Synopsis
Recognise complex perianal Crohn disease, drain sepsis before immunosuppression and combine anatomical, inflammatory and functional assessment to judge treatment response.
- Map both sepsis and inflammation: MRI complements experienced examination under anaesthesia, while rectal assessment identifies proctitis that worsens fistula-healing prospects.
- Drain an abscess and secure drainage before biological therapy; active sepsis or an undrained abscess contraindicates infliximab.
- In eligible adults, selected Remicade induction is 5 mg/kg intravenously at weeks 0, 2 and 6; assess response after all three doses before continuing eight-weekly maintenance.
Key red flags
Escalating pain or fever despite a draining external opening can indicate an undrained branch or blocked seton.
Shock, spreading perineal inflammation or skin necrosis requires emergency assessment for deep or necrotising infection.
New induration, an ulcer, altered discharge or a mass in a longstanding fistula needs assessment for malignancy.
Obstructive symptoms, inability to maintain nutrition or severe luminal activity can complicate the local fistula plan.
Investigation priorities
Define primary and secondary tracts, sphincter involvement and occult collections.
Management branches
A 34-year-old, 70 kg man has persistent active fistulising Crohn disease after conventional therapy.
- MRI shows a complex trans-sphincteric tract with an abscess. The colorectal team drains the collection and inserts a loose seton; subsequent clinical review and imaging assessment confirm adequate drainage with no residual abscess. His prior antibiotics, drainage and immunosuppressive treatment have not controlled fistulising disease, satisfying the conventional-treatment history for specialist infliximab consideration.
- The IBD team documents TB and HBV assessment, appropriate vaccination review, no active infection, no relevant hypersensitivity or moderate/severe heart failure, and reviewed baseline blood counts and organ function. It gives Remicade 5 mg/kg, calculated as 70 × 5 = 350 mg IV over two hours, at weeks 0, 2 and 6, with observation for at least one to two hours after each infusion.
Key medicines
Infliximab — Remicade 100 mg powder for IV infusionAdult fistulising active Crohn disease after the specified conventional-treatment failure or intolerance pathway: 5 mg/kg IV over two hours at weeks 0, 2 and 6, only after abscess drainage and infection exclusion. Observe at least one to two hours after each infusion. If there is no response after three doses, give no further infliximab; responders may continue 5 mg/kg every eight weeks. Specialist treatment and scheduled reassessment are required.Contraindicated with hypersensitivity to infliximab, murine proteins or relevant excipients, active TB or severe infection including abscess/sepsis, and NYHA III–IV heart failure. Screen TB/HBV, review vaccines and exclude active infection before starting. Renal/hepatic impairment has not been studied and no dose recommendation can be made; obtain specialist assessment, not an invented adjustment. Use caution in mild heart failure, demyelination, malignancy history and older adults; stop for serious infection, severe allergy or worsening heart failure. Interrupt an acute infusion reaction immediately with resuscitation capability available. Avoid concurrent live vaccines and other biologics such as anakinra or abatacept. Review thiopurine-combination lymphoma risk, especially in younger men. Consider contraception during treatment and for six months after the final dose; use in pregnancy only if clearly needed. Breastfeeding may be considered, but infant live-vaccine restrictions require a documented plan: after in-utero exposure the selected SmPC recommends 12 months after birth, with its specified specialist exceptions; during maternal treatment while breastfeeding, live vaccine is not recommended unless infant drug levels are undetectable.