High-yield map
Key points before the detail
- 01
Crohn disease is transmural and can be inflammatory, stricturing or penetrating.
- 02
Granulomas are supportive but not required.
- 03
Mesalazine and maintenance steroids are not standard Crohn answers.
- 04
Drain abscesses and perianal sepsis before escalating immunosuppression.
- 05
Surgery treats complications but does not cure Crohn disease.
1. Montreal phenotype
| Axis | Categories |
|---|---|
| Age | A1 ≤16; A2 17–40; A3 >40. |
| Location | L1 ileal; L2 colonic; L3 ileocolonic; L4 upper-GI modifier. |
| Behaviour | B1 inflammatory; B2 stricturing; B3 penetrating. |
| Perianal | Add p for perianal fistulating disease. |
2. Clinical features
- Chronic diarrhoea, abdominal pain, weight loss, fatigue and anaemia.
- Terminal ileal disease may cause B12 deficiency and bile-salt diarrhoea.
- Strictures cause postprandial colic and obstruction.
- Penetrating disease causes abscesses and fistulae.
- Perianal abscess/fistula can precede luminal disease.
3. Diagnosis
- Exclude infection including C. difficile.
- Ileocolonoscopy with segmental biopsies is the core luminal test when safe.
- MR enterography or intestinal ultrasound defines small-bowel activity and strictures without radiation.
- CT is preferred for acute sepsis, perforation or obstruction when speed matters.
- Exclude significant stricture before capsule endoscopy.
- Pelvic MRI maps complex perianal fistulae.
4. Medical principles
- Corticosteroids can induce remission; they must not maintain it.
- Budesonide is an option for selected ileocaecal disease.
- Moderate-to-severe/high-risk disease may need early advanced therapy.
- Mesalazine is not standard effective treatment for active Crohn disease.
- Drain infection before escalating immunosuppression.
5. Stricture and penetrating disease
- Inflammatory narrowing may improve medically; fixed fibrosis will not dissolve with steroids or biologics.
- Acute complete obstruction requires resuscitation, decompression when needed, CT and early surgical review.
- Short accessible strictures may be dilated endoscopically in expert practice.
- Use limited resection or strictureplasty to preserve bowel length.
| Sepsis problem | Management |
|---|---|
| Drainable abscess | Antibiotics plus image-guided drainage where feasible. |
| Undrainable abscess/free perforation | Urgent operative source control. |
| Enterovesical/rectovaginal/enterocutaneous fistula | Define anatomy, control sepsis, optimise nutrition and plan combined medical-surgical treatment. |
6. Perianal Crohn disease
- Pain and fever suggest abscess: drain first.
- Pelvic MRI and EUA map complex tracts.
- Loose setons maintain drainage and protect sphincter.
- Advanced medical therapy is coordinated with drainage; definitive closure waits for controlled rectal inflammation.
7. Surgical principles and recurrence
- Operate for obstruction, abscess/perforation, refractory localised disease, fistula complications, dysplasia/cancer or unacceptable quality-of-life burden.
- Resect only the necessary macroscopic segment unless cancer is suspected.
- Avoid primary anastomosis when sepsis, severe malnutrition, high-dose steroids or poor tissue make failure risk unacceptable.
- Surgery is not curative; perform postoperative recurrence assessment, commonly ileocolonoscopy around 6–12 months after ileocolic resection.
Active recall
Close the notes and answer these
Try each question from memory before revealing the answer. These public prompts are a small preview of the integrated retrieval system inside SurgAtlas.
01What are the three Crohn behaviour phenotypes?
B1 inflammatory/non-stricturing-non-penetrating, B2 stricturing and B3 penetrating.
02Are granulomas required for diagnosis?
No. They are supportive when present but absent in many patients.
03Why must significant stricture be excluded before capsule endoscopy?
Because capsule retention can occur in a narrowed segment.
04What comes first in perianal Crohn disease with an abscess?
Drainage/source control before escalation of immunosuppression.
05Does resection cure Crohn disease?
No. Postoperative recurrence is common and needs risk-based maintenance and surveillance.
Sources & editorial basis
References & editorial basis
- SurgAtlas production source. General Surgery — Crohn's Disease. Public lesson curated from the corresponding production chapter.
- NICE NG129. Crohn's disease: management.
- BSG IBD guideline. British Society of Gastroenterology guidelines on inflammatory bowel disease in adults: 2025.
This lesson is derived from the corresponding SurgAtlas production teaching material. Where the source makes current management or guideline claims, the public lesson uses the cited contemporary guidance. It is written for education and examination preparation, not as patient-specific clinical advice.
Editorial details
Medical Doctor (MD) · MRCS Part A · Physician · Surgical Educator
SurgAtlas is an educational resource. For patient care, verify current national guidance, local antimicrobial and transfusion policies, specialty pathways and individual patient factors.
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