In this female fetus, the association of an anorectal malformation (high-type) with hydrometrocolpos, ascites, a normal bladder with mild kidney pelvic dilation led to the prenatal diagnosis of persistent cloaca.
Kidney pelvic dilation worsened on follow-up (not shown). The parents then opted for termination of the pregnancy.
A midline pelvic cystic mass which does not belong to bladder in a female fetus must raise suspicion for hydrometrocolpos and evaluation for additional anomalies in a case of a persistent cloaca.
Other differential diagnosis may include urogenital sinus teratoma.
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 Liu YP, Chen CP. Fetal MRI of hydrometrocolpos with septate vagina and uterus didelphys as well as massive urinary ascites due to cloacal malformation. Pediatr Radiol. 2009;39:877.
 Subramanian S, Sharma R, Gamanagatti S, et al. Antenatal MR diagnosis of urinary hydrometrocolpos due to urogenital sinus. Pediatr Radiol. 2006 Oct;36(10):1086-9.