Synopsis
Diagnose and phenotype Crohn disease across the gastrointestinal tract, distinguish inflammation from structural damage, and choose timely medical, nutritional, endoscopic or surgical care.
- Crohn disease causes discontinuous transmural inflammation anywhere from mouth to anus, most often involving terminal ileum or colon, and may produce strictures, fistulae or abscesses.
- Diagnosis requires compatible clinical, endoscopic, histological and imaging evidence after excluding infection and other mimics; no single blood or stool marker is diagnostic.
- At diagnosis document location, inflammatory versus stricturing or penetrating behaviour, perianal involvement, upper gastrointestinal disease, growth or nutrition and extra-intestinal manifestations.
- Ileocolonoscopy with segmental biopsies and small-bowel cross-sectional imaging are complementary because normal colonic appearances do not exclude proximal transmural disease.
- Symptoms may arise from active inflammation, fixed fibrosis, bile-acid diarrhoea, bacterial overgrowth, infection, irritable bowel physiology or medication effects; escalation only helps when the mechanism is right.
- Corticosteroids or exclusive enteral nutrition can induce remission in selected disease but are not maintenance treatments; repeated steroid exposure signals treatment failure.
- Early advanced therapy is considered when prognostic risk is high, disease is extensive or severe, or conventional therapy is unlikely to prevent damage, following current BSG and NICE pathways.
- Abscess needs drainage and infection control, obstruction needs urgent structural assessment, and surgery can be the best disease-modifying option for localised complications rather than a failure of care.
Key red flags
Peritonism, sepsis, a tender mass or free perforation requires emergency surgical and gastroenterology assessment rather than empiric steroid escalation.
Persistent vomiting, distension, absolute constipation or escalating colic suggests obstruction and needs urgent imaging with intravenous fluids and surgical input.
Painful perianal swelling with fever is an abscess until assessed; do not wait for biologic optimisation before securing drainage.
Major bleeding, severe dehydration, venous thromboembolism, toxic dilatation or acute kidney injury warrants inpatient multidisciplinary care.
Before attributing deterioration to a flare, exclude enteric infection, including Clostridioides difficile where relevant, and assess for abscess.
Investigation priorities
Quantify inflammation, complications and treatment readiness.
Management branches
Persistent gastrointestinal, perianal, nutritional or extra-intestinal features suggest Crohn disease.
- Assess symptom pattern, weight, smoking, family history, medicines, infection exposure, perianal symptoms, growth and extra-intestinal features, with examination for complications.
- Obtain blood, faecal inflammatory and microbiological tests, arranging urgent imaging first when obstruction, abscess or perforation is possible.
- Complete ileocolonoscopy with biopsies and small-bowel imaging, adding upper endoscopy or capsule selectively when the suspected distribution remains unresolved.
- Record anatomical extent, behaviour, perianal disease, objective activity, nutrition and prognostic risk in a shared baseline plan.