OBJECTIVES: Appendiceal diverticulitis (AD) is frequently confused with acute appendicitis (AA)
however, AD carries a higher risk of perforation and malignancy than AA. We aimed to evaluate the preoperative diagnostic ability of transabdominal ultrasonography (US) for AD. METHODS: We included 74 patients who underwent appendectomy with a preoperative diagnosis of AA, AD, and US within a day of surgery. AD was diagnosed using US by identifying protruding, pouch-like hypoechoic structures beyond the appendiceal margin, whereas it was diagnosed using histopathology by identifying the invagination of the appendiceal epithelium into the muscularis propria. RESULTS: The median patient age was 45 years (61% males). Among the patients with a US diagnosis of AD, 9 patients had histopathological AD, while one patient did not. The other 64 patients without a US diagnosis of AD did not have histopathological AD. US showed 100% sensitivity, 98% specificity, 90% positive predictive value, 100% negative predictive value, and 99% accuracy for AD. A retrospective review of US images showed that 8 patients exhibited high echoic rims at the border of the hypoechoic structures among the 9 patients with histopathological AD. When this finding was incorporated into the US diagnosis of AD, the specificity increased to 100%. CONCLUSIONS: The diagnostic accuracy of US for AD is high. Not only are protruding pouch-like hypoechoic structures specific for the US diagnosis of AD, but also highly echoic rims at the border.