Editorial: routine use of intestinal ultrasound in ulcerative colitis—are we missing the appendix?

Although often perceived as a vestigial or redundant organ, the appendix is increasingly recognised as important in the pathogenesis of ulcerative colitis (UC); for example, there is evidence demonstrating risk reduction in the development of UC after appendectomy (OR 0.37, 95% CI 0.29– 0.46).4 Similar rates of appendiceal inflammation have been reported in specimens from patients with active and quiescent UC and with no influence of baseline disease extent.5 Appendectomy has been proposed as an alternative therapeutic surgical approach before considering colectomy in patients with refractory UC, with improvement in quality of life and avoidance of colectomy in over 70% at 3year followup.6– 8 Further data from ongoing multicentre clinical trials are needed to confirm and further establish appendectomy as part of the standard of care in medically refractory populations.9 Reijntjes and collaborators explored IUS assessment of the appendix in ambulatory patients with UC in a singlecentre prospective cohort study, including a range of UC disease activity.10 There were 35 patients with active UC, 30 with quiescent UC, and 30 healthy controls (HC); visualisation of the appendix was reported in 63.1% of the UC patients and 60% of the HCs. Interestingly, the transverse appendiceal diameter (TAD) was significantly higher in the patients with UC than HCs regardless of the disease activity (5.5, 5.0, and 4.3 mm, respectively). Also, a TAD >6 mm (usually compatible with acute appendicitis) was reported with statistical significance in active (43%) versus quiescent UC (6%) and HCs (0%), p = 0.01. This study raises important considerations and potential implications for modifying UC outcomes. First, the almost perfect agreement between IUS and disease activity parameters (k = 0.91) supports using IUS in UC as part of the noninvasive, patientcentred armamentarium for disease activity assessment. Second, it suggests that intentional IUS assessment of the appendix in all patients with UC may be informative, particularly in active cases. Perhaps it should be routinely recommended. It is essential to recognise that visualising the appendix can be challenging, and more technical expertise may be needed. Even in expert hands, as in this study, the success rate for appendix visualisation was approximately 60% overall. There were limitations in the study. For example, there was no direct assessment of the interobserver agreement and, since there was infrequent endoscopic assessment temporally related to IUS, a lack of histological correlation with the sonographic findings. However, the presented data were provocative, as they highlighted an opportunity to take advantage of this noninvasive and practical assessment tool to guide tailored therapeutic strategies for patients with refractory UC. True modification of outcomes is the ultimate goal in UC. Regular interval transmural assessment through IUS may provide insights into disease activity, response to therapy, and also the underlying pathophysiology.