Bowel Damage in Crohn's Disease: Direct Comparison of Ultrasonography-based and Magnetic Resonance- based Lemann Index

Background: The Lemann index (LI), calculated by magnetic resonance (MR) or computed tomography enterography in association with endoscopy, was developed to assess bowel damage (BD) in Crohn's disease (CD). Our aim was to investigate the concordance between ultrasonography-based Lemann index (US-LI) and magnetic resonance-based Lemann index (MR-LI). Methods: We prospectively evaluated all consecutive patients with CD referred to our IBD Unit. All patients had undergone endoscopy, US and MR within 1 month. US-LI and MR-LI were calculated by scoring previous surgery, location, extension, and intestinal complications. Furthermore, we evaluated the association between LI and: CD duration, Harvey-Bradshaw index, and other relevant clinical features. In accordance with recent literature, an LI >4.8 was considered indicative of BD. Results: Seventy-one patients with CD were examined. About CD location, 36% showed ileal disease (L1), 10% showed colonic CD (L2), whereas 54% had an ileocolonic disease (L3). Moreover, 27% of patients presented a noncomplicated behavior (B1), 45% had almost one stricture (B2), whereas 28% showed penetrating CD (B3). Perianal CD was observed in 16% of subjects, whereas 40% had undergone previous surgery. MR-LI and US-LI were 6.62 (95% confidence interval, 4.2-9.7) and 6.04 (95% confidence interval, 3.6-9.2), respectively (r = 0.90; P < 0.001), with 35 patients (49%) showing an LI indicative of BD. No significant correlation was evident between LI and Harvey-Bradshaw index (P = 0.9), whereas a significant correlation was found between both US-LI/MR-LI and CD duration (P= 0.01). Conclusions: US-LI shows high concordance with MR-LI and could be considered a good option for assessing BD in CD by using a highly available and relatively inexpensive procedure.