总结胎儿膀胱外翻（BE）产前超声（US）及磁共振成像（MRI）影像特征。

对2013年2月至2017年12月在湖北省妇幼保健院产前超声联合MRI诊断并经产后病理检查确诊为膀胱外翻4例（3例单胎为自然受孕，1例双胎为人工受孕）胎儿的超声影像表现进行总结。

4例胎儿产前超声显示共有的异常声像表现为：盆腔内膀胱未显示，脐带低置，耻骨联合分离，性别难以确定，羊水量正常；其中1例双胎之一合并右肾缺如伴脐带插入处下方膨出物，1例疑诊脊髓栓系。4例胎儿产前MRI显示与超声相同的异常影像表现，但4例耻骨联合分离均未显示，排除了超声疑诊脊髓栓系。与引产后X线及病理检查结果对照，产前MRI补充检出超声未显示的腹壁缺损4例，且较超声多检出下腹部肿块凸出3例。超声与MRI联合检查正确诊断胎儿膀胱外翻4例。盆（腹）腔内无膀胱显示，下腹壁缺损伴包块突出，脐带低置，耻骨联合分离，外生殖器畸形，肾脏和羊水量正常为产前超声及MRI诊断胎儿膀胱外翻的主要线索。

产前超声与MRI联合检查有利于明确诊断膀胱外翻，避免漏诊。

To summarized the ultrasound and MRI characteristics of fetuses with bladder exstrophy.

Four cases of bladder exstrophy (3 cases of single birth were conceived naturally, 1 twins were artificial pregnated) were diagnosed by ultrasound combined MRI which were confirmed by autopsy in Hubei Maternal and Child Heath Hospital, from February 2013 to December 2017, We summarized the ultrasonographic features of the four cases.

The common abnormal ultrasound images of the 4 cases: the bladder in the pelvic cavity was not shown, the umbilical cordinsertion was low, the symphysis pubis was separated, the gender was difficult to be determined, and the amniotic water was normal. In one case, one of the twins combined with the absence of the right kidney and abdominal wall mass below the umbilical cord insertion, and 1 case was suspected to tethered cord syndrome. Four cases of fetal antenatal MRI showed the same abnormal imaging findings as ultrasonography, but none of the 4 cases of pubic symphysis separation were showed, excluding the ultrasonographic diagnosis of tethered cord syndrome. In comparison with the X-ray and pathological examination results after the labor induction, the prenatal MRI was supplemented with 4 cases of abdominal wall defects, and 3 cases more than ultrasound. Ultrasonography and MRI combined examination were performed to correctly diagnose 4 cases of fetal bladder exstrophy. No bladder showed in pelvic nor the abdominal cavity, the abdominal wall defect with bulging content, the umbilical cord insertion was low, pubic symphysis separation, genital malformation, normal kidney andamniotic fluid were the main clues for ultrasound and MRI diagnosis of bladder exstrophy.

The combination of US and MRI can further improve the diagnostic accuracy and avoid missed diagnosis of fetal BE.