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^st 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.