Presentation
Incidental finding on second trimester screening.
Patient Data
Image 1,2,3,4 sum up an axial scan
- Fetal ascites, E: Stomach.
- Single umbilical artery on the right side of the bladder: behind the bladder, there is a cystic mass with a midline septum.
- The cystic mass goes below the bladder neck in the pelvis, next to the femoral head.
- Perineal axial view reveals female genitals. The anal muscle hypoechoic ring is interestingly missing.
Images 5 and 6 sum up a sagittal scan: No spinal defect is seen, the spinal cord is normal. Large bowel is not seen ahead of the vertebrae.
Sagittal MRI slides, in both T2 sequence and T1 sequence: From anterior to posterior: bladder (half full), cystic mass with hypoT2 debris, then large bowel with rectal pouch (containing bright hyperT1 meconium) located far away from the perineal skin.
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.
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.
The last image shows mild pelvic and caliceal dilation of both kidneys.
Case Discussion
In this female fetus, the association of an anorectal malformation (high-type) and hydrometrocolpos with ascites and normal bladder with mild kidney pelvic dilation led to the prenatal diagnosis of a persistent cloaca. Kidney pelvic dilation worsened on follow-up (not shown)
Therefore, a midline pelvic cystic mass which does not belong to the bladder in a female fetus must raise suspicion for hydrometrocolpos and lead to searching for additional anomalies in case of a persistent cloaca. Other differentials may include urogenital sinus teratoma.
One should bear in mind that a persistent cloaca encompasses a large spectrum of anomalies. There have been several other forms of cloaca reported in the literature.
Dr Fabrice Cuillier and Dr Marie Balu also contributed to this case.