Endometriosis of the appendix with decidual polyp formation: a rare cause of acute appendicitis during pregnancy.

We report a case of a 28-year-old female, Grava 2, Para I, Ab. 0, who presented acute abdominal pain on the 21st week of her gestation. A diagnosis of acute appendicitis was entertained and an appendectomy performed. The pathologic specimen revealed an inflamed appendix with endometriosis and a marked decidual reaction. A decidual polyp, which occluded most of the appendiceal lumen, is proposed as a rare cause of acute appendicitis during pregnancy.