Intrahepatic portosystemic shunt: salvage mechanism for oligohydramnios complicating fetal growth restriction.

Objective: Portosystemic shunts in growth-restricted fetuses are more common than previously thought. We aimed to describe fetuses with growth restriction and transient oligohydramnios in which a congenital intrahepatic portosystemic shunt (CIPSS) was noted during follow-up.

Methods: This was a retrospective study of all fetuses diagnosed with growth restriction and transient oligohydramnios during a 5-year period in a large tertiary referral center. Our routine evaluation of growth-restricted fetuses includes monitoring of estimated fetal weight, assessment of biophysical profile, Doppler imaging, thorough examination of the umbilical-portal system and evaluation of cardiac function using fetal tricuspid annular plane systolic excursion (f-TAPSE). We compared these parameters before and after the resolution of the oligohydramnios using descriptive statistics and the Wilcoxon signed-rank test for paired non-parametric variables. During the surveillance of fetuses with transient oligohydramnios, we noted the appearance of a CIPSS and followed up such cases after birth.

Results: A total of 2144 women with a singleton pregnancy with suspected fetal growth restriction were referred to our center between January 2018 and December 2022. In 12 fetuses, oligohydramnios was evident upon initial assessment, and a CIPSS was diagnosed with normalization of amniotic fluid level. The median gestational age at diagnosis of growth restriction and oligohydramnios was 25 (range, 21-30) weeks. The estimated fetal weight was at the 1 percentile in 10/12 fetuses. The median amniotic fluid index was 5 (range, 2-5) cm at the initial appointment and improved significantly to 13 (range, 11-20) cm following the shunt diagnosis (P = 0.002). Among fetuses with f-TAPSE data available, the f-TAPSE increased significantly from 4.0 (range, 3.0-5.0) mm before the diagnosis of CIPSS to 8.0 (range, 5.0-9.4) mm following the diagnosis (P = 0.043). The median gestational age at delivery was 36.3 (range, 30.8-38.4) weeks. In nine (75%) fetuses, the diagnosed shunt was left portal to left hepatic vein. Neonatal follow-up revealed spontaneous shunt resolution within 30 months in all newborns. One newborn required embolization owing to suspected shunt, however, no shunt was detected during the procedure.

Conclusions: The development of CIPSS in growth-restricted fetuses with oligohydramnios appears to improve hemodynamic status as evidenced by normalization of amniotic fluid index and increase in f-TAPSE. Evaluation of the liver portal system in fetuses with growth restriction offers an understanding of the shunt salvage phenomenon. © 2025 International Society of Ultrasound in Obstetrics and Gynecology.