Intestinal ultrasound detects an increased diameter and submucosal layer thickness in the appendix of patients with ulcerative colitis compared to healthy controls – a prospective cohort study

Background: Increasing evidence suggests that appendicectomy as alternative treatment for ulcerative colitis (UC), especially in patients with histopathological appendiceal inflammation. Intestinal ultrasound (IUS) is a non-invasive diagnostic modality to characterise appendiceal inflammation. Aims: To assess appendiceal IUS characteristics in UC patients and compare findings to healthy controls (HC). Methods: In this prospective study, appendiceal IUS was performed in consecutive UC patients with active (A; n = 35) or quiescent (Q; n = 30) disease and in HC (n = 30). Transverse appendiceal diameter (TAD) and additional IUS parameters (bowel wall thickness, submucosal layer thickness and colour Doppler signal) were assessed. Results: The appendix was visualised in 41/65 UC patients (63.1%; A vs. Q: 23/35 vs. 18/30, p = 0.67) and 18/30 (60%) HC. UC patients had a higher TAD (A: 5.5 mm, Q: 5.0 mm, HC: 4.3 mm; A-HC p < 0.01; Q-HC p = 0.01, A-Q p = ns) and submucosal layer thickness (A: 1.0 mm, Q: 1.0 mm, HC: 0.7 mm; A-HC p < 0.01, Q-HC: p = 0.01, A-Q: p = ns) when compared to HC. A TAD ≥6 mm corresponding to an ultrasonographic suspicion of acute appendicitis was mainly reported in A-UC patients (A: 43%; Q: 6%; HC: 0%, p = 0.01) and occurred irrespective of disease extent. However, none of the patients had a clinical suspicion of acute appendicitis. Conclusion: A TAD ≥6 mm was predominantly seen in A-UC. TAD was higher in UC patients compared to HC irrespective of disease activity and was characterised by an increased submucosal layer thickness. IUS therefore has the potential to identify UC patients with appendiceal inflammation.