Thoracoamniotic shunting is the treatment of choice for management of the fetus with symptomatic fetal hydrothorax (FHT) before 32 weeks of gestation. In contrast, thoracentesis is a diagnostic maneuver performed to obtain pleural fluid for differential cell count and viral culture to establish whether the effusion is chylous.
Even repeated thoracentesis usually provides inadequate decompression of the fetal chest. There have been several reports of thoracentesis for fetal hydrothorax performed with either complete resolution or a good outcome despite reaccumulation.
Others have had disappointing results with repeated thoracentesis for fetal hydrothorax, owing to rapid reaccumulation of the effusion and neonatal death from respiratory insufficiency. Spontaneous resolution of fetal hydrothorax may occur in as many as 10% of cases, and resolution following thoracentesis may or may not be related to the procedure.
In general, thoracentesis alone cannot provide continuous decompression of the fetal chest to allow pulmonary expansion and prevent pulmonary hypoplasia.
Thoracoamniotic shunting for fetal hydrothorax, first reported by Rodeck and colleagues in 1988, provides continuous decompression of the fetal chest, allowing lung expansion. If instituted early enough, this procedure allows compensatory lung growth and may prevent neonatal death from pulmonary hypoplasia.
The indications for thoracoamniotic shunting are not well defined. Most authors consider the presence of fetal-hydrothorax-induced hydrops or polyhydramnios as indications for shunting. In addition, we recommend thoracoamniotic shunting for primary fetal hydrothorax with evidence of effusion under tension even in the absence of hydrops.
Because spontaneous resolution has been observed in even severe cases of fetal hydrothorax, we reserve thoracoamniotic shunting for cases in which tension hydrothorax recurs after two thoracenteses.
Thoracoamniotic shunts have also been used in the treatment of congenital cystic adenomatoid malformation (CCAM) of the lung with a dominant cyst. Nicolaides and associates reported the first case of CCAM treated by shunt insertion in utero in 1987.
Decompression of a large type I CCAM in a fetus of 20 weeks' gestation by percutaneous placement of a thoracoamniotic shunt was subsequently reported by Clark in 1987. This procedure resulted in resolution of both mediastinal shift and hydrops and successful delivery at 37 weeks of gestation.
Postnatally, the infant underwent uneventful resection of the CCAM. Six subsequent cases of thoracoamniotic shunting in CCAM have been reported by Adzick and coworkers, with a good outcome in five of the six fetuses treated.
Recently, Wilson et al, updated this single center's experience with 10 cases of thoracoamniotic shunting for CCAMs. There was a 51% reduction in the CCAM volume immediately after the placement of the thoracoamniotic shunt. Seven of the 10 fetuses treated by thoracoamniotic shunt survived.
More commonly, it is the type III CCAM, or microcystic lesions that become enlarged, resulting in hydrops and intrauterine fetal demise. In these later cases open fetal surgery and resection are indicated. However, in the rare instances in which there is a single large cyst in CCAM responsible for hydrops, thoracoamniotic shunting is the treatment choice.