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.

中文翻译：

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胎儿早期脾脏及其周围器官的三维形态学分析

脾脏的形态存在差异，被认为在妊娠第三个月获得确定的形状。然而，很少有研究调查胎儿生命前 3 个月的脾脏发育。本研究旨在确定妊娠第三个月期间脾脏的三维 (3D) 形态发生。在这项研究中，对 30 个胎儿标本（头臀长 [CRL]：22-103 毫米）进行了磁共振成像分析。我们手动分割了脾脏、胃和肾上腺，重建了 3D 模型，并分析了这些器官的体积和形状。结果表明，与其他器官相比，脾脏大小的变化较大。脾脏形态根据脾表面的数量分为二面型、三面型、四面型、五面型、卵圆形和不规则形六种类型。两面脾仅在小样本中观察到，而三面和四面脾在较大样本中观察到。我们还发现，随着 CRL 的增大，胎儿脾表面的数量也随之增加。此外，3D 模型表明，一些标本在不与邻近器官接触的情况下形成了脾表面。这表明脾表面可能不仅是由来自所面对的器官的压力引起的，而且是由内在程序引起的。这项研究可以更好地了解胎儿早期脾脏的正常发育，并可能有助于未来研究脾脏先天性形态异常的研究。