Inflammatory bowel disease: diagnosis, treatment, and GP shared care in AU

IBD — chronic, relapsing, and very manageable with the right team

Inflammatory bowel disease (IBD) encompasses Crohn’s disease and ulcerative colitis — two distinct but related conditions sharing a common thread: chronic, immune-mediated inflammation of the gut that follows a relapsing-remitting course over a lifetime. Together they affect approximately 85,000 Australians, with incidence rising over recent decades and one of the highest rates globally per Crohn’s & Colitis Australia.

Peak onset is in the second and third decade of life, with a second smaller peak in the fifth and sixth decades. Family history is present in about 10–25% of cases. Smoking is protective for ulcerative colitis but worsens Crohn’s disease — one of the clearest environmental signals in gastroenterology.

The therapeutic landscape has transformed over the past decade. Advanced therapies — biologics and JAK inhibitors — achieve mucosal healing and sustained remission in patients where older treatments failed. The GP’s role is not to initiate these medications, but to provide essential shared care: monitoring, vaccination, bone health, nutritional screening, mental health support, and coordinating cancer surveillance.

A. Core clinical — the AU general-practice framework

Distinguishing Crohn’s from UC

Ulcerative colitis causes mucosal (surface-layer only) inflammation confined to the colon, spreading continuously from the rectum upward. Extent determines severity: proctitis (rectum only), left-sided disease, or extensive/pancolitis. Hallmark symptoms are bloody diarrhoea, urgency, and tenesmus. UC is surgically curable via colectomy.

Crohn’s disease causes transmural (full-thickness) inflammation that can involve any segment from mouth to anus, typically with skip lesions — inflamed segments separated by normal bowel. Terminal ileum and colon are most commonly affected. Complications include fibrostenotic strictures, penetrating fistulae, abscesses, and perianal disease. It is not curable by surgery — postoperative recurrence is high.

History

The IBD history covers: stool frequency, consistency, presence of blood or mucus, urgency and tenesmus, abdominal pain, weight loss, fevers, perianal symptoms (skin tags, fissures, discharge). Extraintestinal manifestations are reported in 25–40%: joint pain (peripheral or axial arthritis), eye symptoms (uveitis, episcleritis), skin lesions (erythema nodosum, pyoderma gangrenosum), and liver disease (primary sclerosing cholangitis — more strongly associated with UC).

Ask about NSAIDs (can precipitate flares), recent antibiotics or infections (especially C. difficile), smoking status, family history of IBD and colorectal cancer, prior treatments and responses, vaccination status, and pregnancy or fertility concerns.

Investigations in general practice

eTG Gastrointestinal IBD and GESA IBD shared care guidelines recommend the following GP-led workup:

• FBC, CRP, ESR, albumin — inflammation, anaemia, nutritional status
• Iron studies, B12, vitamin D — deficiencies common in active disease
• LFTs — screen for associated autoimmune hepatitis and PSC
• Faecal calprotectin — the key non-invasive triage test; less than 50 µg/g is normal (likely IBS), 50–250 indeterminate, >250 suggests active mucosal inflammation and requires gastroenterology referral
• Stool MCS, C. difficile PCR, ova and parasites — exclude infection before assuming IBD flare
• Coeliac serology (anti-tTG IgA + total IgA) — important differential
• Colonoscopy with biopsy — gold standard for diagnosis, extent, and dysplasia surveillance; initiated by gastroenterology

Red-flag features requiring emergency referral

• Acute severe colitis (Truelove-Witts criteria) — bloody diarrhoea ≥6 times per day plus any of: tachycardia, fever, anaemia, hypoalbuminaemia, elevated CRP/ESR → emergency department for IV methylprednisolone; rescue infliximab or ciclosporin by day 3 if no response; colectomy if unresponsive
• Toxic megacolon — colonic dilatation >6 cm on imaging plus systemic toxicity; immediate surgical consultation
• Bowel obstruction — in Crohn’s disease with strictures
• Perianal sepsis — abscess or complex fistula requiring drainage
• Severe uveitis — urgent ophthalmology

B. Treatment — from 5-ASA to biologics

Ulcerative colitis treatment hierarchy

For mild-to-moderate UC, eTG and AMH recommend:

• 5-ASA (mesalazine) oral 2.4–4.8 g daily + topical (suppository for proctitis, enema for left-sided disease) — achieves remission in ~80% of mild-moderate UC
• Oral prednisolone 40–60 mg daily tapering over 8–12 weeks if 5-ASA is inadequate
• Maintenance with 5-ASA long-term; thiopurine (azathioprine, mercaptopurine) for steroid-dependent or frequent relapsers

For moderate-to-severe UC or 5-ASA failure, biologic therapies are used — initiated by gastroenterology with PBS Authority:

• Anti-TNF (infliximab, adalimumab, golimumab)
• Vedolizumab (gut-selective integrin blocker — preferred in infection-prone or elderly patients)
• Ustekinumab (IL-12/23 blockade)
• Risankizumab (Skyrizi) and mirikizumab (Omvoh) (anti-IL-23 p19 subunit) — now PBS-listed under Section 100 Authority; increasingly first-line biologic choices per 2024–25 evidence
• JAK inhibitors — upadacitinib (Rinvoq) and tofacitinib (Xeljanz); oral, PBS Authority; carry a boxed warning for VTE, major cardiovascular events, and malignancy risk — typically reserved for post-anti-TNF failure

Crohn’s disease treatment

Mild ileocolonic CD responds to budesonide (controlled-release, ileum-targeted) or oral prednisolone for more extensive disease. Exclusive enteral nutrition is first-line induction for paediatric Crohn’s, comparable to steroids and growth-preserving.

Moderate-to-severe CD is managed with the same biologic menu as UC. The SONIC trial (Colombel, NEJM 2010) demonstrated that combination therapy (infliximab + azathioprine) is superior to either alone in CD; combination therapy is preferred for moderate-to-severe disease balanced against lymphoma risk (particularly in young males).

Methotrexate remains an option as immunomodulator for CD when thiopurines are not tolerated. It is teratogenic — strict contraception required and must be ceased at least three months before any attempt to conceive.

C. GP shared-care duties

Vaccinations

IBD patients on immunosuppression have specific vaccination needs, managed by the GP. Per GESA and eTG:

• Pre-biologic/JAK screen — hepatitis B (HBsAg, HBcAb), hepatitis C, HIV, latent TB (IGRA/Quantiferon + CXR), varicella/MMR serology; vaccinate non-immune patients before starting immunosuppression
• Live vaccines (MMR, varicella/VZV, BCG, oral typhoid, yellow fever) are contraindicated on biologic or JAK inhibitor therapy
• Inactivated vaccines safe on biologics/JAK — annual influenza, COVID, pneumococcal (Prevenar 20 single dose), shingles (Shingrix — non-live, safe on biologics), hepatitis B (high-dose if non-immune), HPV

Bone health

Frequent or prolonged corticosteroid use drives osteoporosis risk. Per RACGP guidance:

• DXA scan at diagnosis and when steroid use exceeds 3 months at ≥7.5 mg prednisolone equivalent per day
• Calcium 1000–1300 mg/day dietary; vitamin D 1000–2000 IU/day if deficient
• Bisphosphonate per Healthy Bones Australia and RACGP 2024 osteoporosis guideline criteria

Nutritional deficiencies and mental health

Iron deficiency anaemia is common — oral iron is often poorly tolerated in active IBD; intravenous iron (ferric carboxymaltose or iron sucrose) is preferred. B12 deficiency is a specific risk in Crohn’s disease affecting the terminal ileum (where B12 is absorbed). Vitamin D deficiency is nearly universal in active disease.

Anxiety and depression affect approximately 30% of IBD patients. General practice is well placed to screen and initiate psychological support via Mental Health Care Plan (items 2715/2717) with referral to psychologist through Better Access.

D. Australian operations

MBS items in general practice:

Standard consultations (items 23, 36, 44) cover routine shared-care reviews. The GP Chronic Condition Management Plan (GPCCMP — items 965/967, from 1 July 2025) qualifies IBD patients for Allied Health referrals: dietitian, psychologist, IBD-specialist nurse.

Faecal calprotectin (item 66290) is Medicare-rebatable with Authority Required. Colonoscopy (items in the 32090 range) for diagnosis and surveillance is initiated by gastroenterology. DXA (item 12306) for steroid-induced or chronic disease qualifies under Medicare.

PBS authority for IBD medications:

• 5-ASA (mesalazine, sulfasalazine) — Authority Required for IBD
• Thiopurines (azathioprine, mercaptopurine) — Authority Required for IBD; TPMT/NUDT15 testing (Medicare-rebatable) required before initiation
• Methotrexate — Authority Required for IBD
• Anti-TNF, vedolizumab, ustekinumab, risankizumab, mirikizumab, tofacitinib, upadacitinib, ozanimod — Section 100 Highly Specialised Drugs; specialist initiation

Telehealth: appropriate for stable shared-care reviews of established IBD patients meeting the 12-month existing-relationship rule.

E. Special populations

Pregnancy. Pre-conception remission optimises outcomes. Safe medications through pregnancy include 5-ASA, sulfasalazine (with folate 5 mg), azathioprine, infliximab, adalimumab, certolizumab (preferred — lowest placental transfer), vedolizumab, and ustekinumab. Methotrexate and JAK inhibitors are contraindicated. Infants exposed to biologics in utero should not receive live vaccines for the first six months of life.

Paediatric IBD. Exclusive enteral nutrition is first-line induction for paediatric Crohn’s disease. Paediatric gastroenterology specialist input is essential; growth, puberty, and educational impacts require dedicated attention.

Older adults. Vedolizumab is preferred as a biologic in older patients because its gut-selective mechanism carries lower systemic infection risk than anti-TNF agents. JAK inhibitors have heightened cardiovascular and thrombotic risk in older patients who are also smokers.

Young adult males on combination therapy (anti-TNF + thiopurine). Hepatosplenic T-cell lymphoma (HSTCL), though rare, is disproportionately reported in young males on combination immunosuppression. Risk-benefit discussion and documentation is important.

When to escalate

Refer to the emergency department immediately for acute severe colitis meeting Truelove-Witts criteria, suspected toxic megacolon, bowel obstruction, severe perianal sepsis or abscess, or severe extraintestinal manifestation (uveitis, PSC complication, thrombosis).

Same-week gastroenterology referral for: new diagnosis of IBD, flare unresponsive to GP-level therapy, new perianal symptoms, suspected pregnancy complication, C. difficile superinfection not resolving.

Routine gastroenterology referral for: annual review, cancer surveillance colonoscopy, medication adjustment, pre-biologic screening review.

What this article is and is not

This is general health information drawing on eTG, AMH, RACGP, GESA, and Crohn’s & Colitis Australia guidance. It is not personal medical advice and does not create a doctor–patient relationship. Specific treatment decisions — particularly around biologic initiation, vaccination timing, and pregnancy planning — are made with your gastroenterologist and GP.

AU consumer resources: Crohn’s & Colitis Australia, HealthDirect — IBD, Better Health Channel — IBD.

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Sources cited

1. GESA — IBD shared care guidelines
2. Crohn’s & Colitis Australia
3. Therapeutic Guidelines (eTG) — Gastrointestinal: IBD
4. Australian Medicines Handbook
5. RACGP — IBD in general practice
6. PBS — IBD biologic listings
7. HealthDirect — Inflammatory bowel disease
8. Better Health Channel — IBD
9. Cochrane — Biologics for IBD
10. Colombel et al. SONIC trial — NEJM 2010