Preoperative diagnosis of a “humanoid” fetus in fetu using multimode ultrasound: a case report

BACKGROUND: Fetus in fetu (FIF) is a rare congenital anomaly. The preoperative diagnosis of FIF and differentiating it from teratoma and other abdominal tumors can be challenging for radiologists. Clarification of the blood supply and the relationship with the surrounding vessels is especially helpful for successful surgery; however, multimode ultrasound (US) performed for FIF has rarely been explored. Here, we first report a “humanoid” FIF case diagnosed by multimode US examinations, with the use of contrast-enhanced ultrasound (CEUS) for clarifying the blood supply features. CASE PRESENTATION: A 25-day-old preterm male infant was referred to our hospital for surgery. The US and computed tomography (CT) examinations led to a diagnosis of teratoma at the local hospital. The laboratory workup at our hospital revealed an elevation of total bilirubin, direct bilirubin, indirect bilirubin, alpha-fetoprotein, and neuron-specific enolase levels. A precise diagnosis and differentiation from teratoma, hepatoblastoma, neuroblastoma and other abdominal tumors were needed. In addition, the blood supply and the relationship with the surrounding vessels needed clarification prior to surgery. Multimode US examinations were performed and the features of a “humanoid” FIF as well as the blood supply for the abdominal lesion of the infant were suggested by grayscale US, color Doppler flow imaging (CDFI), and CEUS. Furthermore, CDFI and CEUS revealed an aorta-like structure and umbilical cord-like blood vessels in the “humanoid” FIF, and the CEUS helped with marking the surface of the infant’s abdominal wall. To the best of our knowledge, this is the first case report of CEUS in FIF, and the blood supply was clearly demonstrated in the FIF. The intraoperative findings confirmed our multimode US findings and revealed a “humanoid” FIF. The infant quickly recovered after the operation and had no positive findings at the 2-year follow-up visit. CONCLUSIONS: Multimode US was helpful in diagnosing the rare FIF without radiation exposure. Specifically, CEUS clearly demonstrated the limb branch vessel-like structures, the abdominal aorta-like structure and the blood supply, which was useful for the FIF diagnosis and for avoiding damage to important vessels during the operation.