Preoperative Imaging Features of De Garengeot's Hernia Containing Low-Grade Appendiceal Mucinous Neoplasm: A Case Report.

De Garengeot's hernia is a femoral hernia involving the appendix. An appendiceal mucinous neoplasm within this hernia is exceptionally rare. We report a case of a 68-year-old woman presenting with a right inguinal mass. Ultrasonography identified the appendix within the femoral hernia sac, appearing as a tubular hypoechoic structure with inflammatory changes and a blind end tracing to the cecum. Contrast-enhanced Computed tomography (CT) revealed a well-defined cystic mass in the right femoral hernia with enhancing walls and septa and non-enhancing internal content, findings suggestive of an appendiceal mucinous neoplasm. Intraoperatively, a femoral hernia containing the appendix (De Garengeot's hernia) was identified. Postoperative pathology confirmed a distal low-grade appendiceal mucinous neoplasm within the appendix. This case highlights the complementary value of ultrasonography and CT in preoperative diagnosis and aims to improve recognition of femoral hernias by demonstrating key diagnostic features on retrospective image analysis-including localization of the hernia sac inferior to the inguinal ligament on CT and identification of the appendiceal lumen abruptly closing at the femoral ring on ultrasound-thereby enabling informative imaging reports to guide optimal clinical management.