Background
The appendix is a blind ending hollow GI organ that is found in the cecum, just distal to the fatty ileocecal valve. With very limited confirmed function, the appendix is theorized to have certain roles: may serve as a site for symbiotic gut flora, may be involved in endocrine fetal development or may contribute to immune health. However limited its function may be, it is a well-documented site for pathology. Other than the commonly encountered appendicitis, the appendix may serve as a site for primary neoplasms, may be involved in IBD and can be a site for lesion implantation. The purpose of this exhibit is to review uncommon appendiceal pathology and their imaging characteristics.
Educational Goals / Teaching Points
Learn how to identify the appendix on imaging. Understand the different imaging characteristics for malignant processes, IBD and implanted pathology of the appendix. Learn of the secondary issues that can arise with appendiceal lesions.
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
When evaluating the appendix, it is important to look for “clues” to aid the differential. For classic appendicitis, one would look for a diameter>7mm, wall thickness >2mm , periappendiceal fat stranding and an appendicolith; age of the patient may also help. When evaluating other appendiceal pathologies, similar tactics can better lead to a diagnosis. Appendiceal cancers can be classified into the more common neuroendocrine tumor (NET) category or as carcinomas (usually mucinous adenocarcinoma). NET’s usually present as small masses near the appendix tip and can be complicated by obstruction or mucocele formation. Carcinomas, specifically mucinous subtype can be distinguished as a cystic mass in a dilated appendix (low density on CT or intense on T2 weighted sequences); these can be accompanied by mural calcification, further solidifying the diagnosis. It is important to note that mucinous carcinoma rupture has consequences and can result in pseudomyxoma peritonei (implantation of mucinous content in the peritoneum) spreading cancer and can serve as sites of adhesions. For IBD related appendicitis, patient history is important and noting surrounding bowel inflammation: for example, associated ileitis in Crohn’s or pan colitis in a patient with Ulcerative Colitis (termed ulcerative appendicitis). Implantation can also occur with the appendix; examples being metastatic lesions or gynecologic etiologies, such as endometriosis. For appendiceal implanted pathology, history is key as well as interval growth/stability. In patients with known endometriosis, recurring pain (perimenstrual) associated with a history of infertility can raise the suspicion of endometrial implants as well as lesion stability. These patients can also present with appendiceal intussusception as a complication.
Conclusion
Learning the patient’s history, assessing nearby organ pathology and delineating appendiceal lesions can greatly assist in narrowing down a differential. There are many types of appendiceal pathologies and accurate lesion characterization is pivotal for patient care and further management.
