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2018-12-19  Case of the week # 492  © Fabien Ho

Answer to the case of the week # 492
March 28, 2019 - April 11, 2019

Dr Ho F.1, Dr Cuillier F.2, Dr Balu M.1

1. Radiologist, private sector, 97400 Saint-Denis, Reunion Island, France. 
2. Department of Obstetrics, Felix Guyon Hospital, Reunion Island, France.

Case report

This patient had been referred to our hospital after 2nd trimester US screening for abdominal ascites and pelvic cyst. Previous personal, familial and obstetrical history is non relevant.

Our US examination at 28 weeks of pregnancy revealed the following anomalies:

Images 1-4: - 2D and Doppler images showing fetal ascites, single umbilical artery on the right side of the bladder and behind the bladder a cystic mass with a midline septum. That cystic mass goes below the bladder neck in the pelvis, next to the femoral head. Perineal axial view revealed female genitalia. The anal muscle hypoechoic ring was missing.


Images 5 and 6: sagittal scan showing no spinal defect, the spinal cord was normal. Large bowel was not seen ahead of the vertebrae.

Images 7-10: sagittal MRI slides, in both T2 sequence and T1 sequence: from anterior to posterior : bladder (half full), cystic mass with hypoT2 debris, large bowel with rectal pouch (containing bright hyper T1 meconium) located far away from the perineal skin.

Images 11 and 12: sum up coronal and axial T1 sequence findings: the meconium appears bright and is contained in the rectal pouch way above the perineal area. Both the bladder and the cystic mass do not show meconial content.

Images 13 and 14: sum up coronal and axial T2 sequence findings: from anterior to posterior: bladder, then pelvic cystic mass with midline septum, followed by small cystic images on the upper pole, and ascites.
In a female fetus, the cystic mass is assumed to be an hydrometrocolpos with complete septum separating 2 vaginas (“big cystic mass”) and 2 uterine horns (“small cystic images on the upper poles”). The ascites is thought to be secondary to fluid leakage through tubes.

Images 15 and 16: show mild pelvic and caliceal dilation of both kidneys.

In this female fetus, the association of an anorectal malformation (high-type) + hydrometrocolpos with ascites + 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.

Therefore, a midline pelvic cystic mass which does not belong to bladder in a female fetus must raise suspicion for hydrometrocolpos and lead to look out for additional anomalies in case of a persistent Cloaca.
Other differentials may include urogenital sinus teratoma.


1. numerous articles and case showing multiples situations, slightly different on from another, leading to persistent cloaca diagnosis:

2. Nigam A, Kumar M, Gulati S. Fetal ascites and hydrometrocolpos due to persistent urogenital sinus and cloaca: a rare congenital anomaly and review of literature. (2014) BMJ case reports.

3. Yu-Peng Liu, Chih-Ping Chen. Fetal MRI of hydrometrocolpos with septate vagina and uterus didelphys as well as massive urinary ascites due to cloacal malformation. (2009) Pediatric Radiology. 39 (8): 877.

4. Subramanian Subramanian, Raju Sharma, Shivanand Gamanagatti, Sandeep Agarwala, Prerna Gupta, Sunesh Kumar. Antenatal MR diagnosis of urinary hydrometrocolpos due to urogenital sinus. (2006) Pediatric Radiology. 36 (10): 1086.

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