Appendiceal endometriosis mimicking acute appendicitis in a young woman: A case report.

Appendiceal endometriosis is a rare form of extragenital endometriosis that can mimic acute appendicitis. This reports presents the case of a 19-year-old woman with no significant medical history who presented with right-sided abdominal pain, nausea, and lightheadedness. Physical examination revealed right lower quadrant tenderness and a positive Rovsing sign. Laboratory studies showed no leukocytosis, and her modified Alvarado score was 4. Computed tomography of the abdomen and pelvis demonstrated mild fluid and inflammatory changes near the base of the cecum extending toward the right adnexa, raising concern for acute appendicitis versus a ruptured ovarian cyst. Pelvic ultrasound identified a complex cystic structure in the right ovary with adjacent free fluid, while appendicitis could not be excluded. Due to persistent symptoms and diagnostic uncertainty, laparoscopic appendectomy was performed. Intraoperative findings included hemoperitoneum, endometriotic lesions, and possible rupture of a right ovarian follicle. Histopathological examination revealed appendiceal serosal endometriosis. This case underscores the diagnostic challenge of appendiceal endometriosis and the importance of considering gynecologic etiologies in young women presenting with right lower quadrant pain.