complication – a problem that develops after an operation, treatment or illness.
constipation - decrease in the number of times you poo. When constipated, you may not have a poo for several days or even weeks. The poo is hard, dry and lumpy, and can be painful to pass. See our information on diarrhoea & constipation.
corticosteroids - see steroids.
Crohn’s Colitis - a type of Crohn’s where only the large bowel is inflamed. This is because 'colitis' means inflammation of the large bowel. It does not mean you have both Crohn’s Disease and Ulcerative Colitis.
Crohn’s Disease - an Inflammatory Bowel Disease that may affect any part of the gut from the mouth to the bottom. All the layers of the lining of the bowel may become sore and inflamed. See our information on Crohn's Disease.
c-reactive protein (CRP) - a protein in the blood that is often measured to check for active inflammation.
computerised tomography (CT) scan – a scan that uses a series of X-ray beams to build up a detailed picture of the gut. See our information on tests and investigations.
defecation (also spelled defaecation) - having a poo.
dehydration - a condition caused by losing more fluid than you take in. Not drinking enough water or fluids, or losing too much body fluid through sweating, vomiting or diarrhoea, can cause dehydration. See our information on dehydration.
DEXA (dual energy X-ray absorptiometry) scan - a scan that measures how dense or strong your bones are. See our information on bones.
diarrhoea - frequent and often urgent passing of loose or watery poo. It is usually defined as having a loose or watery poo three or more times a day, or more often than is usual for you. See our information on diarrhoea & constipation.
dietitian – a healthcare professional who is qualified to assess and treat dietary and nutritional problems. Qualified dietitians are registered with the Health and Care Professions Council.
dilated - widened.
distal colitis – see left-sided colitis.
distension - an uncomfortable, swollen feeling in the tummy, often caused by gas and fluid in the gut. See our information on bloating and wind.
diverticular disease - a common condition in which small bulges or pouches, called diverticula, form in the wall of the colon. If these become inflamed and infected, this condition is called diverticulitis.
duodenum - the first part of the small bowel. See image.
dysplasia - a change in the size, shape and pattern of normal cells. Dysplasia is not in itself cancer, but it can be a sign that cancer may develop in these cells. Dysplasia can also mean a tissue or organ that does not grow as it should, such as hip dysplasia.
electrolytes – salts and minerals in the blood. Electrolytes include sodium, potassium, and chloride.
elemental diet - see enteral nutrition.
endoscopy - a general name for a test that uses a long, thin, flexible tube called an endoscope with a small camera on the end to look closely at the lining of your gut. An endoscopy is done by an endoscopist, a specially trained doctor, surgeon, or nurse. See also gastroscopy, colonoscopy and sigmoidoscopy.
enema - a liquid or foam inserted into the large bowel through the bottom using an applicator.
enteral nutrition – a liquid diet. If you have a mixture of food and enteral nutrition it’s called partial enteral nutrition. If you only have enteral nutrition it’s called exclusive enteral nutrition. See our information on food.
enteritis - inflammation of the small bowel.
episcleritis - inflammation of the white outer coating of the eye, known as the episclera. Episcleritis is an extraintestinal manifestation (EIM) of Crohn’s and Colitis, which means a symptom outside of the gut.
erythema nodosum - raised, tender red or violet swellings usually on the shins and lower legs during a flare-up. Erythema nodosum is an extraintestinal manifestation (EIM) of Crohn’s and Colitis, which means a symptom outside of the gut.
erythrocytes - see red blood cells.
etiology - the medical cause or causes of diseases and conditions.
exacerbation - a worsening of symptoms or an increase in the activity of the condition. Also known as a relapse or a ‘flare-up’.
extra-intestinal manifestations (EIMs) - symptoms of Crohn’s or Colitis that occur in other parts of the body, outside of the gut.
faecal calprotectin – calprotectin is a protein that is found in poo when there is inflammation of the gut. Increased levels of faecal calprotectin can be a sign of active inflammation in the gut.
faecal calprotectin test – measures the amount of calprotectin in a sample of poo. It is a non-invasive test to show whether you have inflammation in your gut. See our information on tests and investigations.
faecal microbiota transplant (FMT) – a procedure that involves the transfer of poo from a person with a healthy gut to the gut of someone with Crohn’s or Colitis. The aim is to restore a healthy balance of bacteria in the gut.
faecal incontinence – see bowel incontinence.
faeces - waste that remains after food has been digested. Faeces are passed out through the bottom or a stoma. Also known as poo, stools or motions.
fatigue - physical or mental exhaustion or both that does not go away with the usual amount of rest or sleep. See our information on fatigue.
full blood count (FBC) - a blood test that measures the three main types of blood cells - red blood cells, white blood cells and platelets. It is used to check your general health, look for problems such as infections, anaemia and inflammation and monitor people on long-term medicines. See our information on tests and investigations.
ferritin test - a blood test that measures the amount of iron stored in the body. It can be used to tell if anaemia is caused by iron deficiency or by something else. See our information on tests and investigations.
filgotinib – a type of medication, known as a janus kinase (JAK) inhibitor used to treat Ulcerative Colitis. See our information on filgotinib.
fistula - A fistula is when a narrow tunnel develops that connects an organ to another part of your body. These tunnels can connect one internal organ to another, or to the outside surface of the body. A fistula can develop in any part of the body, but many involve the gut. See our information on fistulas.
flare-up - a relapse or worsening of a medical condition in which symptoms are more troublesome. In Crohn’s and Colitis, periods of active inflammation and symptoms are referred to as flare-ups.
flatus - gas from the stomach or bowels let out through your bottom or stoma. Also known as flatulence, wind, farting, or gas. See our information on bloating and wind.
folic acid or folate - a vitamin that is essential for making red blood cells, especially during times of growth and cell division. Folic acid supplements are given to people taking methotrexate to help protect the healthy cells and reduce some of the side effects of methotrexate.
fulminant colitis – see acute severe ulcerative colitis.
gastroenterologist - a doctor who is specially trained in the diagnosis and treatment of gut disorders, including Crohn's and Colitis.
gastrointestinal tract - see gut.
gastroscopy - an examination of the throat, stomach and small bowel. It is also known as an upper gastrointestinal (GI) endoscopy. Gastroscopy uses a slim tube with a camera in its tip, usually called a gastroscope, which is inserted through the mouth. See our information on tests and investigations.
genetics - branch of science that examines how you inherit physical and behavioural characteristics from your parents, including medical conditions. The genes a person inherits is one of a combination of factors that are thought to cause Crohn’s and Colitis.
generic medicine - the active ingredient of a medicine, rather than the brand name it is sold under.
golimumab – an anti-TNF medicine used to treat Ulcerative Colitis. See our information on golimumab.
granuloma - a nodule or lump of non-cancerous inflammatory cells that may be found in the gut wall of people with Crohn's. These can be seen when a biopsy is examined under a microscope.
gut - another word for the digestive system or gastrointestinal tract.
haemoglobin - a protein in red blood cells that carries oxygen around the body.
haemorrhoids - see piles.
heartburn - a burning feeling, usually in the chest, when stomach acid flows up towards the throat.
hepatic flexure - the bend between two parts of the colon – the ascending colon and the transverse colon. Also known as right colic flexure. See image.
hydrocortisone - a steroid medicine used to treat flare-ups of Crohn’s or Colitis. Usually given in hospital by injection or infusion into a vein. See our information on steroids.
IBD or Inflammatory Bowel Disease - An umbrella term for a group of conditions in which the immune system does not work properly and starts attacking the lining of the gut. This causes inflammation and ulcers. Crohn’s Disease and Ulcerative Colitis are the most common forms of IBD. Microscopic colitis and indeterminate colitis (IBDU) are also forms of IBD.
IBD nurse - nursing member of the IBD team with specialist training and knowledge of Inflammatory Bowel Disease. IBD nurses provide expert support and advice for people living with Crohn’s and Colitis that are under the care of their specialist IBD service. Find an IDB nurse.
IBD standards – information about Inflammatory Bowel Disease that sets out what high-quality care looks like at every point of the patient journey, from pre-diagnosis, to surgery and ongoing care, as well as how IBD services should be organised to deliver this.
IBD team - a multidisciplinary team of Consultant Gastroenterologists, Surgeons, Registrars, Pharmacists, IBD Nurse Specialists, Psychologists and Dietitians, all with a specialist knowledge of Inflammatory Bowel Disease.
IBD Unclassified (IBDU) - also known as indeterminate colitis, or as colitis of uncertain type or etiology (CUTE). You may be described as having IBDU if it is unclear whether you have Crohn’s or Colitis.
Irritable Bowel Syndrome (IBS) - Irritable Bowel Syndrome is sometimes confused with Inflammatory Bowel Disease (IBD) but is a different condition. Some of the typical symptoms of IBS, such as diarrhoea and tummy pain, can be very similar to those of IBD. But IBS does not cause inflammation or bleeding.
ileal pouch-anal anastomosis (IPAA) - an operation to create an internal pouch after the colon has been removed. The pouch is made from the lower part of the small bowel, known as the ileum, and attaches to the anus. This means you can poo out of your bottom in the usual way. Sometimes called restorative proctocolectomy or ‘j-pouch’ surgery. See our information on surgery for Crohn’s or Colitis.
ileocaecal valve - a muscular valve that separates the small bowel from the large bowel. The ileocaecal valve prevents food from flowing from the colon back into the small bowel.
ileorectal anastomosis - an operation to attach the end of the small bowel, known as the ileum, to the rectum after the colon has been removed. This means you can poo out of your bottom in the usual way. See our information on surgery for Crohn’s or Colitis.
ileostomy – a surgical opening where a section of your small bowel is brought out through the wall of the tummy to create an opening called a stoma. Poo is then collected in a bag, which is fitted over this opening and attached to the skin. An ileostomy may be temporary or permanent. See our information on surgery for Crohn’s or Colitis.
ileum - the lower part of the small bowel. The ileum joins the colon at the ileocaecal valve. See image.
ileitis - inflammation of the ileum.
immune system - the body’s defence system. This is made up of different types of tissues and cells that protect the body by recognising and attacking infectious or other harmful organisms that may cause illness.
immunology - the study of the body's immune system.
immunomodulators – medicines that act by modifying the immune system. This includes thiopurines and methotrexate. These medicines are also immunosuppressants.
immunosuppressants – medicines that reduce or ‘suppress’ the immune system. This includes steroids, thiopurines, methotrexate, calcineurin inhibitors, janus kinase (JAK) inhibitors and biologics.
incontinence - passing or leaking of poo or pee without meaning to. It may be called bowel incontinence if it’s poo, or urinary incontinence if it’s pee. See our information on bowel incontinence and urgency.
indeterminate colitis - see IBD Unclassified.
induction treatment - treatment to ease the inflammation in your gut and get your Crohn’s or Colitis under control.
inflammation - the way the body responds to irritation, infection or injury. White blood cells and other immune cells collect in affected areas, causing reddening, swelling and pain.
inflammatory bowel disease – see IBD
infliximab - an anti-TNF medicine used to manage Crohn’s and Colitis. See our information on infliximab.
infliximab trough level - the lowest concentration of infliximab in the blood, measured just before the next dose is due. This helps your doctor know how you are responding to infliximab treatment.
infusion - a procedure to inject a medicine or other liquid into the bloodstream at a steady rate over a period of time. The fluid flows from a sterile bag through plastic tubing and a small needle into a vein.
intestines – see bowel.
intramuscular (IM) - into a muscle.
intravenous (IV) - into a vein.
iritis - inflammation of the coloured part of the eye, knowns as the iris. Also called anterior uveitis.
isotope scan - see nuclear scan.
-itis - inflammation of a part of the body, for example colitis means inflammation of the colon.
J-pouch – a pouch created out of part of the small bowel after surgery to remove the large bowel. A pouch that is surgically created from the small bowel. A J-pouch is made during an operation to remove the large bowel. See our information on surgery for Crohn’s or Colitis.
JAK (Janus kinase) inhibitor - JAKs are proteins that play a part in activating the body’s immune response. This can cause gut inflammation in Crohn’s and Colitis. JAK inhibitors block the effects of JAKs, easing inflammation in the gut. Examples include filgotinib, tofacitinib and upadacitinib. See our information on biologics and other targeted medicines.
jejunum - the section of small bowel between the duodenum and the ileum. See image.
key-hole surgery - see laparoscopy.
lactose - a sugar found in dairy products, like milk, cream and cheese. An enzyme called lactase, which is found in the lining of your small bowel, usually breaks it down so your body can absorb it.
lactose intolerance - when you become unwell from eating foods that contain a protein called lactose. This can happen because your body doesn’t produce enough enzymes to break lactose down. Lactose intolerance can cause symptoms like diarrhoea, bloating, wind, tummy pain and feeling sick. See our information on food.
laparoscopy - a procedure in which the surgeon makes four or five small cuts in the tummy. A small camera called a laparoscope, a light and surgical tools are passed through the cuts to carry out surgery. Also known as key-hole surgery.
large bowel - the part of the bowel that comes after the small bowel in the digestion process. It includes the colon, rectum and anal canal. It is where nutrients are absorbed and poo is formed. See image.
laxative - a medicine that helps you to have a poo. See our information on diarrhoea & constipation.
left-sided colitis - colitis where the inflammation is in parts of the colon on the left side of the body, known as the distal colon. Left-sided colitis is also called distal colitis. See image.
lesion - damage or unusual change to tissue anywhere in the body. Usually caused by disease or trauma.
leucocytes - white cells in the blood that help to fight infection. Leucocytosis is a larger number of white cells in the blood, while leucopaenia is a smaller number of white cells in the blood.
liver function tests (LFTs) - blood tests that measure certain proteins and enzymes in the blood to show how well the liver is working.
liquid diet - see enteral nutrition.
liver - the largest gland in the body, with many functions. Its main function is to regulate chemicals in the blood.
lymphocytic colitis - a form of Microscopic Colitis in which the inner lining of the gut has more white blood cells, known as lymphocytes, than usual. See our information on Microscopic Colitis.
maintenance therapy - treatment that usually involves one or more medicines that are taken long-term to keep an illness under control.
malabsorption - not being able to fully absorb the nutrients in food through the gut.
MAP (mycobacterium avium subspecies paratuberculosis) - an organism that causes a disease in cattle similar to Crohn’s Disease. There is ongoing debate as to whether MAP is involved in Crohn’s.
mercaptopurine - a thiopurine medicine, similar to azathioprine, used to treat Crohn’s and Colitis. Also called 6-mercaptopurine or (6-MP). See our information on azathioprine and mercaptopurine.
mesalazine - a 5-ASA (aminosalicylate) medicine used to treat Colitis. See our information on 5-ASAs (aminosalicylates).
methotrexate - an immunosuppressant medicine used to treat Crohn’s, and occasionally Colitis. See our information on methotrexate.
metronidazole - an antibiotic that may be used to treat inflammation in Crohn’s, abscesses and fistulas. See our information on other treatments for Crohn's and Colitis.
microbiota – the variety of bacteria, viruses, fungi, and other microorganisms that live in one place, such as the gut.
Microscopic Colitis - a form of Inflammatory Bowel Disease in which the inner lining of the gut wall becomes inflamed. This change can only be seen when a sample of tissue, known as a biopsy, is taken from your colon and looked at under a microscope. See our information on Microscopic Colitis.
MRI (magnetic resonance imaging) scan - an examination of the inside of the body using strong magnets and radio waves rather than X-rays.
MRI enteroclysis/enterography - types of MRI scans used to assess the small and large bowel using a gas or a liquid, called a contrast dye, to give clearer images. In an enteroclysis test, gas or liquid is passed into the intestine through a tube. In an MRI enterograph, the liquid is drunk. See our information on tests and investigations.
mucus - a white, jelly-like fluid produced by the lining of the gut, known as the mucosa. People with Crohn’s or Colitis may have a lot of mucus in their poo.
mycophenolate mofetil - an immunosuppressant medicine occasionally used to treat Crohn’s and Colitis.
nasogastric tube - a tube that goes through your nose, down your throat and into your stomach. If you are having enteral nutrition, your liquid food might be given by a nasogastric tube. See enteral nutrition.
NICE (National Institute for Health and Care Excellence) - an organisation that provides national guidance and advice to improve health and social care.
NSAIDs (non-steroidal anti-inflammatory drugs) – anti-inflammatory painkillers, often used to manage inflammatory conditions. Examples of NSAIDs include ibuprofen and diclofenac. There is some evidence that they may make Crohn’s and Colitis worse.
nuclear scan - a scan in which a small amount of a radioactive substance, known as a tracer, is taken into the body, usually by injection. This radioactive substance gives out energy that can be detected by a special camera. Nuclear scans can show the structure of body organs and tissues. See our information on tests and investigations.
obstruction - a blockage of the bowel, often caused by a narrowing or a stricture.
occult blood - blood that cannot be seen by the naked eye. A faecal occult blood test checks your poo for blood that cannot be seen.
oedema - swelling caused by fluid gathering in the tissues.
oesophagus (gullet) – part of your gut that connects your mouth to your stomach. This muscular tube helps you swallow food and drink. See image.
olsalazine - a 5-ASA medicine used for treating Ulcerative Colitis. See our information on 5-ASAs (aminosalicylates).
oral Crohn’s - Crohn’s in the mouth.
osteoporosis - weakening of the bones making them fragile and more likely to break. It is more common in people with Crohn’s or Colitis than in the general population. This may be due to long-term use of steroids, severe active disease or by low levels of oestrogen, a type of female sex hormone. See our information on bones.
osteopenia - a mild weakness of the bones, which is not as severe as osteoporosis. See our information on bones.
ostomy – an operation to make an opening in the wall of the stomach. In Crohns or Colitis, a surgeon can direct part of the bowel through the opening, making a new way for poo to leave your body. See our information on stoma.
ozanimod - an S1P receptor modulator used to treat adults with moderate to severely active Ulcerative Colitis. See our information on ozanimod.
paediatrician - a doctor who specialises in the care of children and young people.
pancolitis - see total colitis
parenteral nutrition - a way of giving a specially prepared liquid food into a vein when nutrients cannot be absorbed through the gut. Also called total parenteral nutrition or total parenteral nutrition (TPN).
pathogen - a harmful organism, such as a bacterium or virus, that causes disease.
pathology - the study of medical conditions, including what causes it and the effect it has. A pathologist is a doctor who specialises in looking at samples of tissues, known as biopsy, blood, poo or pee to look for disease.
perforation - a rupture of the bowel. This creates a hole in the bowel wall. Sometime poo (digested food) may leak through it.
perianal - the area around the bottom or anus.
peristalsis - the wave of muscle contractions that move food through the gut.
peritoneum - the thin layer of tissue that lines the inside of the abdominal cavity in the tummy.
Peritonitis – inflammation of the peritoneum, often due to a perforation of the bowel wall.
PET (positron emission tomography) scan – a scan that gives a clear 3-D image of the inside of the body. A PET scan can show how well certain parts of your body are working.
piles – swollen veins in or around the bottom that bleed easily and can become painful. Also called haemorrhoids.
polyp – a small growth on the lining of the bowel.
pouch (ileo-anal) – an internal pouch or reservoir made from the lower part of the small bowel, known as the ileum, and attaches to the anus. This allows poo to pass through your bottom in the usual way. See our information on surgery for Crohn’s or Colitis.
pouchitis – inflammation of an ileo-anal pouch.
prebiotic – a natural fibre that humans cannot digest. Prebiotics are found in foods such as bananas and leeks. The good bacteria in the gut feed on this fibre.
prednisolone – a steroid medicine used to ease inflammation in a flare-up of Crohn’s or Colitis. See our information on steroids.
primary sclerosing cholangitis (PSC) – a rare condition that causes inflammation of the bile ducts and can eventually damage the liver. Primary sclerosing cholangitis affects about 1 in 50 people with Crohn’s and 1 in 20 people with Colitis.
probiotics – live bacteria found in certain foods or supplements.
proctitis – inflammation in the rectum, which is the last part of the large bowel. See image.
proctocolectomy – a type of surgery in which the whole colon, rectum and anal canal are removed. The surgeon makes an ileostomy (stoma) by joining a section of the small bowel to the surface of the tummy. Also called total colectomy. See our information on surgery for Crohn’s or Colitis.
proctosigmoiditis – inflammation of the rectum and part of the colon that’s just above the rectum, known as the sigmoid colon.
product licence – the document that explains what a medicine can be used for.
prognosis – a prediction of what might happen in the future, or the likely progress of a condition.
prophylactic therapy – preventive treatment.
proteins – organic compounds made up of amino acids. Proteins are important for the health and growth of the body’s cells and tissues.
pus – a thick, white, yellow, or greenish fluid, made up of dead cells, tissue and bacteria. Often produced when the body is trying to fight off an infection.
pyoderma gangrenosum – a skin condition that starts as small tender blisters that become painful ulcers. Pyoderma gangrenosum can affect people with Crohn’s or Colitis and is sometimes, but not always, linked to a flare-up. It is most often found on the legs or near a stoma.
radiologist – a doctor who specialises in interpreting X-ray, ultrasound and other types of imaging or scanning examinations.
rectal bleeding – any blood that is passed out through your bottom.
rectum – the last part of the large bowel. See image.
red blood cells – cells in the blood that transport oxygen around the body. Also called erythrocytes.
relapse – symptoms becoming worse after a period of improvement. Often called a ‘flare-up’.
remission – a period of good health, free of active disease, with few or no symptoms.
resection – the surgical removal of a part of the bowel. See our information on surgery for Crohn’s or Colitis.
restorative proctocolectomy – see ileal pouch-anal anastomosis.
rheumatologist – a doctor with special training in the diagnosis and treatment of people with joint and muscle problems.
right hemicolectomy – an operation to remove parts of the bowel, known as the terminal ileum and caecum. See our information on surgery for Crohn’s or Colitis.
risankizumab – a type of biologic medicine known as an interleukin IL-23 antagonist. Risankizumab is used to treat Crohn’s. See our information on risankizumab.
sacroiliac joints – joints in the lower back between the pelvis and the spine. These may become inflamed and painful in some people with Crohn’s or Colitis. This condition is called sacro-ilitis.
Scottish medicines consortium (SMC) – the national source of advice on the clinical and cost-effectiveness of all new medicines for NHS Scotland.
septicaemia – a life-threatening reaction to an infection. The immune system overreacts and starts to damage the body’s own tissues and organs. Septicaemia is sometimes called blood poisoning or sepsis.
seton – a piece of surgical thread passed through an anal fistula and out of the bottom. The ends of the thread hang out of your bottom, allowing the pus or infected tissue to drain away. See our information on surgery for Crohn’s or Colitis.
short bowel syndrome – where the bowel is not able to absorb enough nutrients. This can happen if large sections of the small bowel, and sometimes all or part of the large bowel, have been removed.
sigmoid colon – the lower end of the colon, connecting the descending colon to the rectum. See image.
sigmoidoscopy – an examination of the rectum and the lower colon. A specialist inserts a short, flexible tube with a camera in its tip, called a sigmoidoscope, into your bottom.
small bowel enema – a type of test or investigation to examine the small bowel. Liquid barium is passed into the small bowel through a fine tube that’s inserted into the nose or mouth. This helps give clearer X-ray images. See our information on tests and investigations.
small bowel - the section of the bowel that digests food and absorbs nutrients after they have passed through the stomach. The small bowel is divided into three parts: the upper region – called the duodenum; the middle region - the jejunum; and the lower region - the ileum. Also called the small intestine. See image.
small intestine bacterial overgrowth (SIBO) – an unusually high number of bacteria in the small bowel.
splenic flexure – where two parts of the colon meet - the transverse colon and the descending colon. See image.
steroids - a group of hormones used as a medical treatment to control Crohn’s and Colitis. These include prednisolone, budesonide and hydrocortisone. Also known as corticosteroids. See our information on steroids.
stoma - an opening on the wall of your tummy made during surgery that brings your bowel to the outside. If you have a stoma, the contents of your gut do not travel all the way through your bowel to come out of your bottom. Instead, they come out of the stoma into a bag you wear on your tummy. See our information on living with a stoma.
stricture - a narrowing of a section of the bowel caused by bowel wall thickening, inflammation, or scarring.
stricturoplasty - an operation to widen a narrow section of the bowel, so that food matter or waste can pass through more easily.
sulfasalazine (Salazopyrin) - a 5-ASA medicine used to treat Colitis. See our information on 5-ASAs (aminosalicylates).
suppository - a small waxy bullet-shaped capsule that is inserted into the bottom. This allows the medicine to act directly on the affected area.
sutures - stitches.
synbiotic - a mixture of prebiotics and probiotics.
tacrolimus - an immunosuppressant medicine, similar to ciclosporin. Sometimes used to treat severe Crohn’s and Colitis that doesn’t respond to other treatments. See our information on other treatments for Crohn's and Colitis.
tenesmus - a constant feeling of needing to have a poo, even when the bowel is empty.
terminal ileum - the last part of the small bowel before it joins the large bowel. See image.
thiopurines - a group of immunosuppressant medicines that includes azathioprine and mercaptopurine. See our information on azathioprine and mercaptopurine.
thiopurine metabolites (TGNs) - small molecules that are made when azathioprine or mercaptopurine are broken down in the body. Looking at the levels of these molecules in blood can suggest whether the right dose of medication is being given or if there is a risk of liver damage. See our information on azathioprine and mercaptopurine.
tofacitinib - a janus kinase (JAK) inhibitor used to treat Ulcerative Colitis. See our information on tofacitinib.
topical treatment - drug treatment applied straight to an affected area of the body. In Crohn’s and Colitis, this usually means using suppositories and enemas to treat inflammation in the rectum or the lower section of the colon.
total colectomy - see proctocolectomy.
total colitis - inflammation of the entire colon. See image.
toxic megacolon - extensive and severe inflammation in the colon that causes gas to become trapped. The colon becomes so swollen that there is a danger of rupture.
TPMT (thiopurine methyltransferase) - an enzyme in blood that can be measured to predict the possibility of side effects from thiopurine medicines, such as azathioprine or 6-MP.
TPN - total parenteral nutrition. See parenteral nutrition.
transition - the stage when a young person moves from paediatric (child) healthcare to adult healthcare. This usually happens between the ages of 14 to 18. See our information on transition to adult care.
tumour - an abnormal growth that may be benign, known as non-cancerous, or malignant, known as cancerous.
U&E (urea and electrolytes) - a blood test that mainly checks how the kidneys are working.
ulcer - an open sore that can be on the inside or outside of the body.
Ulcerative Colitis - an Inflammatory Bowel Disease in which the immune system starts attacking the lining of the gut. This causes inflammation and ulcers in the colon and rectum (the large bowel).
ultrasound scan – a scan that uses sound waves to make detailed images of organs in the body. In Crohn’s and Colitis, an ultrasound scan can show thickening of the bowel wall, abscesses and strictures. See our information on tests and investigations.
upadacitinib- a janus kinase (JAK) inhibitor used to treat moderate to severely active Crohn's or Colitis. See our information on upadacitinib.
ustekinumab - a biologic medicine used to treat moderate to severely active Crohn’s or Colitis. See our information on ustekinumab.
uveitis - inflammation of the eyes that causes redness or soreness. Uveitis can affect people with Crohn’s or Colitis.
urgency – a sudden intense feeling of needing to poo and having to rush to get to the toilet. See our information on bowel incontinence and urgency.
vaginal Crohn’s – when Crohn’s spreads to the vulva or vagina following a fistula in or around the bottom.
vedolizumab - a biologic medicine used to treat moderate to severely active Crohn’s or Colitis. See our information on vedolizumab.
virus – a small germ that uses living cells to reproduce. Common viral infections in humans include colds, flu, COVID-19 and norovirus.
vitamin D – a vitamin that keeps your bones, teeth and muscles healthy. It’s made by the skin when in sunlight.
white blood cells – cells of the immune system that help protect the body from infection. Also called leukocytes or leucocytes.
X-ray – a type of radiation that passes through the body to make pictures of the inside of the body on photographic film. Bones, muscles and organs absorb different amounts of radiation, so the pictures show different body parts in varying shades of light and dark. See X-ray - NHS (www.nhs.uk).
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We know it can be difficult to live with, or support someone living with these conditions. But you’re not alone. We provide up-to-date, evidence-based information and can support you to live well with Crohn’s or Colitis.
Our helpline team can help by:
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