32 - Fetal Spleen

Abstract

The fetal spleen is an important center of hematopoiesis until the late fetal period. The fetal spleen is usually not seen on ultrasound (US) before 18 weeks. Normal values for fetal spleen dimensions have been proposed. From a clinical point of view, the rationale for developing normal values is the association of splenic size with hematologic and infectious diseases and developmental syndromes. Fetal splenomegaly is a classic sign of fetal anemia. A hypoplastic fetal spleen is much rarer and has been described in cases of DiGeorge syndrome and sickle cell anemia. Doppler measurements of the splenic artery are another potentially clinically useful aspect of US assessment of the fetal spleen. Several groups reported the association of splenic artery pulsatility and flow velocities with fetal growth restriction and anemia. Pathologic findings of the spleen discovered during prenatal US screening examinations are mostly related to the location or size of the organ and the occurrence of malformations. Accessory spleens are a common finding in adults and are typically located near the splenic hilus or the tail of the pancreas but can be found anywhere else in the abdomen, where they can be mistaken for tumors. Congenital splenic cysts are usually diagnosed during prenatal US from week 20 onward, typically as chance findings. The complete absence of the spleen (asplenia) and a condition with multiple small spleens (polysplenia) are rare anomalies and should raise the suspicion for associated laterality and cardiac defects.