Sirenomelia is a very rare congenital developmental disorder of the lower extremities, and all the other derivatives from the caudal mesoderm, mainly the viscera i.e. kidneys, gonads and hindgut. In the majority of cases, it is incompatible with life in the neonatal period as it is associated with renal agenesis. The importance of detecting this anomaly in the first trimester lies in this lethality in order to offer the option of termination of pregnancy at an earlier gestation. Appropriate counselling at diagnosis is essential to give the couple a clear picture of what they might expect postnatally regarding the renal anomalies or the many surgeries which might be required for the lower limbs and viscera. We present a case series (n = 5) diagnosed by ultrasound at our center between January 2014-2020. Through this brief article, we aim to give a key to the antenatal diagnosis of this rare anomaly, an aid on how not to miss it and its subsequent management.

Current technology and rapidly evolving Three-dimensional (3D) and Four-dimensional (4D) ultrasound techniques with advanced High Definition live (HD live) application has made Fetal medicine accomplishable. The introduction of high-frequency probes and evolution from hand swept slice acquisition to mechanically oscillating to electronically oscillating transducers with complex post-processing algorithms has led to the visualization of 3D view or real-time 3D view (4D) of fetal structures. In this review, we present a rare antenatal case of duplication of the gall bladder, highlight the utility of 3D/4D imaging and HD live Silhouette aiding in better understanding anatomical relationships, diagnosis, and implication in counseling.