总结内寄生胎产前超声影像学特征。

对2009年1月至2019年1月湖北省妇幼保健院产前超声检出胎体肿块，并经出生后手术及引产后病理检查证实的8例内寄生胎影像诊断资料进行回顾性分析。

产前超声声像图显示：8例胎儿胎体肿块均为囊实性，位于腹膜后4例，位于骶尾部2例，位于面部2例；最早发现胎体肿块为孕18^＋2周；其中2例发现胎体肿块为临产前。肿块最小径1.1 cm×1.1 cm，最大径16.0 cm×10.0 cm；与周围组织分界清，肿块增大致周围脏器不同程度受压移位。超声诊断：8例胎儿胎体肿块中4例最早于孕22^＋2周精准诊断为内寄生胎；2例胎体肿块产前诊断为畸胎瘤；2例骶尾部肿块产前鉴别不清是畸胎瘤或内寄生胎。临床结局：4例腹膜后胎体肿块在宿主胎儿出生后手术康复，随访至今未见复发；其余4例超声检查后引产。出生后检查：8例宿主胎儿共10个寄生胎，2例为双寄生胎；病理检查显示寄生胎内最多的组织是骨或软骨和肢芽（9/10）；其次为脊柱轴、皮肤和血管蒂（7/10），四肢长骨和毛发（6/10），肠管（5/10）。产前超声与产后病理诊断结果对照：产前超声正确诊断内寄生胎4例（4/8），寄生胎5个（5/10）。病理补充超声影像显示6个寄生胎有毛发、5个有肠管、1个有肾、合并畸形2个有脐膨出、2个为无脑畸形；1个寄生胎产前超声未检出闭合性脊髓脊膜膨出；1例产前超声认为是大寄生胎的骨性结构，出生后病理证实为双内寄生胎的小寄生胎，其脊柱轴为发育不全椎骨融合而成。

内寄生胎产前超声声像图有特征性表现，系统规范的产前超声对临床咨询和胎儿出生后选择手术治疗有重要意义。

To summarize the prenatal ultrasonic characteristics of fetus in fetu (FIF).

The ultrasound images of eight cases of pathologically-confirmed FIF were retrospectively analyzed at Maternal and Child Health Hospital of Hubei Province from January 2009 to January 2019.

Eight cases of FIF were enrolled in this retrospective study. Ultrasonic imaging showed heterogeneous cystic-solid masses with clear boundaries. The locations of masses included the retroperitoneum (4 cases), sacrococcygeal region (2 cases), and face (2 cases). In the 8 patients, 10 cystic-solid masses in fetus were found by ultrasound at different times of gestation from 18^{+ 2} to 38^{+ 1} weeks, with 2 cases having 2 parasites each. The size of masses ranged from the minimum of 1.1 cm×1.1 cm to the maximum of 16.0 cm×10.0 cm. The surrounding organs were compressed differently as a result of the mass effect. Four cases were diagnosed as FIF by prenatal ultrasound, 2 cases were thought to be teratomas, and 2 cases had an unclear diagnosis. The 4 cases with FIF in the retroperitoneum underwent surgery after birth and recovered with no recurrence, and the other 4 cases underwent induced labors. Pathologically, different organ components were found in 10 parasites, including bone/cartilage and limb buds (9/10), vertebral column, skin and vessels (7/10), long bones and hairs (6/10), and intestinal tracts (5/10). The coincidence rates between prenatal ultrasound and pathology were 8/9 cases of bone/cartilage, 6/7 cases of vertebral column, 5/6 cases of axial skeleton, and 5/7 cases of skin and vessels. Prenatal ultrasound failed to detect some organs, including hairs in 6 parasites, intestinal tracts in 5, kidney in 1, and combined malformations in 5 (umbilical bulge in 2 parasites, anencephalus in 2, and spina bififida in 1). One smaller parasite of twin FIF was misdiagnosed as the bony structure of a large parasitic fetus in prenatal ultrasound.

Ultrasonic manifestations of FIF are characteristic and systemic prenatal ultrasound has a very important role in the diagnosis of FIF.