• fetal abdominal cysts
• prenatal diagnosis
• ultrasound

A wide variety of cysts can be detected in the fetal abdomen and does not represent an uncommon finding at routine sonography. Cysts can originate from any intra-abdominal structure, even if most of them belong to the renal tract. Regardless of the underlying pathology, the typical sonographic presentation is that of a round, mainly anechoic structure of variable size, number and position within the fetal abdomen.
This series describes a single centre’s experience in diagnosis and follow-up of fetuses with an intra-abdominal cyst that were detected or addressed to our referral hospital over 22 years. During this period, we collected a total of 100 cases. We excluded from this data collection the masses that at the first scan appeared to belong to the renal tract. The prenatal sonographic diagnosis were: 42 ovarian cysts, 23 dilated bowel loops (7 of which at the duodenal level), 15 umbilical vein varices, 3 choledochal cysts and 6 single cases associated to major anomalies. The remaining 11 cases could not be classified until delivery or longer. Fetuses were scanned approximately every two weeks until delivery or disappearance of the image.
Most of these cysts were first detected in the third trimester. The latest diagnosis was that of ovarian cysts, with only one case of early detection at 20 weeks. Out of 35 cases with a complete follow-up, 10 persisted after delivery and 5 were surgically removed. The double bubble sign was detected in the third trimester 6 times out of seven cases, and among them two fetuses died in utero, while a fetus was affected by trisomy 18 and died a few days after birth. The remaining 4 cases underwent surgery and between them one was affected by trisomy 21 ond one other had a Meckel’s diverticulum and a bifid thumb associated with the duodenal atresia. Out of the remaining dilated bowel loops suspects, 3 were confirmed after delivery, one died in utero, one was diagnosed with a congenital chloride diarrhea and one died when she was two months old and a Jeune’s syndrome was suspected. The others had disappeared during prenatal scans or they were normal anatomic variant of bowel loops. Between the fifteen umbilical vein varices 13 were isolated, and the newborns were alive and well. In our case records three cysts were considered to belong to the choledocus: two disappeared during the prenatal follow up and one was still detectable at birth with no sign of biliary atresia. Among the rarer diagnosis, we collected some fetal tumors (hepatic hamartoma, hepatic cavernous hemangioma, sacrococcygeal teratoma, lymphangioma) and some complex syndromes. These pathologies were detected in the mid trimester.
Especially intriguing was the finding of 11 abdominal cysts of unclear origin at diagnosis. Five disappeared during the prenatal follow- up, and among these one fetus subsequently died in utero and no abdominal cyst was found at autopsy; on the contrary, one cyst was not detected at neonatal sonography, but four months later an enteric duplication was found and the baby underwent surgery. Among those that were still detectable at the last prenatal scan one had meconium peritonitis and one had a complex syndrome with the cyst ascribable to a hydrometrocolpos.
Among 100 patients, 5 requested termination of pregnancy because of the detection of associated major anomalies, while five fetuses died spontaneously in utero (2 duodenal atresias, 1 jejunum obstruction, 1 hepatic cavernous hemangioma and the above mentioned cyst disappeared during prenatal scans). Three babies died after delivery because of major syndromes (a trisomy 18, a cloacal anomaly and a Jeune’s syndrome).
Our findings support the importance of the routine third trimester ultrasound scan, in fact both a planned delivery and a prompt intervention after delivery might be relevant to treat some of the underlying pathology. Moreover our findings support the importance of a close surveillance of both the fetus and the newborn even when the images are no longer detected during pregnancy or at birth.