Figure 9.

Acute appendicitis and a simple retention cyst. A,B: Imaging evaluation of a patient with acute pain in the right lower quadrant, showing an appendix (solid arrow) with an increased caliber (16 mm) and signs of peri-appendiceal inflammation (stars) that manifest as hyperechoic, non-compressible fat on ultrasound (A) and densification of the adjacent fat on an axial CT scan (B). A hypodense/cystic area (curved arrow) is observed at its distal end, suggesting a mucocele or a peri-appendiceal fluid collection. A retrospective review of a CT study performed one month before (not shown) revealed that a tiny cystic structure was already visible at the tip of the appendix. The appendectomy specimen showed a thickened appendix, and the histological diagnosis was acute appendicitis accompanied by peritonitis and epithelial hyperplasia, without neoplastic tissue (a simple retention cyst).