Fetal splenic cyst: Change in size and shape with advancing menstrual age

A 32-year-old Japanese woman, gravida 2, para 1, was referred to our ultrasonography clinic because of an abnormal echo-free space located in the left upper quadrant of the fetal abdomen at 17 weeks, menstrual age. The course of her pregnancy had been uneventful. Ultrasound examination showed the echo-free space to be 1.1 cm x 1.3 cm, and was connected to the stomach (Figure 1). Values for biparietal diameter and femur diaphysis length were appropriate for a gestation of 17 weeks, menstrual age; no other abnormality was noted. At 19 weeks, the size of the space was unchanged, but separation from the stomach was clear (Figure 2). At 21 weeks, this echo-free space had decreased in size (0.5 cm X 0.7 cm), was even more clearly separated from stomach, and was considered to be located in the spleen (Figure 3). Ultrasound examination at 25 weeks, menstrual age, showed this echo-free space to be even smaller (0.3 cm x 0.5 cm), and location in the spleen was clear (Figure 4). A congenital splenic cyst was strongly suspected and serial ultrasound examinations thereafter revealed no changes in size or shape (Figure 5). The patient was delivered vaginally at 38 weeks of a viable female infant weighing 3,194 g. Ultrasound examination revealed a small cyst in the spleen of the child (0.5 cm x 0.8 cm) (Figure 61, and the final diagnosis was congenital splenic cyst.