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.