What--and why--the pediatric surgeon should know about twin-to-twin transfusion syndrome

Towards Placental Surface Vasculature Exploration in Virtual Reality

We present a case study evaluating the potential for interactively identifying placental surface blood vessels using magnetic resonance imaging (MRI) scans in virtual reality (VR) environments. We visualized the MRI data using direct volume rendering in a high-fidelity CAVE-like VR system, allowing medical professionals to identify relevant placental vessels directly from volume visualizations in the VR system, without prior vessel segmentation. Participants were able to trace most of the observable vascular structure, and consistently identified blood vessels down to diameters of 1 mm, an important requirement in diagnosing vascular diseases. Qualitative feedback from our participants suggests that our VR visualization is easy to understand and allows intuitive data exploration, but complex user interactions remained a challenge. Using these observations, we discuss implications and requirements for spatial tracing user interaction methods in VR environments. We believe that VR MRI visualizations are the next step towards effective surgery planning for prenatal diseases.

What-and why-the pathologist should know about twin-to-twin transfusion syndrome

Approximately 20% of all twin pregnancies are monochorionic. Between 9% and 15% of all monochorionic twin gestations are complicated by severe chronic twin-to-twin transfusion syndrome (TTTS), characterized by a gradual shift of blood volume from the donor twin to the recipient twin through placental vascular connections [1 - 3] . The prognosis of severe, untreated chronic TTTS diagnosed in midtrimester fetuses is extremely poor, with mortality rates exceeding 70% [4] . Since publication of the results of the Eurofoetus trial in 2004, laser photocoagulation of the intertwin anastomoses has become accepted as the optimal first-line therapy for severe TTTS diagnosed before 26 weeks of gestation. While laser treatment of vascular communications was initially limited to selected fetal treatment centers, its increasingly widespread use has resulted in the exposure of more pathologists, even in less specialized institutions, to laser-treated placentas. Furthermore, the surge in laser coagulation has revived the general medical, scientific, and public interest in the placental and choriovascular findings in monochorionic twin placentas. The pathologist's understanding of the pathophysiology of TTTS and of TTTS-associated placental pathology, including the findings related to laser ablation of the anastomoses, can be of great benefit to the involved obstetric/neonatal/surgical team and, ultimately, to the patients. In this review, we summarize the current knowledge of the placental contributions to TTTS and other complications of monochorionic twinning and describe the strengths and limitations of placental examination in these settings. It is our expectation that overviews such as this may serve as a template to generate consensus guidelines for standardized and evidence-based pathologic evaluation of monochorionic twin placentas.

Long-term morbidity after fetal endoscopic surgery for severe twin-to-twin transfusion syndrome

BACKGROUND/PURPOSE

Severe twin-to-twin transfusion syndrome (TTTS) leads to 80% to 100% dual mortality. Endoscopic laser coagulation of connecting vessels improves outcome to 80% survival of at least 1 twin. There is limited long-term follow-up of surviving TTTS patients. The aim of this study was to analyze gestational age-stratified, long-term morbidity in these patients.

METHODS

A retrospective case-control study of TTTS surviving patients (38 patients, 72% follow-up rate) from one center. Perinatal and pediatric records were reviewed, and outcomes were compared with published reports and gestational age-matched controls.

RESULTS

Forty percent (15/38) had at least 1 major sequela, all but 6 of which were fully resolved at a median follow-up of 4.4 years. There were no permanent cardiac, genitourinary, renal, or respiratory sequelae. All major complications were in patients born <29 weeks. There were no significant differences in complications between this cohort of patients and gestational age (GA)-matched control patients.

CONCLUSIONS

The long-term morbidity of monochorionic twins after fetal laser surgery for severe TTTS is 13%. At a median follow-up of more than 4 years, these children fare no worse than gestational age-matched, non-operated twins and singletons. The degree of prematurity at birth is the best predictor of temporary or permanent sequela in this group of patients.

Reflectance spectrometry for real-time hemoglobin determination of placental vessels during endoscopic laser surgery for twin-to-twin transfusion syndrome

OBJECTIVE

The objective of the study was to develop a noninvasive technique to determine hemoglobin (Hb) content through spectral analysis of diffusely reflected broadband visible illumination from individual blood vessels during endoscopic fetal surgery for twin-to-twin transfusion syndrome (TTTS).

METHODS

The reflection of an incoming xenon endoscopic light source was captured through a 630-mum-diameter optic fiber coupled to a fixed grating spectrometer (2-nm resolution). A 450- to 700-nm wavelength range was used for analysis. Three data-capturing methods were studied: (1) fixed-image spectrum capture with fiber aimed at (but not touching) center of a vessel, (2) no-touch scanning perpendicular to the vessel and dynamic spectral capture, and (3) dynamic spectral capture and analysis of the reflectance spectra during brief vessel touch.

RESULTS

Eight controls (elective laparoscopic and thoracoscopic operations in children aged 1-17 years) were enrolled. Four vessels were analyzed in each case. The brief-touch technique with intensity peak analysis yielded the most reproducible results between multiple vessels in the same patient. Spectrometry was also applied to 2 TTTS patients. The (anemic) donor and (polycythemic) recipient twin fetuses could be differentiated with good correlation between vessels (arteries and vein) of the same fetus.

CONCLUSIONS

It is possible to differentiate donor from recipient placental vessels by spectral analysis of the reflected light through the endoscope using a noninvasive and real-time method. This may improve the accuracy of endoscopic laser ablation of placental vessels in TTTS and may allow instant endoscopic Hb determination for laparoscopic procedures as well.

Intestinal complications after antenatal fetoscopic laser ablation in twin-to-twin transfusion syndrome

Twin-to-twin transfusion syndrome (TTTS) occurs in 9% of monochorionic twin pregnancies. An imbalanced blood flow across placental vascular communications produces a hypovolemic condition in the donor fetus and hypervolemia in the recipient fetus, leading to a variety of postnatal complications. We report 3 cases of intestinal injury in TTTS after fetoscopic laser ablation of the communicating vessels: 2 cases of intestinal atresia, and 1 case of necrotizing enterocolitis of 1 twin. Intestinal ischemic diseases have been reported after prenatal laser treatment in TTTS; with this report, we add 3 more cases.

The pediatric surgeons' contribution to in utero treatment of twin-to-twin transfusion syndrome

OBJECTIVE

To evaluate the outcome of twin-to-twin transfusion syndrome (TTTS) treated using a combination of endoscopic fetal surgery-specific techniques and surgical restraint.

SUMMARY BACKGROUND DATA

TTTS is a condition of identical twins that, if progressive and left untreated, leads to 100% mortality. The best treatment option is obliteration of the intertwin placental anastomoses, but fetal surgery carries significant maternal and fetal risks. Even if successful, percutaneous endoscopic laser ablation of placental vessels (LASER) causes premature rupture of membranes (PROM) in 10% to 20% of pregnancies. Patient selection is particularly critical because the progression of the disease is unpredictable. This has prompted many to intervene early, yielding survival rates of >=1 twin of 75% to 80%.

METHODS

We developed a minimally invasive approach to fetal surgery, a unique membrane sealing technique and a conservative algorithm that reserves intervention for severe TTTS. Pregnancies with TTTS (stages I-IV) managed in the last 8 years were reviewed. LASER was offered in stage III/IV only.

RESULTS

Ninety-eight cases of TTTS were managed in a pediatric surgery/maternal-fetal medicine collaborative Fetal Treatment Program-39 were observed (40%) and 59 underwent LASER (60%). Survival of >= twin was seen in 82.7%, and overall survival was 69.4%. These survival rates are similar to, or better than, other comparable series with similar stage distribution (low:high stage ratio 1:1) in which all patients underwent LASER. PROM rate was 4%.

CONCLUSIONS

Reserving LASER treatment for severe TTTS results in outcomes similar to, or better than, LASER for all stages. Applying fetal surgery-specific endoscopic techniques, including port-site sealing, reduces postoperative complications.

Twin-to-twin transfusion syndrome: a comprehensive update

Twin-to-twin transfusion syndrome (TTTS) is a serious complication in about 10% to 20% of monozygous twin gestations with an incidence of 4% to 35% in the United States. Severe TTTS is reported to occur in 5.5% to 17.5% of cases. TTTS is a progressive disease in which sudden deteriorations in clinical status can occur, leading to death of a co-twin. Up to 30% of survivors may have abnormal neurodevelopment as a result of the combination of profound antenatal insult and the complications of severe prematurity. This article presents an overview of what is known about the pathophysiology and the diagnosis of TTTS, the role of echocardiography in TTTS, treatment options available for TTTS, complications of treatment for TTTS, and short- and long-term outcomes of TTTS.

Survival after laser surgery for twin-to-twin transfusion syndrome: when are they out of the woods?

PURPOSE

Severe, progressive twin-to-twin transfusion syndrome (TTTS) is associated with near-100% mortality if left untreated. Endoscopic laser ablation of placental vessels (ELA) is associated with 75% to 80% survival of at least one twin. The actuarial risk of fetal demise after ELA has not yet been described.

STUDY DESIGN

A retrospective cohort study from 2 centers on a consecutive series of 163 sets of monochorionic twins with severe TTTS (18 Quintero stage I, 55 stage II, 71 stage III, 19 stage IV) who underwent ELA. Actuarial survival was calculated and stratified for donor vs recipient and according to stage.

RESULTS

Median gestational age at diagnosis was 20.1 weeks; median operative time was 60 minutes. Overall survival was 63%, and survival of at least one twin was seen in 76% of pregnancies. Of fetal demises, 10% occurred within 48 hours after ELA, and 90% of all fetal demises occurred within 1 month. There was a 10% survival advantage of recipients over donors. Survival was similar for stages I, II, and IV (75%-80%), compared with 55% for stage III.

CONCLUSIONS

Actuarial survival curves for TTTS confirms a greater burden on donor than on recipient but not at a previously reported 2:1 ratio. The current staging system does not accurately reflect post-ELA mortality risk. The unexpected higher mortality in stage III may reflect a more acute progression of the disorder in this group, an adverse effect of LA on an as yet unknown subgroup with stage III or, alternatively, preoperative demise of fulminant stage IV patients, leaving a stage IV subgroup with a more benign course and better outcome.

Twin-Twin Transfusion Syndrome Modeling

The twin-twin transfusion syndrome (TTTS) is a severe complication occurring in monochorionic twins, and untreated, causes high rates of mortality and morbidity. In TTTS, five consecutive stages of increasing severity can be distinguished: first, the oligopolyhydramnios sequence; second, anuria in the donor twin; third, abnormal flow waves in either twin; fourth, a hydropic recipient, and finally the fifth stage, fetal demise of either twin. Recently, we developed a mathematical model of the Stages I-IV. In this report, we investigated the influence of amnioreduction and laser therapy at two different gestational ages on the resolution of TTTS Stage III. Simulations were performed for two gestational ages, at 22 and 28 weeks; that is, at the onset of a stuck donor twin and when TTTS has progressed to an anuric donor with abnormal umbilical flow waves and a hydropic recipient, respectively. Results indicate abnormal umbilical flow waves in the donor to resolve rapidly after both amnioreduction and laser therapy. TTTS and abnormal umbilical flows in the donor, however, return after amnioreduction. Laser therapy, leading to cessation of fetofetal transfusion, produces complete resolution of TTTS sequelae, however, with increased vascular stiffness in the donor. Amnioreduction and laser therapy both produce rapid resolution of abnormal umbilical flows in a mathematical model of TTTS. Laser ablation of all anastomoses, however, completely ceases the fetofetal transfusion, so that no TTTS redevelops. In the donor, vascular stiffness remains increased after laser, suggesting increased pulse wave velocities can be measured clinically.

Port insertion and removal techniques to minimize premature rupture of the membranes in endoscopic fetal surgery

BACKGROUND

Premature rupture of membranes (PROM) remains a significant complication of fetal surgery. Rates of 40% to 100% have been reported after both open and endoscopic fetal surgery. We describe a technique of endoscopic port insertion and removal that minimizes trauma to the membranes.

METHODS

Twenty-seven consecutive patients undergoing endoscopic laser ablation for twin-to-twin transfusion syndrome were reviewed. In each case, a minilaparotomy was performed, and the amniotic cavity was entered under direct vision of the uterus using a Seldinger technique. The entry site was carefully dilated to accommodate a 4.0-mm-diameter cannula. A gelatin sponge plug was placed at port removal. Postoperative management and outcome were evaluated.

RESULTS

Median gestational age at operation was 21.3 weeks. Median operating time was 60 minutes. One patient delivered intraoperatively because of fetal distress. Seventeen (65.4%) patients required postoperative tocolysis (median duration, 12 hours). Median postoperative gestation was 6.5 weeks (range, 1-20 weeks). Only 1 (4.2%) of 24 patients with successful gelatin sponge placement developed PROM.

CONCLUSIONS

Meticulous technique and atraumatic insertion and removal of ports help minimize the risk of postoperative amniotic leak after endoscopic fetal surgery. Our PROM rate of 4.2% contrasts sharply with previously reported rates after similar operations.