Introduction

Magnetic resonance enterography (MRE) has superior sensitivity over intestinal ultrasound (IUS) for established small bowel (SB) Crohn’s disease (CD), while retrospective studies suggest small intestinal contrast ultrasound (SICUS) may match computed tomography enteroclysis (CTE) accuracy. The incremental role of SICUS in periodic monitoring of established CD needs further exploration.

Aims & Methods

A prospective study was conducted at a high-volume tertiary gastroenterology center recruiting established CD patients (18-75 years) requiring SB evaluation. The accuracy of IUS followed by SICUS was assessed against CTE/MRE (within 24-48 hours) for detecting active SB disease, extent, bowel wall thickness (BWT), involved length, complications, and impact on management.

Results

A total of 407 patients (median age 36 years, 60.2% male) underwent IUS/SICUS followed by CTE (n=215) or MRE (n=192). SICUS demonstrated a sensitivity of 95.3% and specificity of 93.0% for detecting SB disease. For disease extent, sensitivity was 90.7% and specificity 90.5%. SICUS significantly improved stricture detection as compared to IUS (sensitivity 86.8% vs. 71.3%, p=0.0005). SICUS demonstrated high sensitivity of 91.7% for fistulas, and 87.5% for abscesses. SICUS correlated strongly with CTE/MRE for BWT (Spearman’s rho, R=0.667, p<0.001) and disease length (R=0.839, p<0.001). Missed lesions (n=17) and strictures (n=22) were predominantly in the proximal and mid-SB. Management changed in 9.3% (n=38) following CTE/MRE, primarily for surgical planning (n=8), therapy escalation (n=10), and stricture management (n=6) (table 1).

Conclusion

IUS and SICUS are highly accurate, non-invasive tools for monitoring SB CD, with SICUS improving stricture detection. While CTE/MRE remains essential for evaluating proximal and mid-SB disease and surgical planning, the limited incremental impact reinforces IUS/SICUS as effective first-line modalities (ClinicalTrials.gov: NCT 06125678).

References

Taylor SA, Mallett S, Bhatnagar G, et al; METRIC study investigators. Diagnostic accuracy of magnetic resonance enterography and small bowel ultrasound for the extent and activity of newly diagnosed and relapsed Crohn's disease (METRIC): a multicentre trial. Lancet Gastroenterol Hepatol. 2018 Aug;3(8):548-558. doi: 10.1016/S2468-1253(18)30161-4.

Introduction

Secondary loss of response to Infliximab(IFX) occurs in approximately half of patients with Inflammatory Bowel Disease(IBD), due to drug levels falling below the therapeutic range. This study evaluated IFX levels and related clinical and laboratory parameters and their impact on clinical outcomes.

Aims & Methods

Pre-infusion drug levels, associated laboratory data, and clinical parameters were evaluated in IBD patients receiving maintenance doses of IFX(5–15 mg/kg every 4–8 weeks) between Nov2021-Apr2025. Drug levels were measured using a bedside kit capable of quantitatively detecting values between 0.4–20µg/mL.

Results

A total of 1,059 single pre-infusion measurements from 455 patients and consecutive dual measurements at weeks 4 and 8 from 64 patients were evaluated. In the single and double measurement groups, 75.4% and 84.4% of patients had Crohn’s disease(CD), respectively. The most commonly used doses were 5 mg/8 weeks and 10 mg/4 weeks(Table 1) Drug levels were below 5 µg/mL in 33% of the measurements. Antibody positivity was present in 47.5% of 120 available measurements ranging from 0.4-20 µg/mL, showing no significant correlation with drug levels or immunomodulatory(IM) use (p=0.62 and p=0.61) However, for all positive antibody measurements drug levels were ≤ 3.5 µg/mL. CRP differed significantly across drug level groups, whereas albumin did not(Table 1). A weak negative correlation was found between IFX levels and CRP(r = -0.13, p = 0.001), with no correlation for albumin(p=0.54). In UC patients, the correlation between CRP and IFX levels was slightly stronger(r= -0.280, p=0.004).No significant associations were found between IM use and IFX levels >5 µg/mL(p=0.55), >10 µg/mL(p= 0.93), or >20µg/mL(p = 0.87). Abdominal pain was more common in patients with IFX levels <5 µg/mL (p=0.032) and <10 µg/mL (p=0.044). Smoking status was not associated with achieving IFX levels >5 µg/mL( p=0.57), >10 µg/mL (p=0.89), and >20 µg/mL (p=0.633). Among CD patients, those with IFX levels >5 µg/mL had significantly lower CDAI scores (p = 0.039), and lower daily stool frequency (p=0.002).Regression analysis showed that higher BMI (p=0.045), lower CRP(p < 0.001), higher IFX dose(p < 0.001), and CD diagnosis(p =0.014) to be independently associated with achieving IFX levels >5 µg/mL. These factors also predicted levels >10 µg/mL and >20 µg/mL, except for BMI at the >20 µg/mL threshold. In the dual measurement group, the median CRP levels at weeks 4 and 8 were 2.1(5.1) and 2.5(6.3), respectively (p = 0.108). Among patients with IFX >20 µg/mL at week 4, 75% maintained levels >5 µg/mL at week 8, whereas this rate was 64% for those with levels >10 µg/mL. Only 59.6% of those with >5 µg/mL at week 4 retained >5 µg/mL at week 8(all p <0.001). Week 4 IFX levels was 7.3 times higher than at week 8 for cases within measurable range.

Conclusion

One-third of patients demonstrated sub-therapeutic drug levels, which were associated with elevated CRP levels and worse clinical outcomes. Notably, the 5mg/4 weeks group exhibited higher drug concentrations compared to the 10mg/8 weeks group, suggesting that increased infusion frequency may contribute to achieving higher levels. Moreover, maintaining sufficient drug levels at week 8 requires substantially higher levels at week 4. Measurement of anti-TNF antibodies may not be fruitful if drug level is > 3.5µg/mL. These findings support the drug monitoring and personalized dosing to reduce the risk of loss of response and improve outcomes.