Background and aims: Bowel damage [BD] will develop in the majority of Crohn’s disease [CD] patients. Recently, the Lémann Index [LI] was developed to measure BD. Methods: This was a prospective single-center cohort study. All included patients underwent full evaluation for bowel damage before starting anti-TNF therapy and every year thereafter. BD at baseline and during follow-up was measured using the LI. We assessed the impact of anti-TNF therapy on BD. We also assessed the sensitivity to change of the LI and the relationship between BD progression and disease outcomes, including the need for surgery. Results: Thirty CD patients were enrolled [13 on infliximab, 17 on adalimumab]. Median baseline LI was 9.1 [range, 1.6–34.1]. Median follow up was 32.5 months [range, 10–64]. By a ROC curve analysis, a LI >4.8 defined CD subjects with BD. Any change >0.3 in the LI was related to BD change [AUC 0.98]. During follow-up, 83% of subjects had BD regression and 17% had BD progression. Anti-TNF therapy significantly reduced LI at 12 months [p=0.007]. Subjects with BD progression were more likely to undergo major abdominal surgery through the follow-up period [HR 0.19, p=0.005]. Conclusion: The LI has good sensitivity to change. Anti-TNFs agents are able to reverse BD in some CD patients. BD progression as measured by the LI may be predictive of major abdominal surgery in these patients.