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

As the authors of the study that explored intestinal ultrasound (IUS) assessment of the appendix in ulcerative colitis patients and healthy controls, we read the editorial of Drs. Suarez and Novak with great interest.1 The therapeutic efficacy of appendicectomy in ulcerative colitis (UC) patients has been examined thoroughly via multiple prospective trials.2– 4 These studies concluded that patients with appendiceal inflammation tend to respond to therapeutic appendicectomy.4,5 It is thus of great importance to identify preoperatively UC patients with appendiceal inflammation to encourage patienttailored policy in an ever growing treatment armamentarium. More than half of UC patients demonstrate appendiceal inflammation, regardless of disease activity. Approximately one in five patients with UC demonstrates endoscopic periappendiceal red patch (PARP) on colonoscopy, suggesting appendiceal inflammation.6 A diagnostic modality other than endoscopy should therefore contribute to the detection of appendiceal inflammation that are not detectable via endoscopy. As IUS has been introduced as a disease monitoring modality in UC and is routinely being used for the diagnosis of acute appendicitis, we aimed to involve IUS in the detection of appendiceal inflammation. We found marginal differences in diameter of the appendix and bowel wall thickness between UC patients and healthy controls, implying a potential role for routine IUS of the appendix in UC patients.7 Drs. Suarez and Dr Novak mention absence of assessment of interobserver agreement as a limitation of our study. As this was an explorative study, the next step indeed is assessment of interobserver agreement. Although a recent study concluded strong interobserver agreement for IUS in UC, the visibility rates of 60%– 66% in the current study probably affect interobserver agreement to a certain extent.8 Next to agreement, correlation to a gold standard is mandatory. The presence of appendiceal inflammation is assumed if the transverse appendiceal diameter (TAD) exceeds 6 mm, according to the cutoff for acute appendicitis on ultrasound.9 Therefore, we are currently conducting an extension of the current study, in which UC patients underwent colonoscopy, appendiceal IUS and consecutive appendicectomy. The correlation between endoscopic PARP, appendiceal IUS findings and histopathologic appendiceal inflammation will be explored. Interobserver agreement will also be assessed. The results of the extension study will give us deeper insights into the pathophysiology of appendiceal inflammation in UC and potentially offer cutoff values for appendiceal ultrasound to diagnose appendiceal inflammation noninvasively. The authors' declarations of personal and financial interests are unchanged from those in the original article.7