Fetus in Fetu: Lessons Learned from a Large Multicenter Cohort Study

Area of Science:

• Pediatric Surgery
• Developmental Biology
• Congenital Anomalies

Background:

• Fetus in fetu (FIF) is an exceptionally rare developmental anomaly resulting from abnormal twinning.
• Most existing literature comprises isolated case reports, limiting comprehensive understanding.

Purpose of the Study:

• To consolidate and analyze unpublished cases of FIF from multiple tertiary centers.
• To establish evidence-based criteria for the diagnosis, workup, and management of FIF, including intraoperative risk assessment.

Main Methods:

• A retrospective survey was distributed to a national pediatric surgery group to collect unpublished FIF cases over 20 years.
• The collected cohort was analyzed for clinical presentation, diagnostic approaches, surgical management, and patient outcomes.

Main Results:

• Ten FIF cases were identified between 1998 and 2018, with a mean presentation age of 4 months.
• Computed tomography and ultrasound were primary diagnostic tools. Surgical resection was curative in nine cases.
• Two cases with FIF near the biliary tree experienced severe intraoperative or fatal postoperative complications.

Conclusions:

• Complete surgical excision is the definitive treatment for FIF, typically leading to excellent long-term outcomes.
• Mortality is infrequent but associated with biliary tract involvement and right upper quadrant retroperitoneal locations.
• Increased surgical risk may correlate with FIF proximity to the biliary tree and the presence of immature pathological elements.