Sonographic diagnosis of a retroperitoneal dermoid cyst in a young girl

We describe the detection and management of a retroperitoneal dermoid cyst in a young girl. Transabdominal ultrasound revealed in the pelvis a complex mass with anechogenic and echogenic components characteristic of a dermoid cyst. Initially, it was presumed to be of ovarian origin, because extragonadal dermoid cysts are very rare in adolescence; however, the findings on physical examination were normal. Laparoscopy was performed but failed to identify a cyst. Ultrasound examination was repeated intraoperatively and confirmed the presence of the cyst, which was then removed by laparotomy from the retroperitoneum. This case illustrates the significance of ultrasonography in the diagnosis of a rare condition in adolescent gynecology and demonstrates the possibility of performing ultrasound scanning intraoperatively to confirm the presence of a mass which was not identified by laparoscopy.