Reply to Dr. Meyers et al regarding 'Beyond acute appendicitis: imaging of additional pathologies of the pediatric appendix'.

Sir, We would like to thank Dr. Meyers et al. [1] for their comments and question regarding our recently published article discussing alternative pathologies of the appendix beyond primary acute appendicitis [2]. When evaluating the appendix, we believe two main clinically relevant decision points must be addressed. The first is to determine whether or not the appendix is normal. If it is abnormal, the radiologist should look for any findings that would preclude urgent surgical intervention. The most frequent and straightforward such finding is that of appendiceal perforation with an associated abscess, whereby an abscess drainage procedure performed by interventional radiology staff may supplant urgent appendectomy as the primary intervention. However, as discussed in our article, there are other entities that can mimic acute bacterial appendicitis, such as cystic fibrosis and inflammatory bowel disease [2], where careful analysis of the clinical details and the imaged periappendiceal structures may provide clues that an urgent appendectomy is not warranted and that markedly different clinical management is required. Although viral appendicitis has been described, there are not sufficient data to show that it can be readily differentiated from early bacterial appendicitis by imaging [3, 4]. Therefore if the appendix appears inflamed by imaging, even if mild, and there are no clear clinical, laboratory or imaging clues to suggest that it may not be caused by acute bacterial appendicitis, an appendectomy is generally indicated, though this may be tempered by clinical examination from experienced surgical staff. Therefore the possibility of viral appendicitis does not affect the imaging algorithm at our institution (i.e. we do not think the radiologist has a role in suggesting this entity for which non-surgical management has been proposed [3]). In our standardized, structured reports for US exam of the appendix [5], we list an indeterminate category among our impression choices. This option may be employed when findings are not clear (e.g., the appendix is mildly dilated without compression but compresses normally with only mild tenderness and surrounding fluid but without adjacent fat induration) and may trigger a surgical consult, overnight monitoring or further imaging depending on the clinical scenario. This being said, we have certainly encountered cases where imaging and operative exploration both suggested mild appendiceal inflammation yet, after resection, the appendix was interpreted to be normal by the examining pathologist. Given that our pathologists are not routinely making assessments of the appendix detailed toward the exclusion of viral appendicitis, it is possible that these seemingly discordant cases could be caused by viral appendicitis. Whether a viral appendicitis can cause a clinical syndrome below the threshold of routine radiologic and histological interrogations is a different matter and cannot be addressed based on the current literature. K. R. Dietz Department of Radiology, University of Minnesota Amplatz Children’s Hospital, Minneapolis, MN, USA