Synopsis
Recognise perianal sepsis promptly, map fistula anatomy and rectal inflammation, and combine drainage, continence-preserving surgery and effective Crohn therapy through a specialist multidisciplinary service.
- Perianal Crohn disease includes abscess, fistula, ulceration, fissure, skin tags, stenosis and rectovaginal or anovaginal disease; it may precede recognised luminal inflammation.
- Pain, fever or swelling is an abscess until assessed; urgent examination and drainage take priority over escalating biologic treatment or waiting for elective MRI.
- Pelvic MRI and examination under anaesthesia are complementary: MRI maps tracts and occult collections, while EUA confirms openings and permits drainage or seton placement.
- Assess rectal and upstream luminal Crohn activity because active proctitis worsens healing and changes the chance that local procedures will succeed.
- A loose seton maintains drainage and reduces recurrent abscess while medical therapy controls inflammation; it is not necessarily the final closure strategy.
- Infliximab has the strongest established evidence for complex fistulising disease after sepsis control, with alternatives chosen through current specialist guidance and prior response.
- Antibiotics can treat cellulitis, infection and early drainage symptoms but rarely achieve durable complex fistula closure as sole long-term treatment.
- Protect continence and quality of life: complex fistulotomy can divide sphincter and should not be performed without expert anatomical and functional assessment.
Key red flags
Perianal pain with fever, spreading cellulitis, urinary retention, immunosuppression or sepsis requires urgent colorectal assessment and drainage; antibiotics alone are insufficient source control.
Rapid tissue necrosis, crepitus, severe pain out of proportion or shock suggests necrotising infection and needs immediate emergency surgery and broad antimicrobial treatment.
New faecal vaginal discharge, pelvic sepsis or obstetric tract symptoms needs specialist colorectal and gynaecological assessment rather than repeated empirical antibiotics.
Do not commence anti-TNF or another potent immune therapy through a known undrained collection.
A new irregular ulcer, mass or changing chronic tract warrants biopsy consideration because longstanding fistula disease carries a small malignancy risk.
Investigation priorities
Map primary tract, sphincter relation, secondary branches, horseshoe extension and abscess.
Management branches
Pain, swelling, fever, systemic upset or imaging suggests a perianal abscess.
- Assess ABCDE, analgesia, antibiotics for systemic infection and urgent colorectal review, recognising that deep sepsis can lack a visible fluctuant lump.
- Proceed to timely examination under anaesthesia and incision or internal drainage; obtain MRI first only when stable and it will not postpone source control.
- Place a loose seton when a fistula is identified and ongoing drainage is needed, avoiding definitive sphincter division in an acutely inflamed uncertain field.
- After sepsis control, reassess luminal and rectal disease and plan anti-inflammatory therapy plus interval imaging or EUA.