Polysplenia syndrome is a malformation with impaired visceral lateralization; it consists in the incomplete development of the spleen which is replaced by two or more splenules (1-3 cm phi). This malformation is often associated with other anomalies and is more frequently seen in situs inversus and situs ambiguus. On the basis of their findings in 3 cases, the authors describe the main US and radiographic patterns of polysplenia syndrome, that is: polysplenia syndrome associated with situs solitus (several splenules where the spleen should be, without other anomalies); polysplenia syndrome associated with situs ambiguus (splenules in the right hypochondrium with such anomalies as "umbrella-like" liver and the absence of the hepatic segment of the inferior vena cava and enlargement of both azygos and hemiazygos veins); polysplenia syndrome associated with situs viscerum inversus (right-sided splenules, with transposition of abdominal and thoracic organs). The splenules exhibit the same echogenicity as the liver; when situs viscerum ambiguus is present. US patterns of splenuli are equivocal and may mimic liver metastases. On the contrary, CT allows better demonstration of both the anomaly and the associated malformations.
