Three-dimensional morphological analysis of the human spleen and its surrounding organs during the early fetal period.

The spleen has variations in its morphology and is considered to acquire a defined shape in the third month of gestation. However, few studies have investigated spleen development during the first 3 months of fetal life. This study aimed to determine the three-dimensional (3D) morphogenesis of the spleen during the third month of gestation. In this study, 30 fetal specimens (crown-rump length [CRL]: 22-103 mm) were subjected to magnetic resonance imaging analysis. We manually segmented the spleen, stomach, and adrenal gland, reconstructed 3D models, and analyzed the volume and shape of these organs. The results showed that the variation in spleen size was large compared to that in other organs. Spleen morphology was classified into six types based on the number of splenic surfaces as follows: two-faced, three-faced, four-faced, five-faced, ovoid, and irregular. Two-faced spleens were only observed in small specimens, whereas three- and four-faced spleens were observed in larger specimens. We also revealed that the number of fetal splenic surfaces increased as CRL enlarged. Additionally, 3D models indicated that some specimens formed their splenic surfaces without contact with the adjacent organs. This suggested that the splenic surface may be caused not only by pressure from the faced organs but also by an intrinsic program. This study may provide a better understanding of the normal development of the spleen during the early fetal period, and may potentially assist future studies in investigating congenital morphological anomalies of the spleen.