Decision support only — involve the IBD team and colorectal surgery early for severe colitis, obstruction, abscess or perianal sepsis. Exclude infection before escalating immunosuppression and use current Australian PBS criteria.
1 Phenotype, severity, complication: all three drive treatment
Mild, uncomplicatedambulatory; limited systemic effect
UC: mild bleeding/urgency, limited endoscopic activity. Crohn: low inflammatory burden, no deep ulceration, stricture, penetrating or perianal disease.
Use disease-specific local therapy: optimised oral/rectal 5-ASA for UC; budesonide for selected ileocaecal Crohn. Define a response date.
Moderate–severe / high risksteroid need, deep disease, poor prognostic features
Frequent symptoms, anaemia/weight loss, raised CRP/calprotectin, ulcers, extensive or proximal Crohn, perianal disease, prior admission/surgery.
Induce promptly and plan steroid-free maintenance. Early advanced therapy often makes more sense than cycling steroids/thiopurine alone. ECCO/GESA
Acute severe UC≥6 bloody stools/day + systemic toxicity
Truelove–Witts: tachycardia, fever, Hb <105 g/L, ESR >30 or CRP >30. Admit under gastro + colorectal surgery.
IV steroid, LMWH, stool infection screen and flexible sigmoidoscopy. Assess response on day 3; rescue or colectomy must not drift. ECCO 2026
Crohn complicationsepsis, obstruction, perforation, haemorrhage
Abscess/phlegmon, peritonism, complete obstruction, toxic dilation, fistula with sepsis, uncontrolled bleeding or nutritional failure.
Source control and surgical pathway first. Steroid escalation into an undrained abscess is a bad trade.
Symptoms alone are unreliable: IBS, bile-acid diarrhoea, infection, SIBO and fixed fibrostenosis can all mimic inflammatory activity. Escalate against objective evidence.
2 Diagnose and map disease
Before calling it a flare
- StoolC. difficile testing and culture/multiplex panel as exposure suggests; parasites if travel/risk. Do this before steroids where feasible.
- BloodFBC, CRP/ESR, UEC, LFT/albumin, ferritin/TSAT; B12/folate/vitamin D when relevant. Blood cultures if septic.
- CalprotectinUseful for gut inflammation and serial response, but not specific for IBD; infection, NSAIDs and cancer can raise it.
Establish phenotype
- EndoscopyIleocolonoscopy with segmental biopsies from inflamed and normal-appearing mucosa. Histology helps exclude infection and mimicry.
- Small bowelMRE or intestinal ultrasound; CT enterography when speed/availability wins. Capsule only after obstructive risk is excluded.
- PerianalExamine; MRI pelvis ± examination under anaesthesia for suspected complex fistula/abscess.
Patterns that need another diagnosis
- MimicsInfectious, ischaemic, drug/NSAID, microscopic, diverticular or immune-checkpoint colitis; Behçet, intestinal TB and endometriosis.
- CMVBiopsy ulcer bases in severe/steroid-refractory colitis; blood PCR alone neither proves nor excludes tissue-invasive colitis.
- SerologypANCA/ASCA do not replace endoscopy, histology and imaging.
3 Ulcerative colitis: induction and maintenance
| Setting | Induction | Maintenance / escalation |
|---|
| Proctitis | Mesalazine suppository 1 g daily; add oral 5-ASA if incomplete response or more proximal symptoms. | Continue effective rectal ± oral 5-ASA. Adherence and delivery matter more than brand. |
| Left-sided / extensive mild–moderate | Oral mesalazine at least 2 g/day plus rectal mesalazine ≥1 g/day. Once-daily oral dosing is acceptable. ECCO 2026 | Oral ± rectal 5-ASA. If optimised 5-ASA fails: budesonide MMX 9 mg daily or systemic steroid, then reassess phenotype/adherence. |
| Moderate–severe / steroid-dependent | Short systemic corticosteroid bridge or advanced therapy selected by speed, prior exposure, EIMs, pregnancy plans, infection/VTE/cardiac/malignancy risk and patient preference. | Anti-TNF, vedolizumab, ustekinumab, JAK inhibitor or S1P modulator according to PBS/specialist plan. No steroid maintenance. |
| After response to rescue | Infliximab or ciclosporin pathway in ASUC. | Continue infliximab if it induced response; after ciclosporin, bridge to thiopurine or another durable advanced therapy chosen by the IBD team. |
4 Crohn disease: location and behaviour matter
Luminal disease
- IleocaecalBudesonide 9 mg daily for mild–moderate localised inflammatory disease. It will not fix a fibrotic stricture.
- More severeSystemic corticosteroid can induce; start a steroid-sparing plan at the same time. Thiopurines and methotrexate are too slow for induction.
- AdvancedAnti-TNF, vedolizumab, ustekinumab, upadacitinib and other PBS-listed agents are chosen by phenotype and prior exposure. Combination infliximab + thiopurine can reduce immunogenicity. SONIC
- 5-ASADo not extrapolate UC treatment. Mesalazine has little useful efficacy for active Crohn disease.
Complicated disease
- AbscessAntibiotics + image-guided/surgical drainage where feasible; delay/intentionally sequence immunosuppression until sepsis is controlled.
- ObstructionIV fluid/electrolytes, bowel rest ± NG, cross-sectional imaging and early surgery. Steroids only when inflammatory narrowing is likely and sepsis/perforation excluded.
- PerianalDrain abscess, place seton for complex fistula, then combined medical–surgical care. Infliximab has the strongest RCT evidence; antibiotics are adjuncts.
- Post-opRisk-stratify and prevent recurrence; ileocolonoscopy at 6–12 months, with therapy adjusted to Rutgeerts/endoscopic activity.
5 Acute severe ulcerative colitis: a timed pathway
| When | Do | Decision |
|---|
| Admission / day 0 | Gastro + colorectal surgery; AXR/CT if dilation or complication; stool C. difficile/culture; FBC, CRP, UEC, LFT/albumin; flexible sigmoidoscopy with biopsies within ~24 h. Give LMWH prophylaxis and nutrition. | Start methylprednisolone 60 mg IV daily or hydrocortisone 100 mg IV 3–4 times/day. Avoid opioids, anticholinergics, loperamide and routine antibiotics/TPN. ACG 2025/ECCO 2026 |
| Daily | Stool frequency/blood, vitals, abdominal exam, FBC/CRP/electrolytes/albumin; repeat imaging if dilation or deterioration. | Perforation, toxic megacolon, uncontrolled haemorrhage or worsening systemic toxicity → urgent colectomy, not another drug trial. |
| Day 3 | Objective steroid response. Oxford criterion: >8 stools/day, or 3–8 plus CRP >45 mg/L, predicts high colectomy risk in the original cohort. | If inadequate: infliximab or IV ciclosporin rescue, chosen with surgical and patient factors. Do not continue ineffective steroids to day 7 by habit. |
| After rescue failure | Reassess sepsis/CMV, drug exposure and surgical timing. | Colectomy is standard. Sequential third-line infliximab/calcineurin/JAK rescue is only for highly selected patients in an expert MDT after explicit risk discussion. ECCO 2026 |
6 Advanced therapy: safe setup, then objective follow-up
Before the first dose
- InfectionTB screen; HBsAg/anti-HBc/anti-HBs; HCV/HIV by risk; varicella status; dental/skin focus where relevant.
- VaccinesInfluenza, COVID, pneumococcal, HBV, HPV and recombinant zoster as indicated. Give live vaccines before immunosuppression; avoid during significant immunosuppression.
- RiskMalignancy history, VTE/MACE, pregnancy, heart failure/demyelination, cytopenia, liver/renal function and drug interactions.
Choose deliberately
- Need speedAnti-TNF or JAK inhibitor can act quickly; JAK/S1P agents have specific thrombotic, cardiac, lipid, infection and reproductive cautions.
- EIMsArthritis, psoriasis, uveitis and perianal disease may favour systemic agents; gut-selective vedolizumab may not treat extraintestinal inflammation.
- PBSEligibility and continuation require documented severity and response. GESA’s prescribing guide includes infliximab, adalimumab, vedolizumab, ustekinumab, upadacitinib and UC-specific options; verify the live list.
Treat to target
- EarlySymptoms and CRP/calprotectin after induction. Confirm adherence before declaring mechanistic failure.
- ObjectiveEndoscopy, intestinal ultrasound or MRE to document healing/response. ECCO 2025 gives IUS a larger first-line monitoring role.
- LossFor anti-TNF loss of response, reactive trough/antibody testing can separate underexposure, immunogenicity and mechanistic failure.
7 Health maintenance, pregnancy and cancer surveillance
| Domain | Action | High-yield detail |
|---|
| CRC surveillance | Baseline risk-assessment colonoscopy 8 years after symptom onset for colonic IBD; start immediately at PSC diagnosis. Then use inflammation, extent, PSC, dysplasia, strictures, family history and quality to set interval. | BSG 2025: high-risk 1-year, intermediate 3-year; near-population risk can return to population screening with 10-year reassessment. Visible dysplasia → expert resection + IBD dysplasia MDT. |
| Pregnancy | Aim for remission before conception; active disease is often the larger fetal risk. Continue effective pregnancy-compatible therapy with IBD/obstetric input. | Methotrexate is contraindicated. JAK/S1P and newer agents require product-specific advice. Most biologics are continued when needed; plan infant live vaccines after in-utero exposure. |
| Nutrition / bone / iron | Dietitian; iron studies and replacement; B12 after ileal disease/resection; vitamin D/calcium; DEXA for steroid, malnutrition and other risk. | Exclusive enteral nutrition is effective Crohn induction, especially in children; restrictive diets need supervision. No diet is proven to induce UC remission. |
| General prevention | Smoking cessation (especially Crohn), cervical screening, skin protection/exam by risk, anxiety/depression and sexual-health care. | Avoid NSAIDs when they trigger disease; check VTE prophylaxis for every IBD admission, even with rectal bleeding unless contraindicated. |
Guidelines & reviews. GESA IBD Advanced Therapies Prescription Guide 2024 and current PBS resources; ECCO Crohn therapeutics 2024; ECCO–ESGAR–ESP–IBUS diagnostics/monitoring 2025; ECCO UC therapeutics 2026; ACG UC guideline 2025; BSG adult IBD and colorectal-surveillance guidelines 2025. Trials. SONIC (infliximab/azathioprine), SUCCESS (UC combination therapy), ACT 1/2, GEMINI, UNIFI, SELECTION and pivotal JAK/S1P trials; CYSIF and CONSTRUCT (infliximab vs ciclosporin in ASUC). Caveats. Advanced-therapy PBS eligibility and dosing change often. Oxford day-3 performance is weaker in some modern cohorts; use it as a prompt for a timed MDT decision, not a solitary colectomy order. Verify local CMV, therapeutic-drug-monitoring and perioperative protocols.