Prenatal diagnosis of bladder exstrophy by fetal MRI

PURPOSE: To review our experience with prenatal diagnosis of bladder exstrophy by fetal magnetic resonance imaging (MRI). Bladder exstrophy can be diagnosed by ultrasonography (US) evaluation of the fetus based on absence of bladder filling, low-set umbilicus, small genitalia and lower abdominal mass, although in some instances more accurate anatomical information is desired. MATERIAL AND METHODS: We studied three patients at mean gestational age of 27.3 weeks. The fetal MRI exam was performed on axial, sagittal, coronal planes and echo gradient in the best plan for acquisition of fetus. Images were analyzed by a group of three radiologists with experience in fetal MRI. RESULTS: The MRI defined a lower abdominal mass prolapsing below the umbilical vessels, having the ureters ending on it in an anterior position. A cloacal malformation or a cloacal exstrophy could be excluded, as well as other accompanying spinal abnormalities. The renal system and oligohydramnios could be well documented. CONCLUSIONS: The MRI showed a detailed scenario of the abnormality with advantages over the US evaluation in regard to excluding cloacal anomalies. MRI allowed accurate sexual differentiation and may be indicated after suspected bladder exstrophy on US evaluation.