Glossary of IBD Terms

Inflammatory bowel disease care uses many medical words. This glossary explains common test and treatment terms in plain language. It covers lab and stool tests, scopes and imaging, medicine classes, dosing language, monitoring, and key procedures. The goal is to help families understand results, discuss options with the care team, and follow a treatment plan with confidence.

Key takeaways

• Common blood and stool tests track inflammation and treatment response.

• Scopes and imaging show where inflammation is and how active it is.

• Medicines fall into clear groups, each with benefits and risks.

• Dosing, monitoring, and switching terms explain how plans change over time.

How this glossary is organized

Terms are grouped by topic. Each term is defined in one or two simple sentences. Details may differ by person, so care teams tailor plans.

Tests and monitoring

• Fecal calprotectin (FC): A stool protein that reflects gut inflammation. High values suggest active disease.

• C‑reactive protein (CRP): A blood marker of inflammation made by the liver. It rises during flares.

• Erythrocyte sedimentation rate (ESR): A slower blood test of inflammation. It may lag behind symptoms.

• Complete blood count (CBC): Checks red cells, white cells, and platelets. It screens for anemia and infection.

• Comprehensive metabolic panel (CMP): Blood tests for electrolytes, kidney, and liver health.

• Iron studies: Ferritin and transferrin saturation show iron levels and help guide anemia treatment.

• Vitamin B12 and vitamin D: Levels may drop in IBD, especially with small bowel disease or limited diets.

• Therapeutic drug monitoring (TDM): Blood tests that measure medicine levels and antibodies to guide dosing.

• Trough level: The lowest blood level of a drug, taken right before the next dose.

• Anti‑drug antibodies (ADAs): Immune proteins that can lower biologic drug levels or block effect.

• TPMT and NUDT15 testing: Blood or genetic tests that predict thiopurine safety and dosing.

• Tuberculosis and hepatitis screening: Safety checks before starting immunosuppressive therapy.

• Stool pathogen panel: Tests for infections that can mimic an IBD flare.

• Colonoscopy: A camera exam of the rectum and colon with biopsies to confirm and stage disease.

• Flexible sigmoidoscopy (flex sig): A shorter scope of the rectum and left colon, often used for quick checks.

• Upper endoscopy (EGD): A scope of the esophagus, stomach, and first part of the small intestine.

• Capsule endoscopy: A swallowed camera that pictures the small bowel. It is avoided if strictures are suspected.

• MRI enterography (MRE): MRI pictures of the small bowel without radiation. It shows inflammation and fistulas.

• CT enterography (CTE): CT pictures of the small bowel with X‑rays. It is fast, but uses radiation.

• Intestinal ultrasound (IUS): Bedside ultrasound of bowel wall thickness, blood flow, and complications.

• Pathology and biopsy: Microscopic review of tissue to confirm IBD and look for chronic changes.

• Dysplasia: Abnormal cells in the colon that can be precancerous and need close follow‑up.

• DEXA scan: A bone density test, often used after steroid exposure or if fracture risk is high.

Treatments and medicines

• Aminosalicylates (5‑ASA): Anti‑inflammatory medicines for mild to moderate ulcerative colitis. Pills, enemas, or suppositories.

• Corticosteroids: Fast symptom control during flares, not for long‑term use because of side effects.

• Budesonide: A steroid that mostly acts in the gut, with fewer whole‑body effects.

• Immunomodulators: Drugs that calm immune activity, such as thiopurines and methotrexate.

• Thiopurines (azathioprine, 6‑MP): Maintenance drugs that work slowly and require regular labs.

• Methotrexate: A weekly medicine for Crohn’s, paired with folic acid and lab monitoring.

• Biologics: Lab‑made proteins that target specific immune pathways to reduce inflammation.

• Anti‑TNF agents: Biologics that block tumor necrosis factor. Examples include infliximab and adalimumab.

• Anti‑integrin therapy: Biologics like vedolizumab that are gut‑selective with a favorable safety profile.

• IL‑12/23 and IL‑23 inhibitors: Biologics such as ustekinumab, risankizumab, and mirikizumab targeting interleukins.

• JAK inhibitors: Oral drugs like tofacitinib and upadacitinib that work quickly, with specific safety checks.

• S1P receptor modulators: Oral drugs such as ozanimod and etrasimod that keep white cells in lymph nodes.

• Topical therapy: Rectal 5‑ASA or steroids as enemas, foams, or suppositories for distal disease.

• Antibiotics: Used for infections or perianal complications, not as routine IBD control.

• Induction therapy: The first treatment phase to bring symptoms and inflammation under control.

• Maintenance therapy: Ongoing treatment that keeps remission and prevents flares.

• Loading dose: Higher or more frequent early doses to reach effective drug levels.

• Infusion: Medicine given into a vein at a clinic or infusion center.

• Injection: Medicine given under the skin at home or in a clinic.

• Combination therapy: Two medicines used together, often a biologic plus an immunomodulator.

• Step‑up therapy: Starting with milder medicines, adding stronger ones if disease stays active.

• Top‑down therapy: Starting with advanced medicines for high‑risk or severe disease.

• Bridging therapy: Temporary steroids while waiting for another drug to start working.

• Biosimilar: A highly similar version of a biologic with no meaningful differences in safety or effect.

• Interchangeable biosimilar: A biosimilar that can be substituted for the reference product under set rules.

• Treat‑to‑target (T2T): A strategy that sets clear goals, then adjusts therapy to reach them.

• Clinical remission: Few or no symptoms in daily life.

• Biomarker remission: Normal CRP and fecal calprotectin.

• Endoscopic remission: Healed lining on scope, often called mucosal healing.

• Histologic remission: Normal or near‑normal appearance of tissue under the microscope.

Procedures and surgery

• Seton: A soft thread placed through a fistula to keep it open and draining.

• Abscess drainage: A procedure to drain a pocket of infection, often with antibiotics.

• Endoscopic balloon dilation: A scope‑guided stretch of a short bowel narrowing.

• Strictureplasty: Surgery that widens a narrowed segment without removing bowel.

• Resection: Surgery that removes a diseased section of intestine.

• Ostomy: An opening on the abdomen where stool leaves the body into a bag.

• Ileostomy or colostomy: An ostomy from the small bowel or colon, depending on surgery type.

• IPAA (J‑pouch): A surgically made internal pouch after colectomy for ulcerative colitis.

• Pouchitis: Inflammation of the pouch that often improves with antibiotics.

FAQs

Which tests check inflammation without a scope?

Fecal calprotectin and CRP are the most common. They help track response between scopes.

How long until advanced therapies start working?

Many biologics and JAK inhibitors show benefit in about 2 to 12 weeks. Full response can take longer.

Why is drug level testing done?

Therapeutic drug monitoring helps decide whether to adjust dosing, add a partner drug, or switch therapies.

When is a bone density test needed?

A DEXA scan is considered when steroid exposure or other fracture risks are present. The care team advises timing.