LISBON -- Methods for predicting which fetuses with congenital diaphragmatic hernia are at the greatest risk of death--and techniques for performing in utero surgery to reduce that risk--continue to emerge.
In at least one study using the latest techniques, surgeons achieved a 50% fetal survival rate with in utero surgery. That may sound rather dismal, but it is a substantial improvement over the 100% mortality among comparable controls, Dr. Jan Deprest said at a world congress sponsored by the Fetal Medicine Foundation.
Study participants comprised the most serious of the cases of diaphragmatic hernia--those with polyhydramnios before 26 weeks' gestation, right-sided disease or bilateral disease, left-sided disease plus liver herniation into the thorax, or a lung volume to head circumference ratio of less than 1, all of which are proving to be indicators of high mortality risk at leading European centers.
The surgery performed in this study involved tracheal obstruction, which has been shown to speed lung development and is also applicable to cases with liver herniation, as it "slowly releases the liver back into the abdomen," explained Dr. Deprest of Leuven, Belgium.
The entire operation is done via "key-hole" surgery, reducing the need for a hysterotomy and therefore reducing the risk for preterm contractions and obviously reducing maternal morbidity, he said.
A balloon is inserted into the trachea and "deployed," causing the obstruction. When this is done early in pregnancy, fetal lungs tend to overdevelop in terms of size but not in function, so the investigators were successful with removing the "plug" at about 34 weeks' gestation rather than after delivery.
This approach also avoids the need for an ex utero intrapartum treatment procedure.
Of 17 patients in the study, 2 had spontaneous abortions within 2 weeks of the surgery. The other 15 fetuses remained in utero for an average of 6 weeks after the procedure and had an increase in the average lung to head ratio--an indirect measure of lung development.
Still, only half of the fetuses survived, compared with none of the control fetuses with the same characteristics of those in the treatment group. Of controls that had less serious disease and did not qualify for surgery (for example, they had left-sided disease without liver herniation, which is less risky) four of six survived, he reported.
This is typical in cases of less severe disease, at least in Europe, Dr. Deprest pointed out.
Some investigators--primarily from the United States--have reported higher survival rates with in utero surgery for diaphragmatic hernia, but these results have not been reproduced in European studies. In fact, it has been difficult to compare study results, because some U.S. studies have not excluded fetuses at low risk for mortality from the treatment groups, while others have focused solely on those at the very highest risk, Dr. Deprest explained.
Much more work needs to be done to determine the best approach to his type of surgery.
The selection criteria used in his own small study must be validated, and his technique must be compared with outcomes among those treated in the standard postnatal fashion, Dr. Deprest said, adding that a simpler technique for retrieving the balloon also should be developed.
A randomized controlled trial would be useful, but it would take several years to recruit enough patients for the study to have sufficient power. A sequential study involving patients recruited over time could end earlier, however, if a clear advantage or disadvantage became apparent.
"We won't have the answers until we do this kind of trial," he said.
Creating a fetal tracheal occlusion
Surgeons have achieved a 50% fetal survival rate with in utero surgery for diaphragmatic hernia. In the surgery, which involves creating a tracheal obstruction, a latex, gold-valve balloon is deployed into the trachea and removed at a later date. This process has been shown to speed lung development, and in cases of liver hernia, to release the liver back into the abdomen.
Sources: Dr. Jan Deprest; Ultimate Visual Dictionary
[1] An extension of the fetoscope positions the balloon.
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[2] The balloon is deployed and detached in the trachea.
[ILLUSTRATION OMITTED]
SHARON WORCESTER
Tallahassee Bureau
COPYRIGHT 2003 International Medical News Group
COPYRIGHT 2003 Gale Group
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