An omental abscess mimicking an intra-abdominal tumor.

Here, we report the case of a 12-year-old boy who presented with intermittent lower abdominal pain; subsequently, an intra-abdominal mass found by abdominal ultrasound. Initially, an intra-abdominal tumor was suspected according to the results of the physical examinations, laboratory data, and imaging studies. A surgical excision was performed, and pathological examination revealed an omental abscess without evidence of intestinal perforation or a residual foreign body. The patient's history consisted solely of receiving an open appendectomy for a ruptured appendicitis 2 years prior. This is an extremely rare case of a post-appendectomy omental abscess forming after such a long interval, but no evidence of residual appendiceal tissue or foreign bodies could be identified.