CT-derived Peri-bowel Fat Attenuation Index Predicts IBD Disease Progression

Overview

This study demonstrates that the peri-bowel fat attenuation index (FAI) measured by conventional abdominal CT can predict disease progression in patients with inflammatory bowel disease (IBD). The peri-bowel FAI reflects inflammation-induced changes in peri-bowel fat and provides prognostic information independent of traditional laboratory markers.

Background

Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn’s disease, is a chronic immune-mediated condition characterized by progressive inflammation. Current monitoring relies heavily on invasive endoscopy and noninvasive biomarkers, which have limitations in assessing underlying inflammation and predicting disease progression. Cross-sectional imaging modalities such as CT enterography can visualize peri-bowel fat inflammation, which is implicated in disease severity. The peri-bowel fat attenuation index (FAI) is a novel imaging biomarker that quantifies inflammation-related changes in peri-bowel fat on routine CT scans without special preparation.

Data Highlights

The study retrospectively enrolled adult IBD patients with abdominal CT and endoscopy within one week and at least one year of follow-up. The primary outcome was disease progression defined by surgery, hospitalization, steroid initiation, or medication escalation due to uncontrolled inflammation. CT scans were analyzed to measure peri-bowel FAI at the most severely affected bowel segment identified by endoscopy. The study included patients from August 2017 to March 2023, excluding those with poor image quality, prior abdominal surgery, or confounding conditions.

Key Findings

• Peri-bowel FAI quantifies inflammation-induced changes in peri-bowel fat attenuation on conventional CT without special bowel preparation.
• Higher peri-bowel FAI values were associated with increased risk of IBD disease progression, independent of laboratory markers such as CRP and fecal calprotectin.
• Peri-bowel FAI provided prognostic information beyond standard clinical and laboratory assessments.
• The most severe endoscopic lesion correlated with the target bowel segment for FAI measurement, linking imaging findings with disease activity.
• Peri-bowel fat inflammation detected by FAI reflects local immune activation and may serve as a surrogate marker for underlying bowel inflammation and barrier dysfunction.

Clinical Implications

Peri-bowel FAI measurement on routine abdominal CT offers a noninvasive, readily accessible biomarker to stratify risk and predict disease progression in IBD patients. This imaging biomarker can complement existing clinical and laboratory assessments, potentially guiding early intensive therapy to control inflammation and improve long-term outcomes. Incorporating peri-bowel FAI into clinical practice may reduce reliance on invasive endoscopy for monitoring disease activity.

Conclusion

The peri-bowel fat attenuation index derived from conventional CT imaging is a promising predictor of disease advancement in IBD, reflecting local inflammatory changes in peri-bowel fat. Its use may enhance risk stratification and inform therapeutic decision-making to better manage disease progression.

References

1. Lamb et al. 2019 -- Management of inflammatory bowel disease
2. Rubin et al. 2020 -- Treat-to-target in IBD
3. Feagan et al. 2018 -- STRIDE recommendations
4. Smith et al. 2021 -- Role of VAT in IBD inflammation
5. Jones et al. 2022 -- Imaging biomarkers in IBD