Retroperitoneal Ectopic Pregnancy Involving the Renal-Adrenal Region.

Abdominal ectopic pregnancy is a rare and potentially life-threatening form of extrauterine gestation. Retroperitoneal implantation is exceptionally uncommon, and involvement of the renal-adrenal region has been only rarely described. We report the case of a 43-year-old woman who presented with acute abdominal pain, abnormal uterine bleeding, and a positive pregnancy test. Initial imaging demonstrated abundant intraperitoneal fluid without evidence of an intrauterine or adnexal gestation. Following the onset of hemodynamic instability, emergency exploratory laparotomy was performed, precluding further preoperative imaging evaluation. Intraoperative findings revealed hemoperitoneum and a hemorrhagic retroperitoneal lesion involving the left renal-adrenal region, requiring radical nephrectomy and adrenalectomy for definitive hemorrhage control. Histopathological evaluation demonstrated decidualized tissue with extensive hemorrhagic necrosis adjacent to adrenal tissue. Although chorionic villi were not identified, likely because of extensive hemorrhagic necrosis and tissue degeneration, the combination of the markedly elevated preoperative serum β-human chorionic gonadotropin (β-hCG) concentration, absence of an intrauterine or adnexal pregnancy, intraoperative findings, histopathological evidence of decidualized tissue, and sustained postoperative decline in serum β-hCG concentrations provided strong clinicopathological support for the diagnosis of retroperitoneal ectopic pregnancy. This case highlights the diagnostic challenges posed by atypical retroperitoneal implantation and underscores the importance of integrating clinical, surgical, biochemical, and histopathological findings when conventional histopathological confirmation is limited.