Giant Serous Cystadenoma Masquerading as Ascites in an Adolescent by Ultrasound: A Case Report and Review of Diagnostic Challenges

Background Giant ovarian serous cystadenomas are uncommon in adolescents and present much like ascites, which may cause diagnostic delays and mistreatment. Correct imaging and laboratory workup are essential to allow treatment in time with the preservation of fertility. Case Presentation A 16-year-old girl was referred from the pediatric unit to the ultrasound unit of the teaching hospital in the southeast of Nigeria, with the symptoms of progressive abdominal distension, pain, a history of continuous vaginal bleeding and anemia. The initial ultrasound had indicated free peritoneal fluid. A large cystic mass almost filling the abdomen was seen on extended-field-of-view (EFOV) imaging. Laboratory results showed iron deficiency anemia and hormonal derangement. Surgical exploration revealed a 4.25 kg serous cystadenoma derived from the right ovary. A study of histopathology proved an origin from benign epithelium. Our case emphasizes that EFOV is valuable in distinguishing large cystic masses from ascites despite the predominantly bilobar mass and characteristic cut-off appearance, especially in environments with limited resources when used alongside laboratory workup and histology for management. Conclusion Giant serous cystadenomas, although rare in adolescence, should be kept in mind when adolescents present with unexplained abdominal enlargement. High level of attention to sonographic skill and vigilance in the clinic is crucial for resemble diagnosis and the best outcome.