Introduction and importance: Fetus-in-fetu (FIF) is a rare congenital anomaly of embryogenesis in which a malformed twin is enclosed within the body of its host. FIF represents an uncommon cause of abdominal mass and is classically distinguished from teratoma by the presence of a vertebral column, limb buds, or other organized organ systems. While most reported cases occur in the retroperitoneal region, FIF has also been documented in atypical sites, including the cranial cavity and scrotal sac. Case presentation: We present a case of a 3-month-old boy who exhibited irritability and progressive abdominal distention since birth. A computed tomography scan revealed a large, well-defined heterogeneous lesion in the left upper quadrant of the abdomen. Laparotomy was done. An encapsulated retroperitoneal mass was identified on the left side of the abdomen. Careful dissection allowed for the complete excision of the mass. Histopathological analysis confirmed the diagnosis of FIF. The postoperative period was uneventful, and follow-up at 6 months demonstrated a good clinical outcome. Clinical discussion: Congenital masses, such as FIF, are often underdiagnosed or inadequately managed in low-resource settings due to limited diagnostic and surgical infrastructure. Strengthening imaging capabilities and surgical planning is essential to improve outcomes. Conclusion: This case underscores the challenges of diagnosing and managing FIF in resource-limited settings. Raising awareness among healthcare providers at primary and secondary facilities, together with early recognition and timely referral, is essential not only for improving patient outcomes but also for establishing the true incidence and prevalence of this rare condition in Afghanistan and similar developing countries.
Rahimi et al. (Mon,) studied this question.