Induction of mucosal healing by biologics is topographically comparable in proximal and distal small bowel Crohn's disease.

Two current US guidelines govern Crohn's disease and should be read together. ACG 2025 (Lichtenstein et al.) remains the reference for diagnosis, mild-to-moderate disease, perianal, postoperative and abscess management. DIAGNOSIS: fecal calprotectin (>50-100 μg/g) separates inflammatory from noninflammatory disease of the colon. Workup is ileocolonoscopy with biopsies, including uninvolved mucosa, plus small-bowel imaging. CTE and MRE are comparable; prefer MRE in patients <35 y and when serial exams are likely. Intestinal ultrasound is an ungraded adjunct. Do routine CRC surveillance in Crohn's colitis. MILD-TO-MODERATE: recommend against oral mesalamine; sulfasalazine only for symptomatic mild colonic CD; ileal-release budesonide 9 mg for induction in ileocecal disease but not for maintenance. MODERATE-TO-SEVERE (AGA Living Guideline, Scott et al., Gastroenterology 2025;169(7):1397-1448, 16 recommendations: 1 strong, 9 conditional, 6 knowledge gaps; updated quarterly, adult outpatients only): RECOMMEND infliximab, adalimumab, ustekinumab, risankizumab, mirikizumab, guselkumab or upadacitinib over no treatment; SUGGEST certolizumab pegol or vedolizumab over no treatment. Advanced-therapy-naive: suggest higher-efficacy agents (infliximab, adalimumab, vedolizumab, ustekinumab, risankizumab, mirikizumab, guselkumab) over lower-efficacy ones (certolizumab pegol, upadacitinib). Prior advanced-therapy (especially anti-TNF) exposure: suggest higher- or intermediate-efficacy agents (adalimumab, risankizumab, guselkumab, upadacitinib; ustekinumab, mirikizumab) over lower-efficacy ones (vedolizumab, certolizumab pegol). Suggest against thiopurine monotherapy for induction; suggest it for maintenance of remission. Suggest SC/IM methotrexate monotherapy; suggest against oral methotrexate. In thiopurine-naive patients starting infliximab, suggest infliximab + thiopurine over infliximab alone. No recommendation on IFX + MTX, adalimumab + immunomodulator, or non-TNF biologic + immunomodulator. After ≥6 months of steroid-free remission on anti-TNF + immunomodulator, suggest withdrawing the immunomodulator and suggest against withdrawing the anti-TNF. SUGGEST upfront advanced therapy over step-up therapy (corticosteroids and/or immunomodulator first). No recommendation on treating to endoscopic vs symptomatic remission. The ACG 2025 moderate-to-severe recommendations (anti-TNF, IFX + thiopurine combination and IL-12/23/IL-23 agents, each strong/moderate; upadacitinib after anti-TNF exposure; steroids for short-term induction only; TPMT/NUDT15 testing before thiopurines) still stand alongside AGA. ACG perianal (infliximab first; drain abscesses and place setons before escalating), postoperative (endoscopy at 6-12 months; anti-TNF strong, vedolizumab conditional in high-risk patients) and intra-abdominal abscess (>2 cm: antibiotics plus drainage, hold immunosuppression) positions are unchanged. THERAPEUTIC ENDOSCOPY (AGA Clinical Practice Update, CGH 2026; details below come from AGA news coverage, not the full text, and are ungraded advice): get cross-sectional imaging before the procedure. Endoscopic balloon dilation is first-line for short strictures (about ≤4-5 cm) with few risk factors (fistula, prestenotic dilation >5 cm, high CRP, prior anti-TNF). Longer or multiple strictures, or ≥3 risk factors, favor surgery.