Glossary of IBD Terms

A glossary of inflammatory bowel disease (IBD) terms helps patients, families, and caregivers make sense of common medical language used in clinic visits, test reports, and treatment plans. This article focuses on plain-language explanations of key tests and treatment words seen in Crohn’s disease and ulcerative colitis. It is not exhaustive, but it covers many of the terms that tend to cause confusion.

Key Takeaways

• Many IBD tests look at the bowel directly or measure inflammation in blood or stool.

• Treatment terms often describe goals (like remission), timing (induction versus maintenance), or drug types (such as biologics).

• Understanding words like “treat-to-target” and “mucosal healing” can clarify why doctors repeat tests.

• Therapeutic drug monitoring is about checking medicine levels in blood to guide dosing, not “testing the person.”

• No single test or medicine term stands alone; results and choices are always interpreted in context by the care team.

How this glossary is organized

This glossary is grouped into three sections:

• Tests that look at the bowel or other organs.

• Blood and stool tests that track inflammation and medicine effects.

• Treatment and planning terms that describe medicines and strategies.

Each entry gives a short, plain-language definition. Medical terms appear in parentheses so they match what appears in reports.

Tests that look directly at the bowel

• Colonoscopy: A test where a flexible tube with a tiny camera is passed into the rectum to examine the entire colon and often the end of the small intestine. It also allows biopsies to be taken. (crohnscolitisfoundation.org)

• Flexible sigmoidoscopy (flex sig): Similar to colonoscopy, but usually looks only at the rectum and left side of the colon.

• Upper endoscopy (EGD): A camera test that looks at the esophagus, stomach, and first part of the small intestine from above.

• Capsule endoscopy: A person swallows a small camera capsule that takes pictures through the small intestine and transmits them to a recorder.

• Biopsy: A tiny piece of tissue taken during endoscopy or surgery so a pathologist can examine it under a microscope.

• Histology: The microscopic appearance of tissue on a biopsy. In IBD this looks for chronic inflammation, healing, or changes such as dysplasia (pre-cancer changes).

Imaging tests

• Magnetic resonance enterography (MRE): An MRI scan designed to show the small bowel and other abdominal organs without radiation.

• CT enterography (CTE): A specialized CT scan that gives detailed images of the small bowel and surrounding structures using contrast dye and X‑rays.

• Standard CT scan: Cross-sectional X‑ray pictures of the body used to look for complications such as abscesses or blockages.

• Ultrasound: A test that uses sound waves, sometimes used to look at bowel loops, blood flow, or the liver and gallbladder.

Blood and stool tests

• C‑reactive protein (CRP): A blood marker that often rises when there is active inflammation somewhere in the body.

• Erythrocyte sedimentation rate (ESR): A blood test that reflects general inflammation, usually slower to change than CRP.

• Complete blood count (CBC): A panel that measures red blood cells, white blood cells, and platelets, helping to detect anemia, infection, or medication effects.

• Comprehensive metabolic panel (CMP): A blood panel that checks kidney and liver function, salts, and other chemistry values.

• Iron studies: Blood tests that help tell if a person has iron deficiency, which is common in IBD.

• Vitamin B12 and folate: Blood levels that can drop if parts of the small intestine are inflamed or removed.

• Vitamin D: A blood level that is often low in IBD and may be monitored and supplemented.

• Fecal calprotectin: A stool test that measures a protein released by white blood cells during gut inflammation. High levels suggest active intestinal inflammation and help distinguish IBD from non-inflammatory conditions such as irritable bowel syndrome. (pubmed.ncbi.nlm.nih.gov)

• Stool cultures and infection panels: Tests on stool that look for infections such as C. difficile, which can mimic or worsen an IBD flare.

Treatment goals and strategy terms

• Induction therapy: Treatment used at the start to bring active disease under control and reduce symptoms.

• Maintenance therapy: Ongoing treatment used after improvement to keep inflammation quiet and prevent flares.

• Treat-to-target: A strategy where the care team and patient agree on clear goals, such as no symptoms and healed bowel lining, then adjust treatment until those goals are reached or maintained. (pubmed.ncbi.nlm.nih.gov)

• Clinical remission: Few or no IBD symptoms in daily life, such as normal stool frequency and no bleeding.

• Endoscopic remission / mucosal healing: The bowel lining looks healed or nearly normal on colonoscopy or other scope.

• Deep remission: A stronger form of control that combines feeling well, normal blood or stool markers, and healed bowel on tests.

• Steroid-sparing strategy: A plan that uses other medicines so that long-term steroid use can be avoided.

• Step-up therapy: Starting with milder medicines and moving to stronger ones only if needed.

• Top-down therapy: Starting earlier with stronger medicines, such as biologics, in people with higher-risk disease.

Medicine and delivery terms

• Aminosalicylates (5‑ASA): Anti-inflammatory medicines such as mesalamine that act mainly on the lining of the colon.

• Corticosteroids (steroids): Strong anti-inflammatory drugs, such as prednisone or budesonide, used for short-term control of flares, not as long-term maintenance.

• Immunomodulators / immunosuppressants: Medicines such as azathioprine, 6‑MP, or methotrexate that calm the immune system and help prevent flares.

• Biologic therapy (biologics): Protein-based medicines like infliximab, adalimumab, vedolizumab, or ustekinumab that target specific steps in the immune response to reduce inflammation. (pubmed.ncbi.nlm.nih.gov)

• Biosimilar: A medicine that is highly similar to an original biologic, with no meaningful differences in safety or effect, often used as a more affordable option.

• Small-molecule therapy: Non-biologic pills such as JAK inhibitors or S1P modulators that block specific signaling pathways involved in inflammation.

• Infusion: Medicine given directly into a vein, usually in a clinic or infusion center.

• Subcutaneous injection: Medicine injected under the skin using a syringe or auto-injector pen, sometimes done at home.

• Topical therapy (rectal): Suppositories, foams, or enemas placed into the rectum to treat inflammation in the rectum and lower colon.

Monitoring response to treatment

• Therapeutic drug monitoring (TDM): Blood testing that measures levels of biologic medicines and antibodies against them. It helps tailor the dose or timing to keep drug levels in a useful range and improve chances of remission. (pubmed.ncbi.nlm.nih.gov)

• Trough level: The lowest blood level of a medicine, usually measured just before the next dose, often used in TDM.

• Anti-drug antibodies: Antibodies made by the immune system that attach to a biologic drug, sometimes lowering its effect or causing side effects.

• Loss of response: When a medicine that used to work no longer controls inflammation or symptoms.

• Rescue or salvage therapy: A stronger or different treatment used when standard therapy does not control severe disease, often in hospital settings.

• Remote or home monitoring: Use of home kits or digital tools, such as some home fecal calprotectin tests, to track disease activity between clinic visits. (gastroenterologyandhepatology.net)

FAQs

Does every person with IBD need all of these tests?

No. The specific tests used depend on the type of IBD, symptoms, past results, other health conditions, and the treatment plan designed by the clinical team.

How often are tests like colonoscopy or fecal calprotectin repeated?

Timing depends on disease activity and overall risk. Some people need close monitoring during active disease, then less frequent scopes or stool tests once stable, following guideline-based recommendations and individual circumstances.