Background: Crohn's disease (CD) is a chronic and progressive disease causing bowel damage (BD) which will lead to complications and surgery. Recently, the Lemann Index (LI) has been developed to measure the cumulative structural BD at a given time independent of disease activity. In this retrospective study, we investigated factors potentially related to structural BD progression in CD as expressed by changes in LI score over time.
Methods: We studied a cohort of 63 patients with 2 serial abdominal cross-sectional imaging studies (CT and/or MRI) at least 24 months apart, over a period of 5 years of follow-up at a tertiary IBD centre. Imaging and endoscopic data were used to compute LI using a Microsoft Access-based calculator. Changes in LI between the 2 time-points were calculated (delta LI, DLI = LI2-LI1) and patients were classified into 2 groups: those with zero or negative DLI values (stable or improved, iDLI) and those with positive DLI values (deteriorated, dDLI). The percentages of interval time (IT) with symptomatic disease luminal and/or perianal, increased CRP and exposure to various treatments were estimated. Non-parametric statistical analyses for independent and paired groups were performed to identify factors related to BD progression.
Results: In the entire CD cohort, median LI2 score increased significantly (median LI2, 8.5 versus median LI1, 7.5; p=0.021) over a median period of 30 months. LI increased (dDLI) in 32 patients (51%) and remained stable or decreased (iDLI) in 31 patients (49%). There were no significant differences in baseline characteristics between the 2 groups except for more common prior exposure to 2 biologics and more frequent active disease in dDLI group (Table 1). Factors independently associated with a significant increase in median LI2 were: persistent symptomatic disease during >50% IT (DLI=1.62, z=2.685, p=0.007), persistent CRP elevation >50% IT (DLI=1.31, z=2.103, p=0.035), frequent or continuous steroid use (DLI=2.2, z=3.309, p=0.001) and significant changes in treatment (DLI=2.2, z=2.418, p=0.016) during the interval period (Wilcoxon signed-rank test, Figure 1).
Conclusions: Our results show that ongoing Crohn's disease activity as indicated by persistent symptomatic disease, persistent CRP elevation, frequent steroid use and changes in treatment is associated with progressive bowel damage.