Postoperative imaging following fetal open myelomeningocele repair: The clinical utility of magnetic resonance imaging and sonographic amniotic fluid volumes in detecting suspected hysterotomy scar dehiscence.

Abstract

Hysterotomy scar disruption, ranging from myometrial thinning to complete dehiscence, is a well-established complication of open-hysterotomy fetal myelomeningocele (MMC) repair. This study sought to (a) determine the feasibility of postoperative magnetic resonance imaging (MRI) in detecting signs of hysterotomy scar disruption and (b) identify the sonographic and clinical signs suggestive of subacute scar dehiscence, including decreasing amniotic fluid index (AFI) and uterine contractions, respectively. A unique index case of suspected hysterotomy dehiscence following MMC repair prompted a retrospective review of 31 total open-hysterotomy fetal MMC repairs performed at our center, including 21 cases found to have intact hysterotomy scarring and 10 cases of non intact scarring detected at subsequent cesarean delivery. In each case, routine post operative MRI, performed 6 weeks after the MMC repair, was reviewed to evaluate the thickness of the hysterotomy site. Cases were also reviewed for sonographic and clinical patterns preceding delivery, including changes in AFI and the presence or absence of uterine contractions. Of the 31 total reviewed cases, 21 cases were found to have intact hysterotomy scar sites at the time of cesarean delivery. Among the intact cases, the net change in AFI from the time of MRI to delivery ranged from -45% to 47%, with a mean increase in fluid levels of 8% over an average of 5.6 weeks. The other 11 cases, including the index case, were found to have signs of scar disruption at delivery, including seven with thinned scar sites and four with grossly dehiscent sites. Amongst non-intact cases, AFI predominately decreased, with a net change ranging from -56% to 9% for a mean change of -24% over an average of 5.4 weeks. Regular uterine contractions close to the time of delivery occurred in 82% of the non intact cases. Hysterotomy scar disruption can rarely be detected by MRI following MMC repair. Decreasing AFI and contractions may serve as early warning signs of scar dehiscence and should be taken into consideration for obstetric management.