An Interview with pediatric surgeon Dr. Vincent Duron
Fetal surgery is a growing area of medicine that allows pediatric patients to receive treatment before they are born. Examples of fetal surgery include minimally invasive prenatal repair of spina bifida and treatment of congenital diaphragmatic hernia using fetoscopical endoluminal tracheal occlusion (FETO).
We spoke with Vincent Pierre Duron, MD, Co-Director of Fetal Therapy, Surgical Director of the Pediatric ICU, and Director of Minimally Invasive Surgery with the Columbia University Department of Surgery/NewYork-Presbyterian/Morgan Stanley Children’s Hospital, about fetal surgery, his work and career.
What path did you take to Columbia?
It's a bit of a homecoming, since I grew up around here. My parents are French, and they moved here when I was five. For my education, I went all over: First, out west for undergrad, then back to the East Coast, where I got my general medical school training in Rochester, followed by Rhode Island for my surgery residency. Then back out to Los Angeles for critical care training, Houston for my pediatric surgery fellowship, and then back to NYC. I was looking to return to my roots, so to speak.
It was a great decision: I really like the New York area, and I love this institution. Columbia has so much to offer; its overall history and its history in pediatric surgery, the collective expertise, the collaborative environment, the culture, the faculty... it has everything you'd want.
Were you always interested in surgery?
At first, I thought I was going to pursue infectious disease or family medicine. I wanted to focus on global health. My grandfather was a military doctor in a French colony called New Caledonia, in the middle of the Pacific Ocean. It's beautiful but very remote. So he was essentially a bush doctor. He had to effectively do everything that people needed on this small island—general medicine, pediatric surgery, OB-GYN, everything. He was the one who inspired me to go into medicine.
Initially, I wanted to have a general practice, but once I had the experience of being in the operating room, I realized that I wanted to focus on surgery. My initial focus was trauma surgery, which fit in very well with global health. But towards the end of my general surgical training, I realized I wanted to work with kids. Kids are amazing. I enjoy interacting with them, speaking with them, and making them feel better. The way they approach their illness is so different than us adults; it's never really about them. They're here to get through it and to have fun. I liked that. Also, the surgical conditions that you treat in children are fascinating and challenging. So, that's why I focused on pediatric surgery.
For all that I love in general surgery—the anatomy, the dissection, the tissue handling—I also enjoy the technology and unique skill set involved in fetal surgery and how far we can go to help these patients. I'm fascinated by how we can optimize the patient's capacity to heal by intervening prenatally.
What drew you to prenatal surgery?
Fetal surgery is fantastic. It's technically challenging, and I like that challenge. And as prenatal surgeons, we get to affect diseases and surgical conditions at a very early stage and in a way that not only corrects the defect but also takes advantage of the fetus's capacity to heal. And we even help the fetus avoid additional hazards that may worsen their outcome.
For example, with myelomeningocele (MMC), a severe type of spina bifida, a portion of the spinal cord is exposed. It's a dangerous condition that can cause significant neurological and motor function issues. There's an additional challenge for these fetuses: amniotic fluid can cause inflammation to the spinal elements when directly exposed to it. So by repairing it early, before birth, we avoid this second hit, which is the toxic environment of the amniotic fluid.
For a prenatal case, a lot more preparation goes into surgery because multiple teams are involved. Since you’re operating on two patients, you have to consider both physiologies. It consists of a lot of multidisciplinary care and working with different specialties. I enjoy working with the whole team: maternal-fetal medicine specialists, neurosurgeons, plastic surgeons, and anesthesiologists. It's a great team environment where we're all working toward one cause and collaborating in a very focused way. So I enjoy that quite a bit.
How do you approach prenatal surgery for a condition like MMC?
There are three main approaches for fetal surgery for MMC: open repair, percutaneous fetoscopic repair, and fetoscopic repair with the uterus externalized.
Open repair uses a Pfannenstiel or C-section incision to externalize the uterus, make a large incision on the uterus, and repair the defect. This was the approach used in the multicenter randomized Management of Myelomeningocele Study (MOMS), the landmark study comparing outcomes between prenatal and postnatal repair for MMC. This study established the significant fetal advantages of prenatal repair.
The problem with the open repair is that the large cut on the uterus can dehisce, or split, which poses a risk to future pregnancies. In subsequent pregnancies with healthy fetuses, this uterine dehiscence can lead to complications and even death in these fetuses. So we're talking about a scenario where in a subsequent pregnancy, a healthy fetus may die because of a surgery performed on their sibling. That's a really big deal. So that is why we don't offer open repair.
Here at Columbia, we offer what's called fetoscopic repair, which is a minimally invasive surgery to access the uterus. There are two main ways of doing that. You can access the uterus percutaneously, meaning through the skin. You place the surgical instruments through a port which lets you perform the surgery inside the uterus without externalizing it.
The issue with the percutaneous approach is the risk of preterm premature rupture of the membranes (PPROM), which increases the risk of premature birth soon after the membrane rupture. PPROM is a major concern using this approach because when you're putting the port in, you may be putting pressure on the membranes—the myometrium, the endometrium, and the membranes of the uterine cavity—and those membranes can separate. If they separate, you have a higher risk of PPROM. That's why for percutaneous fetoscopic repair, the risk for PPROM can be, on average, 80%.
We take a different approach that minimizes the risks associated with open and percutaneous fetoscopic repair. We externalize the uterus using a C-section incision, similar to open repair. But we add four sutures in a box configuration to "tack up" the membranes at the site where we place the port. We think that these sutures keep the membranes from separating.
This strategy appears to decrease the risk of PPROM and the subsequent risk of delivering the fetus prematurely. It optimizes both the outcomes for the fetus in the sense that the PPROM rate is lowered, and it also allows the mom to have a vaginal birth. If you do an open repair with the large uterine incision, you are recommended to have a C-section and not a vaginal birth. The fetoscopic approach using an externalized uterus technique protects against uterine dehiscence, protecting healthy fetuses of subsequent pregnancies.
Who is part of the fetal surgery team?
Here at Columbia, we have an incredible team, and it really makes a difference. With fetoscopic repair for something like myelomeningocele, you have three main players: the maternal-fetal medicine specialist, the pediatric surgeon, and the neurosurgeon.
In some centers, the maternal-fetal medicine surgeon, or the obstetrician, does the whole case. In other centers, the neurosurgeon does the entire case. In our center, we work together throughout the surgery. Each one of us brings his/her skill set and expertise to the table and we work collaboratively to assist each other during different portions of the operation. I think that's why our results are so good: by combining our expertise, we're employing skills that we use every day on a surgery that is complex and not routine.
That's what Columbia's all about: collaborating and leveraging our strengths. Our program is successful because it highlights surgery but also involves all three specialties: pediatric surgery, maternal-fetal medicine and neurosurgery, and that's the whole point. It's nice to be around all these people who are passionate about what they're doing.
How do you determine if a fetus should have surgery for MMC?
For MMC, we follow the criteria established in the MOMS study. There are fetal requirements: the fetus needs to have a Chiari malformation, which is a sinking of the hindbrain. That defect is associated with hydrocephalus, which can require a ventriculoperitoneal shunt to remove excess cerebrospinal fluid. And the fetus needs to have the upper limit of the defect to be between the T1 and S1 vertebrae. There can't be severe kyphoscoliosis, which is a bending of the spine. There can't be chromosomal abnormalities.
The idea is that you want to intervene in cases where you have a chance to help. Between T1 and S1, the surgery can significantly impact the shunt rate and maybe also the ability to walk independently. You want to avoid placing a ventriculoperitoneal shunt because it can become obstructed or lead to infection. What was the big difference between prenatal and postnatal surgery? The shunt rate was cut in half; the MOMS trial showed that prenatal surgery was 40% compared to 80% for postnatal repair.
Our shunt rate here at Columbia is very low. We're a relatively new center, and our volume is not as high as other centers, but our outcomes are very promising. We're including the outcomes of our first ten patients as part of a manuscript we're publishing in the coming months.
Another important benefit of prenatal surgery for MMC is the reversal of hindbrain herniation, or when the brain is sinking, like the Chiari malformation I mentioned. Hindbrain herniation blocks the cerebrospinal fluid from entering the spinal canal, causing enlarged ventricles and hydrocephalus, leading to the need for a shunt. In postnatal surgery, you rarely see a reversal of that; almost all patients still have hindbrain herniation after postnatal surgery.
The MOMS study found that 63% of patients treated with prenatal surgery had a reversal of hindbrain herniation. In our series here at Columbia, all of our patients have had reversal of hindbrain herniation, which is outstanding. If you can reverse that hindbrain herniation, you have a really high chance of never needing a shunt. So it's very significant.
What does the mother need to consider for fetal surgery and recovery?
Because it's an operation not just on the fetus but on the mom and the fetus, they need a solid support system. We place a lot of emphasis on having a good support network, supportive partners, and family. You need to be vested in this surgery as the other patient because you will be getting an operation where your outcomes and the fetus's depend in part on your behavior after surgery. So you can't run a marathon because you may deliver prematurely. After surgery, we ask them not to be very active: limit driving and limit certain activities to prevent the risk of PPROM. You have to be committed to the plan.
As I mentioned, we use techniques to optimize outcomes for the fetus, mom, and subsequent pregnancies. There's less risk for the mom for things like pulmonary edema. It's a less intensive surgery because it's minimally invasive, so there's much less risk to the uterus. There's less uterine dehiscence, less thinning of the uterine scar, and less placental abruption, In this way, the risk to subsequent pregnancies is minimized. And finally, there's the chance of having a vaginal birth.
We perform MMC surgery between 22 and 26 weeks; the patients are born at our center on average at 36 weeks. It's usually a modified rest situation where they take it easy during that whole time after the procedure. And they can have a vaginal birth after that surgery.
What other conditions do you treat with fetal surgery?
I also treat a condition called congenital diaphragmatic hernia, or CDH, which occurs while the fetus is still developing in the womb. Because the diaphragm muscle doesn't form completely, it leaves an opening into the chest cavity. The intestines can move up into the chest, impairing the function and development of the lungs or even the heart.
I'm excited because we've finally gotten approval to start a new program for fetoscopic endoluminal tracheal occlusion (FETO) for CDH. We’ve worked hard to get this in place. It also involves multiple teams: the maternal-fetal medicine specialists, the pediatric surgeon, the anesthesia team, but also, very importantly, the post-op postnatal team.
FETO involves placing a balloon in the trachea of the fetus. First, the maternal-fetal medicine doctor uses a needle and ultrasound guidance to access the uterus. Then we place a scope into the fetus's mouth and trachea and deploy the balloon, which occludes, or blocks, the trachea. During development, the fetus's lungs produce fluid; with the trachea occluded, that fluid stays within the lungs and pushes against the lung tissue. This pressure causes more lung tissue to be laid down, hopefully improving lung function.
The primary morbidity in patients with CDH is that they're born with a hypoplastic lung: a small, rigid lung that doesn't exchange oxygen as well as a normal lung. By improving pulmonary outcomes, we hope to improve survival rates and overall outcomes. This procedure was studied mainly in Europe through the TOTAL (Trachea Occlusion To Accelerate Lung growth) trial, a randomized control trial led by Dr. Jan Deprest from Belgium that published its results in 2021. Now we're getting the chance to apply this technology to our patients.
After the baby is born, they're treated like any other baby with CDH: we let them stabilize, ensure they're ventilating and oxygenating well, and don't need escalating oxygen or ventilation support. Once they're stable, we surgically repair the CDH. I repair the defect minimally invasively, or thoracoscopically, when I think it is the best option for the patient. After putting the camera into the chest, depending on the size of the defect, I decide whether to continue the repair thoracoscopically or convert to an open repair. Several factors come into play for that decision to be made. Broadly speaking, for very large defects and if the patient does not tolerate the insufflation during thoracoscopy, I convert to an open approach.
Why has the FETO program taken so long to get approval?
One of the things that has complicated the effort to establish our FETO program is that in the U.S., the outcomes of patients with severe CDH are higher than both the FETO group and control group from the TOTAL study; they went from 15% survival with those who didn't have FETO to 40% survival to those with FETO, while the survival of our patients who go on ECMO here is 61%.
So we have a philosophical conundrum: our survival rate without this intervention is already better than the study cases. How do we benefit patients who already have higher survival rates than the TOTAL trial? Which is why we were studying this in a very formal and deliberate fashion.
And we think we can prevent them from having comorbidities associated with severe CDH, such as needing ECMO, long-term oxygen, and neurological development problems.
How do you determine who is a candidate for FETO?
The criteria for a patient to be a candidate for FETO in this country is to have a severe CDH, based on a lung-to-head ratio, or LHR, of less than one or an observed-to-expected lung-to-head ratio of less than 25%. This measurement compares area of the contralateral lung to the head circumference. A LHR of less than one is associated with a severe CDH, which makes them a candidate for FETO, if there are no other exclusion factors.
The observed-to-expected lung-to-head ratio is the ratio of the observed LHR compared to the expected LHR, the LHR you would expect a normal fetus without CDH to have at that gestational age.
I get involved in the planning as soon as a CDH diagnosis is confirmed. CDH can be diagnosed as early as 16 to 18 weeks. I would place the balloon at 27 weeks; because you don't want the baby to be born with the balloon in place, you remove it at 34 weeks. Studies have also found that if you leave the balloon in place too long, other types of specialized lung cells don't develop, leading to poorer outcomes.
The mother needs an amniocentesis, a cardiac echocardiogram, and usually a prenatal or fetal MRI. But there's nothing they need to do to prepare to undergo the FETO procedure. Because of the risk posed by the occlusion, they must be within a short distance of the hospital after we place the balloon in case of premature delivery.
Why is the post-natal team so crucial to FETO?
The neonatal intensive care unit (NICU) team is critical because if a baby is born early with the balloon in place, that's an emergency; because the airway is occluded, the baby can die immediately. So you need a whole team ready to puncture that balloon under ultrasound guidance or do a scope and remove the balloon after birth. And if necessary, the baby can be placed on extracorporeal membrane oxygenation, or ECMO.
Here at Columbia/NewYork-Presbyterian/Morgan Stanley Children's Hospital, we are one of only a handful of platinum centers of excellence for pediatric ECMO, which is a tremendous strength for us. It's one of the busiest centers in the country, if not the world. And our ECMO outcomes are outstanding. That's very important for patients with severe CDH because they are at increased risk of needing ECMO. So you need all that support to care for the sickest patients with CDH.
We have a long history of CDH management, a world-leading ECMO program, and a maternal-fetal medicine group with a long and robust experience in uterine access. These are only a few reasons we encourage people to come here for FETO and CDH treatment.
What do you do when you're not working?
Well, I have three daughters that my wife and I adore. I enjoy the outdoors quite a bit; we love camping. My wife and I just took my daughter and four of her friends camping in the Catskills for her birthday… it was exhausting! But a lot of fun! I love traveling. We love cooking; my wife's from Peru, so we love making Peruvian and French food. And, of course, we love eating.
We are passionate fans of Latin culture; one of my favorite artists is Juan Luis Guerra; if you like any Latin music, you should listen to him. If you don't know of him, let me tell you: he is the king.
Otherwise, I exercise to keep my spirit healthy and keep my body in working order for as long as possible. Some of our surgeries can be REALLY tough on your back!
Citations
Stewart LA, Klein-Cloud R, Gerall C, Fan W, Price J, Hernan RR, Krishnan US, Cheung EW, Middlesworth W, Chaves DV, Miller R, Simpson LL, Chung WK, Duron VP. Extracorporeal Membrane Oxygenation (ECMO) and its complications in newborns with congenital diaphragmatic hernia. J Pediatr Surg. 2022 Aug;57(8):1642-1648. doi: 10.1016/j.jpedsurg.2021.12.028.
Adzick NS, Thom EA, Spong CY, Brock JW 3rd, Burrows PK, Johnson MP, Howell LJ, Farrell JA, Dabrowiak ME, Sutton LN, Gupta N, Tulipan NB, D'Alton ME, Farmer DL; MOMS Investigators. A randomized trial of prenatal versus postnatal repair of myelomeningocele. N Engl J Med. 2011 Mar 17;364(11):993-1004. doi: 10.1056/NEJMoa1014379.
Deprest JA, Nicolaides KH, Benachi A, Gratacos E, Ryan G, Persico N, Sago H, Johnson A, Wielgoś M, Berg C, Van Calster B, Russo FM; TOTAL Trial for Severe Hypoplasia Investigators. Randomized Trial of Fetal Surgery for Severe Left Diaphragmatic Hernia. N Engl J Med. 2021 Jul 8;385(2):107-118. doi: 10.1056/NEJMoa2027030. Epub 2021 Jun 8.PMID: 34106556
Deprest JA, Benachi A, Gratacos E, Nicolaides KH, Berg C, Persico N, Belfort M, Gardener GJ, Ville Y, Johnson A, Morini F, Wielgoś M, Van Calster B, DeKoninck PLJ; TOTAL Trial for Moderate Hypoplasia Investigators. Randomized Trial of Fetal Surgery for Moderate Left Diaphragmatic Hernia. N Engl J Med. 2021 Jul 8;385(2):119-129. doi: 10.1056/NEJMoa2026983.
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