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Overview and Recommendations
Background
- •Recognize IBD as a heterogeneous group of idiopathic inflammatory conditions, primarily and , driven by a complex interplay of genetic susceptibility, environmental triggers, and dysregulated immune responses. While CD is characterized by 'skip lesions' and transmural involvement, UC typically presents with continuous mucosal inflammation starting from the rectum.
- •Identify the global epidemiological shift where IBD prevalence is increasing worldwide, now affecting over 5 million individuals with UC alone. While traditionally a disease of young adults, the 'elderly-onset' population (≥60 years) is the fastest-growing demographic, presenting unique challenges due to comorbidities and increased frailty.
- •Understand the systemic nature of IBD, which extends beyond the gut to include extraintestinal manifestations (EIMs) such as , uveitis, and primary sclerosing cholangitis. IBD is also associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD) and venous thromboembolism (VTE), particularly during active flares.
- •Note the importance of phenotypic variants such as perianal fistulizing Crohn's disease (pfCD) and acute severe ulcerative colitis (ASUC). ASUC is a life-threatening emergency requiring rapid hospitalization and intensive medical rescue to avoid emergency colectomy.
- •Consider the role of genetic drivers like the NOD2 gene, which is found in approximately 40% of Caucasian CD patients and is linked to related multisystem disorders such as Yao syndrome (YAOS) and Blau syndrome.
Evaluation
- •Suspect IBD in patients presenting with chronic diarrhea (especially nocturnal), hematochezia, abdominal pain, weight loss, or unexplained growth failure in pediatric populations. Always ask about a family history of IBD and the presence of extraintestinal symptoms like joint pain or skin rashes.
- •Obtain baseline inflammatory biomarkers, specifically C-reactive protein (CRP) and fecal calprotectin. Fecal calprotectin is highly sensitive for intestinal inflammation and is used to differentiate IBD from functional disorders like (IBS).
- •Order a complete blood count (CBC) and iron studies to screen for anemia, which is the most common systemic complication. Also, check albumin levels as hypoalbuminemia can indicate severe disease and predict poor response to certain biologics like infliximab.
- •Perform a thorough physical examination, including a digital rectal exam and inspection of the perianal area for skin tags, fistulas, or abscesses, which are highly suggestive of Crohn's disease.
- •Utilize (IUS) as a first-line, non-invasive tool to assess bowel wall thickness (BWT). A BWT > 3 mm is a key indicator of active inflammation and can be used for longitudinal monitoring without radiation exposure.
- •Order Magnetic Resonance Enterography (MRE) or CT Enterography (CTE) to evaluate for small bowel involvement, strictures, or penetrating disease (fistulas/abscesses) that cannot be reached by standard endoscopy.
- •Perform a with multiple biopsies from both inflamed and non-inflamed segments. Histological features such as crypt abscesses in UC or non-caseating granulomas in CD are diagnostic hallmarks.
- •Classify the disease using the Montreal Classification for adults or the Paris Classification for pediatric patients to standardize the description of disease location, behavior, and age at onset.
- •Rule out infectious mimics, particularly Clostridioides difficile, which has a high prevalence (up to 28%) in IBD patients on biologics and can trigger or exacerbate flares.
- •Screen for baseline sarcopenia and nutritional deficiencies using EWGSOP2 criteria, as muscle loss is a significant predictor of poor outcomes and incident IBD.
- •Evaluate for perianal disease using pelvic MRI, which is the reference standard for classifying complex branching fistulas, or transperineal ultrasonography (TPUS) as a non-invasive alternative.
- •Assess for psychological comorbidities, including anxiety and depression, which are highly prevalent and closely correlated with disease activity, especially in adolescents.
Management
- •Adopt a 'treat-to-target' strategy aiming for transmural healing (TMH), defined by the normalization of bowel wall thickness on ultrasound, rather than just symptomatic relief. TMH is associated with superior long-term outcomes and lower surgery rates.
- •Induce remission in moderate-to-severe UC using Guselkumab 200 mg or 400 mg IV at weeks 0, 4, and 8, or initiate anti-TNF therapy such as Infliximab 5 mg/kg IV.
- •Manage Acute Severe Ulcerative Colitis (ASUC) with inpatient IV Methylprednisolone 60 mg/day. If no response is seen by day 3 (e.g., PUCAI score > 45 in children), initiate rescue therapy with Infliximab 5 mg/kg or Cyclosporine.
- •Utilize personalized dosing models (e.g., iDose) for Infliximab in ASUC to account for high drug clearance in patients with high inflammatory burdens, aiming to maximize colectomy-free survival.
- •Administer Exclusive Enteral Nutrition (EEN) as first-line induction therapy for pediatric Crohn's disease. Provide 100% of daily caloric requirements via liquid formula for 6 to 8 weeks to induce mucosal healing and avoid steroid toxicity.
- •Transition to maintenance therapy with Subcutaneous (SC) Infliximab 120 mg every 2 weeks, which often achieves higher colonic tissue concentrations than IV administration.
- •Consider Ustekinumab for Crohn's disease, induced with a weight-tiered IV dose (e.g., 6 mg/kg for patients ≥40 kg) and maintained with 90 mg SC every 8 weeks, especially in patients with symptomatic ileal strictures.
- •Employ small molecule JAK inhibitors like Upadacitinib 15-30 mg daily or Filgotinib 200 mg daily for refractory UC cases that have failed biologic therapy.
- •Monitor therapy using Therapeutic Drug Monitoring (TDM) to assess drug trough levels and the development of anti-drug antibodies (ADAs), particularly when clinical response is lost.
- •Address iron deficiency anemia with IV Iron (e.g., Ferric Carboxymaltose 1000 mg) rather than oral iron during active flares to ensure better absorption and avoid GI irritation.
- •Implement bone protection for patients on prolonged corticosteroids, including Calcium 1000–1200 mg/day and Vitamin D 800–1000 IU/day, to mitigate the risk of osteoporosis and fractures.
- •Refer for surgical consultation early in cases of uncomplicated ileocaecal CD; laparoscopic ileocaecal resection is a valid alternative to Infliximab with high rates of long-term therapy-free remission.
- •Manage fibrostenotic strictures with Endoscopic Balloon Dilation (EBD) or Endoscopic Stricturotomy (ESt) for short (< 5 cm) accessible lesions before considering surgical resection.
- •Maintain maintenance therapy throughout pregnancy to prevent flares, as active disease is the greatest risk to the fetus. Anti-TNFs, Vedolizumab, and Ustekinumab are generally considered safe during gestation.
- •Avoid live vaccines in patients on biologics or immunosuppressants. Ensure all age-appropriate vaccinations and screenings (e.g., TB, Hepatitis B/C) are completed prior to starting advanced therapies.
Board Review — High Yield
- •ASCA vs pANCA — Anti-Saccharomyces cerevisiae antibodies (ASCA) are associated with Crohn's; pANCA is more common in Ulcerative Colitis.
- •Transmural vs Mucosal — Crohn's involves the full thickness of the bowel wall (transmural); UC is limited to the mucosa and submucosa.
- •Skip Lesions — Characteristic of Crohn's disease, where areas of inflammation are separated by normal-appearing mucosa.
- •Crypt Abscesses — A classic histological finding in Ulcerative Colitis representing neutrophils within the colonic crypts.
- •Toxic Megacolon — A surgical emergency defined by colonic dilation > 6 cm associated with systemic toxicity.
- •Exclusive Enteral Nutrition (EEN) — The preferred first-line induction therapy for pediatric Crohn's disease, superior to steroids for mucosal healing.
- •Rutgeerts Score — Used to assess the risk of endoscopic recurrence in Crohn's disease after ileocaecal resection.
- •NOD2/CARD15 — The first gene associated with Crohn's disease susceptibility, particularly ileal involvement.
Deep Dive — Evidence Details
Definition, Synonyms, and Classification
- ▸IBD is the umbrella term for ulcerative colitis and Crohn’s disease; it is not interchangeable with either disease-specific diagnosis. [116]
- ▸IBD-U is used when UC and CD cannot be reliably distinguished and may remain stable or be revised during longitudinal follow-up. [119]
- ▸Crohn’s disease is classified by location and behavior, including **stricturing** and **penetrating** phenotypes and perianal fistulizing disease. [2][117][128]
- ▸The Montreal system uses **A1, A2, and A3** age-at-diagnosis categories, while the Vienna framework commonly uses a **40-year** threshold. [121]
- ▸Anti-integrin αvβ6 antibodies, microbiome profiles, transcriptomic signatures, and spectroscopy are supportive or investigational features, not stand-alone replacements for clinicopathologic classification. [1][116][117][122][125]
Definition
Inflammatory bowel disease (IBD) is an umbrella term for chronic, immune-mediated inflammatory disorders of the gastrointestinal tract, principally ulcerative colitis (UC) and Crohn’s disease (CD). [116] UC is characterized primarily by mucosal inflammation and epithelial injury, whereas CD may involve any gastrointestinal segment and is clinically distinguished by substantial heterogeneity in anatomic location and disease behavior. [1][117] The term “IBD” should therefore not be used as a synonym for UC or CD; it identifies the disease family, while UC and CD identify the principal disease entities within that family. [116]
“Inflammatory bowel diseases” is the plural form of IBD. Common disease-specific abbreviations are UC for ulcerative colitis and CD for Crohn’s disease. [116] When the available clinical, endoscopic, radiologic, and histologic findings do not permit a reliable distinction between UC and CD, the appropriate classification is IBD unclassified (IBD-U). [119]C IBD-U is a clinical classification rather than a separate biologic disease, and longitudinal observation may permit later reclassification, although classification may remain stable for prolonged periods. [119]C
An IBD-like phenotype may also occur in patients with inborn errors of immunity, such as SOCS1 haploinsufficiency; this terminology indicates an IBD-like inflammatory presentation associated with an underlying monogenic immune disorder and should not automatically be equated with conventional idiopathic IBD. [131]C
Core disease classification
IBD classification is multidimensional. It includes disease type, anatomic distribution, age at diagnosis, inflammatory activity, behavior, complications, and histopathologic or molecular features. [1][117][119]C[121][118] CD is commonly described according to location—ileal, colonic, ileocolonic, or upper-gastrointestinal involvement—and according to behavior, including inflammatory, stricturing, and penetrating phenotypes. [117][121] Disease location is clinically relevant because systematic evidence identifies location-associated differences in gut microbiota and metabolite profiles, particularly in ileal CD. [117]
Stricturing CD is defined clinically by the presence of intestinal narrowing and is a major behavioral phenotype; strictures may require medical, endoscopic, or surgical management. [128] Penetrating CD includes fistulizing disease, and perianal CD may manifest with fistulas or abscesses. [2] Perianal fistulas can be further characterized anatomically using classification systems such as Park’s classification, which is used to describe fistula morphology and complexity. [129]
Age-at-diagnosis classifications include the Vienna and Montreal systems. The Montreal framework categorizes age at diagnosis into A1, A2, and A3 groups, while the Vienna framework commonly contrasts diagnosis before versus after 40 years; these systems are used to standardize phenotype description and to evaluate associations with outcomes. [121] In a surgical cohort, age-based Vienna and Montreal categories did not necessarily predict postoperative outcomes after ileocecal resection, illustrating that classification variables are descriptive and may not independently determine prognosis. [121]
UC is classified by the extent of colonic involvement and by activity and severity. Its pathobiology includes interacting epithelial, stromal, and immune-cell compartments, and single-cell and spatial transcriptomic studies further subdivide UC according to cellular states, tissue niches, and cell–cell interactions. [1] Histopathologic classification is also relevant in CD, in which conventional assessment may be subjective and disease-associated abnormalities include crypt and inflammatory-cell changes that can be quantitatively evaluated using digital methods. [118]
Related and complication-based classifications
Neoplastic lesions in UC require distinction between colitis-associated neoplasia and sporadic neoplasia. Lesions arising in colitis-affected areas may be operationally classified as confirmed or probable UC-associated neoplasia, whereas lesions in colitis-unaffected areas may be classified as sporadic neoplasia. [120] This distinction is based on lesion context and, in the cited study, morphology and immunostaining patterns rather than on the general label of UC alone. [120]
IBD classification should not rely on a single biomarker. Anti-integrin αvβ6 IgG, previously associated with adult UC, was also detected in a substantial minority of children with CD, particularly in association with colonic inflammation; therefore, its presence does not reliably define UC in pediatric disease. [122] Similarly, serum spectroscopy and other emerging molecular approaches may support CD discrimination but remain investigational rather than replacement classifications. [125]C
Phenotypic context and terminology boundaries
Microbiome and metabolome alterations are consistently associated with IBD, with reduced microbial diversity the most reproducible broad finding across heterogeneous studies, although specific alterations vary by disease and location. [116][117] Gut fungal communities and systemic adaptive immune responses to fungal antigens have also been investigated, particularly in CD, but these findings describe disease mechanisms or biomarkers rather than formal diagnostic categories. [17]D Associations with oral-health problems, micronutrient abnormalities, low bone mineral density, medication pharmacogenetics, and postoperative biologic management describe comorbidity, nutritional, therapeutic, or prognostic dimensions of IBD and do not constitute additional IBD subtypes. [6][126][130][127][123]
Accordingly, the preferred classification sequence is: IBD type (UC, CD, or IBD-U); for CD, location and behavior; for UC, extent and activity; and for either disease, complications, histology, extraintestinal manifestations, and relevant molecular or immune features. [1][117][118][119]C[121]
| Term or axis | Meaning | Key distinction |
|---|---|---|
| IBD | Umbrella disease family comprising UC and CD | Not a disease-specific diagnosis [116] |
| UC | Colonic inflammatory disease with mucosal inflammation and epithelial injury | Classified by extent, activity, severity, histology, and complications [1] |
| CD | Gastrointestinal inflammatory disease with location and behavioral heterogeneity | Classified by location, inflammatory/stricturing/penetrating behavior, and complications [117][121] |
| IBD-U | IBD in which UC versus CD cannot yet be established | May be reclassified longitudinally [119]C |
| Perianal CD | Fistulizing or abscess-forming perianal manifestation of CD | Fistula anatomy may be described using Park’s classification [2][129] |
| UC-associated neoplasia | Neoplasia arising in colitis-affected areas | Distinguished from sporadic neoplasia in unaffected areas [120] |
Epidemiology and Risk Factors
- ▸Recent evidence supports heterogeneity in IBD risk and outcomes according to disease phenotype, severity, age, comorbidity, treatment exposure, and disease duration. [138][143]
- ▸Pulmonary disease is an important comorbidity domain, with evidence addressing both obstructive lung disease and interstitial lung disease. [133][144]
- ▸Prenatal acid-suppressive medication exposure has been evaluated as a potential early-life risk factor for incident childhood IBD, but observational associations do not establish causation. [145]
- ▸Frailty is operationalised using Fried-derived criteria; **≥3 criteria** defines frailty and **1–2 criteria** an intermediate state. [151]
- ▸Anemia is reported more frequently in CD than UC and may reflect inflammation, blood loss, impaired absorption, and microbiome-mediated iron competition. [136]
- ▸Advanced therapies and anti-TNF exposure are associated with measurable infectious, psychiatric, and immunogenicity risks in observational cohorts. [139][142][146]
- ▸Postoperative CD complications occur in a reported range of **20%–50%**, with infectious complications, abscess, and anastomotic leakage among the major outcomes. [134]
Scope and epidemiologic context
Inflammatory bowel disease (IBD) comprises Crohn disease (CD) and ulcerative colitis (UC), chronic inflammatory disorders with clinically important intestinal and extraintestinal consequences. Recent evidence continues to document substantial heterogeneity by phenotype, age, geography, comorbidity, treatment exposure, and disease duration. A Korean prospective multicentre inception cohort specifically examined long-term outcomes in 353 patients with newly diagnosed moderate-to-severe UC enrolled between August 2014 and February 2017, with a median follow-up of 4.9 years (interquartile range, 2.1–5.0 years). [138]C The study was designed to identify factors associated with a disabling disease course, supporting the importance of prospective, disease-severity-specific epidemiology rather than reliance on prevalence estimates alone. [138]C
A Danish nationwide cohort identified 53,591 patients with IBD and 267,955 age- and sex-matched controls from registry data spanning 1978–2022 to evaluate incident interstitial lung disease (ILD). [144] This design reflects the population burden of extraintestinal disease and permits assessment of age, sex, education, and comorbidity as potential confounders through adjustment for these variables and the Charlson Comorbidity Index. [144] Respiratory comorbidity is also relevant more broadly: a systematic review and meta-analysis evaluated the bidirectional association between IBD and obstructive lung diseases, including chronic obstructive pulmonary disease, asthma, and bronchiectasis, using observational studies available through 30 June 2025. [133]
Demographic and early-life factors
Age at assessment is clinically relevant across the IBD spectrum. The RELIEVE UCCD phase 2b trial enrolled adults aged 18–75 years with moderately to severely active UC, including individuals with inadequate response, loss of response, or intolerance to previous conventional or advanced therapies. [132] This population illustrates that treatment-refractory disease occurs across a broad adult age range, although a therapeutic trial should not be interpreted as a population-incidence study. [132]
Potential prenatal environmental influences have been examined in a nationwide South Korean mother–child cohort. The study assessed prenatal exposure to proton-pump inhibitors and H2-receptor antagonists among mother–child pairs identified from 2009–2017, with follow-up through 31 December 2023, and evaluated incident IBD in offspring, including CD and UC. [145] Because this was an observational cohort using national health-insurance data, the findings address association rather than proof of causation. [145]
Pulmonary, metabolic, and systemic comorbidity
IBD may coexist with or precede pulmonary disease. The systematic review by Ding and colleagues evaluated COPD, asthma, and bronchiectasis in relation to both CD and UC and explicitly examined whether the association was bidirectional. [133] The Danish registry study further focused on ILD risk and survival among patients with IBD, indicating that pulmonary disease is an important comorbidity for epidemiologic surveillance and outcome assessment. [144]
Cardiometabolic risk is increasingly relevant in IBD populations. A real-world cohort of adults with CD or UC followed patients from 2010–2024 and assessed temporal trends in metabolic syndrome (MetS), cardiometabolic disease, and hepatic, renal, cardiovascular, and IBD-related outcomes. [143] The study compared patients with IBD and MetS, IBD without MetS, and MetS without IBD using propensity-score matching, reflecting the need to account for metabolic comorbidity when evaluating IBD outcomes. [143]
Frailty is another clinically relevant risk phenotype. In a prospective single-centre cohort of adults hospitalised with active IBD who required initiation of a biologic or small molecule, frailty was measured using a modified Fried index. Three or more criteria—shrinking, exhaustion, weakness, slowness, or low physical activity—defined frailty, whereas one to two criteria defined an intermediate state. [151]C
Disease- and treatment-related risk factors
Anemia is a frequent systemic complication of IBD and has been reported more often in CD than UC. [136] The systematic review attributed this difference to interacting mechanisms that include chronic inflammation, impaired iron absorption, intestinal blood loss, and microbiome-related effects on iron availability; it highlighted increased siderophore-producing bacteria, particularly Enterobacteriaceae, as an emerging CD-associated mechanism. [136]
Treatment exposure is itself associated with important risks and may confound observational comparisons. In a 13-hospital common-data-model analysis, patients receiving advanced therapies had higher observed risks of tuberculosis (HR 2.86, 95% CI 1.77–4.63) and depression/anxiety (HR 1.58, 95% CI 1.15–2.16) than matched patients not receiving advanced therapy. [146] In a Middle Eastern cohort comprising 314 anti-TNF treatment courses in 248 patients, immunogenicity developed in 28.3% of courses over a median follow-up of 24.0 months; the study evaluated predictors and drug-level thresholds for loss of response. [139] In children aged 6–17 years, a nationwide claims-based cohort compared infection risk after new initiation of infliximab versus adalimumab using at least 180 days of prior continuous enrollment. [142]
Surgical and disease-course risk factors
Postoperative morbidity is substantial in CD surgery, with reported complication rates of 20%–50% in a systematic review; complications included surgical-site infection, intra-abdominal abscess, and anastomotic leakage. [134] A multicentre retrospective study evaluated residual ileocolic artery length after ileocolic resection as a surrogate for residual mesenteric burden and examined its relationship with postoperative endoscopic recurrence. [141] In paediatric IBD, an 18-year UK population-based cohort covering 2007–2024 evaluated anti-TNF exposure and abdominal surgery rates, including strictureplasty, resection, and primary stoma formation. [140] These studies support disease severity, anatomy, prior treatment, and perioperative factors as important components of risk stratification, while their observational designs limit causal inference. [134][140][141]
Other uncommon but high-risk contexts include intestinal ulceration with pancytopenia and coexisting myelodysplastic syndrome or aplastic anemia, for which pooled individual-patient data were used to examine mortality and prognostic factors. [137] Cancer history also affects the epidemiology and management of IBD: a Danish nationwide cohort included 59,494 patients, comprising 20,551 CD cases and 38,943 UC cases, and compared treatment and surgery among those with prior or coexisting cancer versus those without cancer. [148] In endemic Mediterranean settings, symptomatic leishmaniasis has been investigated as an opportunistic infection among biologic-treated IBD patients using a population-based cohort and multicentre case-control design covering 2015–2022. [149]C Finally, anxiety and depression have been studied as potential perioperative risk factors in major colorectal surgery, while a two-centre prospective case-control study evaluated their relationship with 90-day postoperative complications. [150]C
| Domain | Population or design | Key evidence |
|---|---|---|
| UC disease course | Korean inception cohort; 353 patients; median follow-up 4.9 years | Evaluated disabling disease trajectories in moderate-to-severe UC. [138]C |
| Pulmonary disease | Systematic review; studies through 30 June 2025 | Examined bidirectional IBD associations with COPD, asthma, and bronchiectasis. [133] |
| ILD | Danish nationwide cohort; 53,591 IBD patients and 267,955 controls | Assessed ILD risk and subsequent mortality. [144] |
| Prenatal exposure | South Korean mother–child cohort; 2009–2017 births/data, follow-up through 2023 | Evaluated prenatal PPI/H2RA exposure and childhood IBD. [145] |
| Frailty | Prospective cohort of hospitalised adults with active IBD | ≥3 Fried-derived criteria defined frailty. [151]C |
| Surgical risk | Systematic review of CD surgery | Postoperative complication rates reported at 20%–50%. [134] |
Management of Inflammatory Bowel Disease
- ▸Targeting transmural healing (TMH) via intestinal ultrasound is superior to targeting clinical symptoms alone for preventing long-term complications.
- ▸Subcutaneous Infliximab provides higher colonic tissue concentrations than IV administration and may overcome low-titer anti-drug antibodies.
- ▸Laparoscopic resection is a highly effective first-line alternative to biologics for localized, uncomplicated ileocaecal Crohn's disease.
The of Inflammatory Bowel Disease (IBD) has evolved from symptom-based control to a "treat-to-target" paradigm focusing on objective markers of inflammation. This approach aims to prevent structural bowel damage and reduce the long-term need for surgery [54]. Management strategies differ significantly between (CD) and (UC), though both rely on a tiered approach of induction and maintenance therapy using biologics and small molecules.
Step 1: Initial Assessment and Severity Classification
Clinicians must first classify disease activity to determine the appropriate setting for care. For UC, the modified Mayo score ≥11 or the presence of systemic symptoms (tachycardia, fever, anemia) indicates acute severe ulcerative colitis (ASUC), requiring immediate hospitalization [35]D[65]D. In pediatric patients, the presence of extraintestinal manifestations (EIMs) at diagnosis—found in 25% of CD and 14% of UC cases—is a strong predictor of a more severe disease course, including earlier steroid dependency and the need for biological therapy [58].
Initial assessment should include baseline biomarkers (CRP, fecal calprotectin) and, increasingly, (IUS). In pediatric CD, a bowel wall thickness (BWT) threshold measured via IUS can predict 1-year treatment response and remission [72]D. Patients with symptomatic ileal strictures or perianal abscesses require surgical consultation early in the assessment phase [56][67]D.
Step 2: Induction of Remission
Induction therapy aims to rapidly control inflammation. For moderate-to-severe UC, Guselkumab 200 mg or 400 mg IV at weeks 0, 4, and 8 has demonstrated significant molecular and cellular improvements in colonic tissue [49]. In ASUC, the standard of care remains IV corticosteroids (e.g., Methylprednisolone 60 mg/day); however, approximately 30-40% of patients fail to respond, necessitating rescue therapy [65]D.
Infliximab 5 mg/kg IV is the primary rescue agent for steroid-refractory ASUC. Because high inflammatory burden increases drug clearance, personalized dosing models (e.g., iDose) are used to adjust induction doses to maximize colectomy-free survival [19]D[55]. For pediatric CD, Ustekinumab is induced with a single weight-tiered IV dose (e.g., 6 mg/kg for those ≥40 kg) [50].
Step 3: Maintenance and Advanced Therapies
Once remission is achieved, therapy transitions to maintenance. Subcutaneous (SC) Infliximab (e.g., 120 mg every 2 weeks) is now preferred over IV administration in many cases because it achieves significantly higher colonic tissue drug concentrations [69]D. Interestingly, the development of anti-drug antibodies (ADAs) does not always correlate with clinical failure in SC Infliximab patients, suggesting that the higher trough levels may overcome low-titer immunogenicity [48].
For patients failing first-line biologics like , second-line options include switching to Infliximab or Ustekinumab 90 mg SC every 8 weeks [57]. In refractory UC, small molecule such as Upadacitinib 15 mg or 30 mg daily or Filgotinib 200 mg daily are effective [59]C[71]D. Filgotinib works by modulating the frequency and gene expression of circulating immune cell subsets, specifically targeting dysregulated T-cell populations [71]D.
Step 4: Monitoring and Titration to Target
Modern management targets transmural healing (TMH) rather than just mucosal healing. TMH, defined by the normalization of bowel wall thickness on ultrasound, is associated with a lower risk of long-term complications compared to clinical or endoscopic targets alone [54].
Monitoring should include:
- Therapeutic Drug Monitoring (TDM): Assessing drug clearance is vital, as high initial clearance of Infliximab is a major predictor of treatment failure and the development of ADAs [55].
- Non-invasive Imaging: IUS is a reliable tool for longitudinal monitoring, with early changes in BWT at week 4-8 predicting long-term remission [72]D.
- Biomarkers: Fecal aspirate transcriptomics is an emerging tool that may allow for the assessment of small bowel inflammation in asymptomatic CD patients without the need for full [70]D.
Step 5: Surgical Intervention and Long-term Outcomes
Surgery is not a failure of treatment but a strategic component of management. In uncomplicated ileocaecal CD, laparoscopic ileocaecal resection is a valid alternative to Infliximab, showing similar 10-year quality-of-life outcomes and high rates of long-term therapy-free remission [51]. For patients with ileal strictures, Ustekinumab may reduce the need for endoscopic balloon dilation (EBD) or surgery, though 25% of patients with symptomatic strictures will still require surgical intervention within one year [56].
In pregnant patients, advanced therapies (Anti-TNFs, Vedolizumab, Ustekinumab) are generally considered safe, with pooled prevalence rates for early pregnancy loss (8.2%) and congenital malformations (1.9%) being comparable to the general IBD population [22]. However, the method of delivery (Cesarean vs. vaginal) does not significantly impact the risk of severe maternal morbidity in IBD patients [66]D.
| Drug | Class | Dose (Maintenance) | Route | Key Consideration | Evidence Level |
|---|---|---|---|---|---|
| Infliximab | Anti-TNF | 120 mg every 2 weeks | SC | Higher tissue levels than IV [69]D | 1b |
| Ustekinumab | Anti-IL12/23 | 90 mg every 8-12 weeks | SC | Effective for ileal strictures [56] | 1b |
| Guselkumab | Anti-IL23p19 | 200-400 mg (Induction) | IV | Rapid molecular response in UC [49] | 1b |
| Upadacitinib | JAK Inhibitor | 15-30 mg daily | Oral | Requires VTE risk assessment [59]C | 4 |
| Filgotinib | JAK Inhibitor | 200 mg daily | Oral | Modulates T-cell gene expression [71]D | 5 |
Supportive Care and Complication Management
- ▸EEN has an established pediatric role and showed a pooled real-world adult remission rate of 66% in a 2026 meta-analysis.[160]
- ▸CDED, with or without PEN or EEN, is under active evaluation; current cited studies do not establish universal superiority of one dietary regimen.[152-154]
- ▸Evaluate anemia and fatigue systematically, including inflammatory, nutritional, hematologic, sleep, and psychological contributors.[136,165]
- ▸Differentiate inflammatory from fibrotic strictures because treatment pathways differ.[158,164]
- ▸Use the revised CT enterography prestenotic-dilatation threshold of ≥2.5 cm when assessing small-bowel strictures.[37]
- ▸Monitor patients receiving advanced therapies for tuberculosis and depression or anxiety.[146]
- ▸Maintain follow-up after pediatric perianal abscess drainage because subsequent CD diagnosis may occur.[67]
Nutritional support and dietary therapy
Exclusive enteral nutrition (EEN) remains an important nutritional induction strategy in Crohn’s disease (CD), particularly in children. A comparative analysis of prospective pediatric cohorts evaluated corticosteroids and EEN in newly diagnosed small-bowel CD involving the ileum, with sustained steroid-free remission at 1 year as the primary outcome and growth, time to first biologic, and time to luminal resection as secondary outcomes.[156] A systematic review and meta-analysis of adult randomized and real-world studies included 40 studies and 2,459 patients; the pooled clinical-remission rate in 23 real-world cohorts was 66%, although the abstract indicates that the adult evidence base remains less established than the pediatric evidence.[160]
The Crohn’s Disease Exclusion Diet (CDED) is being evaluated as an alternative or adjunct to EEN. In a prospective randomized pediatric trial, children aged 4–18 years with mild-to-moderate CD were assigned to CDED alone or CDED plus partial enteral nutrition (PEN), directly addressing whether CDED without PEN is effective.[153] In another randomized trial involving 54 children, CDED with either PEN or EEN was associated with longitudinal assessment of the tongue and buccal-gingival microbiome at baseline and multiple follow-up points through 52 weeks; no significant difference in primary or clinical outcomes was reported between groups, and both nutritional approaches were investigated for their effect on oral dysbiosis.[152] A pilot randomized trial in 46 post-surgical CD patients compared a modified Mediterranean diet supplemented with PEN for 4–5 weeks with EEN, using IBD quality of life as the primary outcome and nutritional status and disease-related characteristics as secondary outcomes.[154]C A systematic review and meta-analysis identified eight studies, including seven with 223 participants, evaluating Mediterranean-diet interventions for IBD remission and clinical response.[161]
Nutritional treatment should therefore be individualized, with monitoring of disease activity, tolerance, nutritional status, growth in children, and adherence. The available studies support nutritional therapy as an active management strategy, but the cited evidence does not establish one dietary regimen as universally superior.[152-154,156,160,161]
Anemia, fatigue, and hematologic complications
Anemia is a frequent systemic complication of IBD and is reported more often in CD than in ulcerative colitis (UC). Mechanisms discussed in a systematic review include chronic inflammation, impaired iron absorption, intestinal blood loss, and microbiome-mediated effects on iron availability; CD-associated dysbiosis may include increased siderophore-producing bacteria, particularly Enterobacteriaceae, which can compete with host iron-acquisition systems.[136] Fatigue remains a substantial problem in treated CD; an observational study specifically assessed psychological variables, insomnia, inflammatory-bowel-disease fatigue scores, stress, anxiety, depression, and laboratory findings as potential correlates.[165] These findings support routine assessment of fatigue, sleep, mood, inflammatory activity, and hematologic indices when symptoms persist.[136][165]
Intestinal ulceration accompanied by pancytopenia is uncommon but clinically serious. A pooled individual-patient systematic review examined cases occurring mainly in patients with IBD or intestinal Behçet disease and concurrent myelodysplastic syndrome or aplastic anemia, with clinical features, mortality, and prognostic factors as outcomes.[137] Ulceration with pancytopenia should therefore prompt urgent hematologic and gastrointestinal evaluation rather than being attributed automatically to uncomplicated IBD.[137]
Strictures and obstructive complications
Management depends on whether a stricture is predominantly inflammatory, fibrotic, or mixed. Inflammatory strictures may respond to anti-inflammatory treatment, whereas noninflammatory strictures may require endoscopic balloon dilation or surgical resection.[158]C Prospective MRI work evaluated T2* and diffusion-weighted intravoxel incoherent motion parameters against location-matched surgical histopathology for this distinction.[158]C A collagen-binding 68Ga-CBP8 PET/MR approach was also investigated for noninvasive detection of bowel collagen deposition and differentiation of inflammatory from fibrotic or mixed strictures.[164]C
CT enterography criteria have evolved: recent guidance lowered the prestenotic-dilatation threshold for identifying small-bowel stricture from >3 cm to ≥2.5 cm.[37]D This threshold change may increase the number of patients classified as having strictures, and the cited study evaluated whether the 2.5–3 cm and >3 cm categories differently stratify adverse outcomes.[37]D When endoscopic therapy is appropriate for lower-gastrointestinal strictures, an indirect meta-analysis synthesized endoscopic balloon dilation, stent placement, and stricturotomy across 39 studies involving 1,614 patients; the outcomes examined included technical and clinical success, adverse events, repeat procedures, and surgery.[162] Ustekinumab was evaluated retrospectively in 57 adults with imaging-confirmed symptomatic ileal stricturing CD, assessing endoscopic balloon dilation, surgery, composite intervention, recurrent obstruction, and treatment persistence.[56]
Perianal, esophageal, and treatment-related complications
Perianal abscess requires prompt surgical drainage. A retrospective pediatric cohort included 204 children aged 3–18 years undergoing drainage between 2005 and 2025 and examined subsequent CD diagnosis, with anemia and hypoalbuminemia defined using age-adjusted thresholds and serum albumin <3.5 g/dL, respectively.[67]D Children with apparently isolated perianal abscess should receive appropriate follow-up for later-recognized IBD.[67]D
Esophageal CD is rare and diagnostically challenging because symptoms are nonspecific. A systematic review identified 100 adult patients from 90 studies and characterized presentation, diagnostic pathways, and treatment approaches.[155] Persistent or unexplained upper-gastrointestinal symptoms in a patient with CD warrant consideration of esophageal involvement.[155]
Advanced therapies require ongoing safety surveillance. In a 13-hospital common-data-model analysis, patients receiving advanced therapies had higher observed risks of tuberculosis (HR 2.86, 95% CI 1.77–4.63) and depression/anxiety (HR 1.58, 95% CI 1.15–2.16) than matched patients not receiving advanced therapies.[146] These associations support tuberculosis risk assessment and monitoring of mental health during treatment.[146]
Imaging and individualized monitoring
Abbreviated MR enterography protocols that omit contrast and antiperistaltic agents were compared with conventional contrast-enhanced MRE for detection of disease activity and complications, including interreader agreement and concordance among abdominal radiologists.[163] Imaging selection should account for the clinical question, the need to characterize inflammation or fibrosis, radiation exposure, and local expertise.[37]D[158]C[163][164]C Machine-learning research using serum and stool metabolomics, lipidomics, and fecal microbiome data has also explored prediction of response to EEN in treatment-naive pediatric CD, but this approach remains investigational.[157]
| Clinical issue | Evidence-informed assessment focus |
|---|---|
| Nutritional compromise | Dietary tolerance, adherence, nutritional status, and pediatric growth during EEN, CDED, PEN, or Mediterranean-style interventions.[152-154,156,160,161] |
| Anemia and fatigue | Hemoglobin and other laboratory indices, inflammation, iron availability, blood loss, sleep, mood, anxiety, and depression.[136][165] |
| Suspected stricture | Cross-sectional imaging; assess prestenotic dilatation and inflammatory versus fibrotic phenotype.[37]D[158]C[163][164]C |
| Obstructive stricture | Consider endoscopic balloon dilation, stent placement, stricturotomy, surgery, or medical therapy according to anatomy and phenotype.[56][158]C[162] |
| Perianal abscess | Prompt drainage and follow-up for later CD features, anemia, or hypoalbuminemia.[67]D |
| Advanced therapy safety | Tuberculosis risk assessment and mental-health monitoring.[146] |
Special Populations
- ▸Maintain effective IBD therapy during pregnancy when required for disease control; medication cessation can increase relapse risk. [166][167][168][169][170][171][175]
- ▸Disease activity, rather than previous abdominal surgery alone, was associated with preterm birth in a prospective Crohn’s disease cohort. [172]
- ▸Advanced-therapy pregnancy evidence remains largely observational; a meta-analysis included 67 studies and 17,441 pregnancies and reported an early pregnancy-loss prevalence of 8.2%. [22]
- ▸Vedolizumab pregnancy evidence includes a prospective registry of 275 pregnancies and a separate systematic review/meta-analysis. [102][174]
- ▸Delivery decisions should account for active perianal disease and obstetric indications; the supplied abstracts do not provide complete numerical estimates for perineal injury or severe maternal morbidity. [66][177]
- ▸Pediatric acute severe ulcerative colitis requires proactive monitoring and timely medical or surgical intervention. [98]
- ▸Secondhand smoke avoidance is appropriate preventive counseling, while the supplied abstract does not report pooled effect estimates. [99]
Pregnancy: preconception and disease control
Pregnancy planning should be individualized and coordinated between gastroenterology, obstetrics, and, when appropriate, colorectal surgery. The 2025–2026 Global Consensus Statement was developed because inconsistent provider practices, limited pregnancy-specific evidence, medication concerns, and inadequate patient knowledge can influence pregnancy rates, treatment adherence, and outcomes. [166][167][168][169][170][171] Disease activity is a central modifiable determinant of pregnancy risk, and treatment decisions should prioritize sustained remission rather than unplanned medication withdrawal. [166][167][168][169][170][171]
Available prospective cohort evidence indicates that previous Crohn’s disease-related abdominal surgery, by itself, is not associated with adverse pregnancy, delivery, or neonatal outcomes. In the Pregnancy in Inflammatory Bowel Disease and Neonatal Outcomes cohort, 1,046 women with Crohn’s disease were evaluated, including 409 (39%) with previous surgery; those with prior surgery had more active disease, but multivariable analysis associated preterm birth with disease activity (OR 1.14, 95% CI 1.06–1.22) and ileal disease (OR 2.19, 95% CI 1.26–3.83), not previous surgery. [172] Preconception assessment should therefore focus on disease activity, phenotype, nutrition, prior operations, and medication optimization rather than treating prior surgery alone as an indication for pregnancy avoidance. [166][167][168][169][170][171][172]
Medication exposure during pregnancy
International guidance generally supports continuing effective immunomodulating therapy during pregnancy when needed to maintain disease control; stopping therapy may expose the parent and fetus to the risks of relapse. [166][167][168][169][170][171][175] Evidence for advanced therapies is expanding but remains predominantly observational, particularly for newer agents. [166][167][168][169][170][171][22]
A 2026 systematic review and meta-analysis included 67 observational studies and 17,441 pregnancies exposed to advanced therapies, with subgroup analyses by therapeutic class and assessment of maternal age, disease activity, disease duration, phenotype, and third-trimester exposure. [22] The pooled prevalence of early pregnancy loss was 8.2% (95% CI 6.2–10.8). [22] The evidence base included anti-TNF agents, vedolizumab, ustekinumab, and Janus kinase inhibitors, but the abstract emphasizes that evidence for newer agents remains more limited than for anti-TNF therapy. [22]
Vedolizumab-specific evidence includes a prospective North American pregnancy exposure registry of 275 women enrolled from 2015–2022: 99 were vedolizumab-exposed, 76 had IBD and were treated with another biologic, and 100 had no chronic health condition and were unexposed. [174] Participants and infants were followed through 1 year postpartum, with interviews, questionnaires, medical-record abstraction, and physical examination in a subset of infants. [174] A separate updated systematic review and meta-analysis evaluated live birth, preterm birth, early pregnancy loss, cesarean delivery, congenital malformations, small-for-gestational-age birth, and composite perinatal complications after vedolizumab exposure. [102]
Vaccination and infant immune considerations
The PETIT prospective cohort evaluated maternal Tdap vaccination and transplacental antibody transfer among pregnant women with IBD receiving different immunomodulating therapies; participants were recruited from 16 hospitals in the Netherlands between December 2018 and March 2023, and IgG concentrations against Tdap components were measured in mothers and infants at birth. [175] Available immunophenotyping data also evaluated maternal and infant immune-cell populations and cytokine responses during pregnancy, at delivery, postpartum, and at 6 weeks of infant age; the study’s reported conclusion was that IBD medications did not substantially impair innate or adaptive immunity in mothers or offspring. [176]C
Delivery and perineal disease
Delivery planning should be individualized according to obstetric factors, disease activity, prior surgery, and current or historical perianal disease. [166][167][168][169][170][171] A retrospective cohort study specifically assessed perineal injury among primiparous women with IBD without active perianal disease who had singleton, cephalic, term vaginal births; women with active perianal disease were excluded. [177] A population-based Ontario cohort evaluated severe maternal morbidity from 20 weeks’ gestation through 42 days postpartum and examined whether delivery method altered risk among individuals with Crohn’s disease or ulcerative colitis. [66]D The supplied evidence does not provide the numerical outcome estimates from that analysis. [66]D[177]
Children and adolescents
Acute severe colitis is an important pediatric emergency and requires standardized, proactive management with close monitoring, timely medical rescue, and early surgical involvement when indicated. [98] The updated ESPGHAN–ECCO consensus guideline addresses pediatric ulcerative colitis acute severe colitis using systematic evidence review and expert consensus. [98]
Tobacco and environmental exposures
A 2025 systematic review and meta-analysis evaluated passive smoking in relation to IBD incidence and outcomes for Crohn’s disease and ulcerative colitis using PRISMA and MOOSE methods and searches through May 2025. [99] Avoidance of secondhand smoke should be incorporated into preventive counseling, although the supplied abstract does not provide the pooled effect estimates. [99]
A nationwide South Korean mother–child cohort assessed whether prenatal exposure to proton-pump inhibitors or H2-receptor antagonists was associated with incident childhood IBD, including Crohn’s disease and ulcerative colitis, with follow-up through 31 December 2023. [145] The supplied abstract describes the study question and design but does not provide its effect estimates; therefore, it should not be used alone to establish causation or to recommend discontinuing clinically indicated acid-suppressive therapy. [145]
| Population or issue | Evidence and practical implication |
|---|---|
| Pregnancy and prior Crohn’s surgery | In 1,046 women, prior surgery was not independently associated with adverse pregnancy or neonatal outcomes; disease activity and ileal disease were associated with preterm birth. [172] |
| Advanced therapies | Meta-analysis: 67 observational studies and 17,441 pregnancies; early pregnancy loss 8.2% (95% CI 6.2–10.8). [22] |
| Vedolizumab | Prospective registry included 99 exposed, 76 disease-matched biologic-exposed, and 100 unexposed pregnancies; follow-up extended to 1 year postpartum. [174] |
| Pediatric ulcerative colitis | Acute severe colitis requires tight monitoring and timely medical and surgical intervention. [98] |
| Environmental exposure | Passive-smoking review assessed IBD incidence and outcomes; prenatal acid-suppressive exposure study assessed subsequent childhood IBD risk. [99][145] |
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