Novel approach for parallelizing pairwise comparison problems as applied to detecting segments identical by decent in whole-genome data.

MOTIVATION: Pairwise comparison problems arise in many areas of science. In genomics, datasets are already large and getting larger, and so operations that require pairwise comparisons-either on pairs of SNPs or pairs of individuals-are extremely computationally challenging. We propose a generic algorithm for addressing pairwise comparison problems that breaks a large problem (of order n2 comparisons) into multiple smaller ones (each of order n comparisons), allowing for massive parallelization. RESULTS: We demonstrated that this approach is very efficient for calling identical by descent (IBD) segments between all pairs of individuals in the UK Biobank dataset, with a 250-fold savings in time and 750-fold savings in memory over the standard approach to detecting such segments across the full dataset. This efficiency should extend to other methods of IBD calling and, more generally, to other pairwise comparison tasks in genomics or other areas of science. AVAILABILITY AND IMPLEMENTATION: A GitHub page is available at https://github.com/emmanuelsapin with the code to generate data needed for the implementation.

Long-Term Functional Outcomes of an Anorectal Malformation French National Cohort.

OBJECTIVES: The present study aimed to assess long-term functional outcomes of children with anorectal malformations (ARMs) across a network of expert centers in France. METHODS: Retrospective cross-sectional study of patients ages 6-30 years that had been surgically treated for ARM. Patient and ARM characteristics (eg, level, surgical approach) and functional outcomes were assessed in the different age groups. RESULTS: Among 367 patients, there were 155 females (42.2%) and 212 males (57.8%), 188 (51.2%) cases with, and 179 (48.8%) higher forms without, perineal fistula. Univariate and multivariate statistical analyses with logistic regression showed correlation between the level of the rectal blind pouch and voluntary bowel movements (odds ratio [OR] = 1.84 [1.31-2.57], P < 0.001), or soiling (OR = 1.72 [1.31-2.25], P < 0.001), which was also associated with the inability to discriminate between stool and gas (OR = 2.45 [1.28-4.67], P = 0.007) and the presence of constipation (OR = 2.97 [1.74-5.08], P < 0.001). Risk factors for constipation were sacral abnormalities [OR = 2.26 [1.23-4.25], P = 0.01) and surgical procedures without an abdominal approach (OR = 2.98 [1.29-6.87], P = 0.01). Only the holding of voluntary bowel movements and soiling rates improved with age. CONCLUSION: This cross-sectional study confirms a strong association between anatomical status and functional outcomes in patients surgically treated for ARM. It specifically highlights the need for long-term follow-up of all patients to help them with supportive care.

Is laterality of congenital diaphragmatic hernia a reliable prognostic factor? French national cohort study.

OBJECTIVES: The objective of this study was to assess whether the laterality of congenital diaphragmatic hernia (CDH) was a prognostic factor for neonatal survival. METHODS: This was a cohort study using the French national database of the Reference Center for Diaphragmatic Hernias. The principal endpoint was survival after hospitalization in intensive care. We made a comparative study between right CDH and left CDH by univariate and multivariate analysis. Terminations and stillbirths were excluded from analyses of neonatal outcomes. RESULTS: A total of 506 CDH were included with 67 (13%) right CDH and 439 left CDH (87%). Rate of survival was 49% for right CDH and 74% for left CDH (P < .01). Multivariate analysis showed two factors significantly associated with mortality: thoracic herniation of liver (OR 2.27; IC 95% [1.07-4.76]; P = .03) and lung-to-head-ratio over under expected (OR 2.99; IC 95% [1.41-6.36]; P < .01). Side of CDH was not significantly associated with mortality (OR 1.87; IC 95% [0.61-5.51], P = .26). CONCLUSION: Rate of right CDH mortality is more important than left CDH. Nevertheless after adjusting for lung-to-head-ratio and thoracic herniation of liver, right CDH does not have a higher risk of mortality than left CDH.

Predictors of the Performance of Early Antireflux Surgery in Esophageal Atresia.

OBJECTIVE: To identify predictors of and factors associated with the performance of antireflux surgery during the first year of life in children born with esophageal atresia. STUDY DESIGN: All patients were included in a French registry for esophageal atresia. All 38 multidisciplinary French centers completed questionnaires about perinatal characteristics and one-year outcome for children born with esophageal atresia. RESULTS: Of 835 infants with esophageal atresia born in France from 2010 to 2014, 682 patients, excluding those with long-gap esophageal atresia, were included. Three patients had type I, 669 had type III, and 10 had type IV esophageal atresia. Fifty-three children (7.8%) received fundoplication during the first year of life. The median age at the time of the end-to-end esophageal anastomosis was 1.1 day (range 0-15). Multivariate analysis identified three perioperative factors that predicted the need for early antireflux surgery: anastomotic tension (P = .004), associated malformations (P = .019), and low birth weight (P = .018). Six other factors, measured during the first year of life, were associated with the need for antireflux surgery: gastroesophageal reflux (P < .001), anastomotic stricture (P < .001), gastrostomy (P < .001), acute life-threatening event (P = .002), respiratory complications (P = .045), and poor nutritional status (P < .001). CONCLUSIONS: Gastroesophageal reflux disease, low birth weight, poor nutrition, and surgical anastomosis difficulties predicted the performance of antireflux surgery in the first year of life in infants with esophageal atresia.

Long-term functional renal outcomes after retroperitoneoscopic upper pole heminephrectomy for duplex kidney in children: a multicenter cohort study.

BACKGROUND: Retroperitoneoscopic upper pole heminephrectomy (RUHN) in duplex kidney in children remains a challenging procedure with a need for postoperative functional assessment of the remnant lower pole. We aimed to calculate the incidence of long-term functional renal outcomes in these children and examine the effect of age on those outcomes. METHODS: A multicenter retrospective cohort study of 9 years included all patients undergoing RUHN and evaluated by renal ultrasound (US) and dimercaptosuccinic acid (DMSA) scintigraphy pre and postoperatively. Patients were divided in two age groups of ≤12 and >12 months. Standard follow-up assessed pre-, intra- and postoperative outcomes using clinical review, US and DMSA. RESULTS: Standard RUHN in lateral position was performed in 30 patients. Five cases were excluded (2 lacks of postoperative DMSA, 3 conversions). Indications for RUHN were non-functioning upper moieties (n = 25) caused by ureterocele (n = 11), ectopic distal implantation of the ureter with incontinence (n = 6) or evolving severe ureterohydronephrosis (n = 8). Mean age at surgery was 30 ± 27 months, operation time 116 ± 52 min and hospital stay 2.8 ± 1 days. Long-term follow-up (mean, 7.2 ± 2.7 years) with US and DMSA showed that none of the 25 patients had complete loss of lower pole renal function. Mean lower pole renal function directly related to RUHN was not significantly different after versus before RUHN for the entire cohort (n = 24; 39.7 ± 7.90 % vs. 41.7 ± 6.74 %; p = 0350), for the ≤12-month (n = 6; 39.3 ± 4.18 vs. 41.3 ± 5.47; p = 0.493) and the >12-month groups (n = 18; 39.8 ± 8.90 vs. 41.9 ± 7.25; p = 0.443). Four patients (17 %) had partial loss of function (mean function loss, 9.3 ± 5.85 %; median age, 13 months). The number and type of complications between the two age groups were not statistically different. Overall, 29 % (n = 7/24) of the patients presented with medium-term (17 %) and long-term (17 %) complications directly related to RUHN. CONCLUSIONS: RUHN is a demanding yet efficient technique that is safe for the lower pole at any age. Systematic postoperative DMSA is not mandatory as long as US remains normal.

Computing energy landscape maps and structural excursions of proteins.

BACKGROUND: Structural excursions of a protein at equilibrium are key to biomolecular recognition and function modulation. Protein modeling research is driven by the need to aid wet laboratories in characterizing equilibrium protein dynamics. In principle, structural excursions of a protein can be directly observed via simulation of its dynamics, but the disparate temporal scales involved in such excursions make this approach computationally impractical. On the other hand, an informative representation of the structure space available to a protein at equilibrium can be obtained efficiently via stochastic optimization, but this approach does not directly yield information on equilibrium dynamics. METHODS: We present here a novel methodology that first builds a multi-dimensional map of the energy landscape that underlies the structure space of a given protein and then queries the computed map for energetically-feasible excursions between structures of interest. An evolutionary algorithm builds such maps with a practical computational budget. Graphical techniques analyze a computed multi-dimensional map and expose interesting features of an energy landscape, such as basins and barriers. A path searching algorithm then queries a nearest-neighbor graph representation of a computed map for energetically-feasible basin-to-basin excursions. RESULTS: Evaluation is conducted on intrinsically-dynamic proteins of importance in human biology and disease. Visual statistical analysis of the maps of energy landscapes computed by the proposed methodology reveals features already captured in the wet laboratory, as well as new features indicative of interesting, unknown thermodynamically-stable and semi-stable regions of the equilibrium structure space. Comparison of maps and structural excursions computed by the proposed methodology on sequence variants of a protein sheds light on the role of equilibrium structure and dynamics in the sequence-function relationship. CONCLUSIONS: Applications show that the proposed methodology is effective at locating basins in complex energy landscapes and computing basin-basin excursions of a protein with a practical computational budget. While the actual temporal scales spanned by a structural excursion cannot be directly obtained due to the foregoing of simulation of dynamics, hypotheses can be formulated regarding the impact of sequence mutations on protein function. These hypotheses are valuable in instigating further research in wet laboratories.

Outcome of alimentary tract duplications operated on by minimally invasive surgery: a retrospective multicenter study by the GECI (Groupe d'Etude en Coeliochirurgie Infantile).

BACKGROUND: Alimentary tract duplications (ATD) are a rare cause of intestinal obstruction in childhood. There are many case reports but few series about laparoscopy or thoracoscopy for ATD. The aim of our study was to report the outcome of minimally invasive surgery (MIS) for ATD. METHODS: This was a retrospective multicenter study from the GECI (Groupe d'Etude en Coeliochirurgie Infantile). We reviewed the charts of 114 patients operated on by MIS for ATD from 1994 to 2009. RESULTS: Sixty-two patients (54 %) had a prenatal diagnosis. Forty-nine patients (43 %) were symptomatic before surgery: 33 of those patients (63 %) with postnatal diagnosis compared to 16 (25 %) with prenatal diagnosis (P < 0.01). In this last group, the median age at onset of symptoms was 16 days (range = 0-972). One hundred and two patients had laparoscopy (esophageal to rectal duplications) and 12 patients had thoracoscopy for esophageal duplications. The mean operative time was 90 min (range = 82-98). There were 32 (28 %) resection anastomoses, 55 (48 %) enucleations, and 27 (24 %) unroofings. The conversion rate was 32 %, and in a multivariate analysis, it was significantly higher, up to 41 % for patients weighing <10 kg (P < 0.01). Ten patients (8 %) had unintentional perioperative opening of the digestive tract during the dissection. Eight patients had nine postoperative complications, including six small bowel obstructions. The median length of hospital stay was 4 days (range = 1-21) without conversion and 6 days (range = 1-27) with conversion (P = 0.01). The median follow-up was 3 months (range = 1-120). Eighteen of the 27 patients who underwent partial surgery had an ultrasound examination during follow-up. Five (18 %) of them had macroscopic residue. CONCLUSION: This study showed that MIS for ATD is feasible with a low rate of complications. Patients with prenatal diagnosis should have prompt surgery to prevent symptoms, despite a high rate of conversion in small infants.

Anti-reflux surgery in children with congenital diaphragmatic hernia: A prospective cohort study on a controversial practice.

INTRODUCTION: Gastro-esophageal reflux disease (GERD) is the most frequent long-term morbidity of congenital diaphragmatic hernia (CDH) survivors. Performing a preventive fundoplication during CDH repair remains controversial. This study aimed to: (1) Analyze the variability in practices regarding preventive fundoplication; (2) Identify predictive factors for fundoplication. (3) Evaluate the impact of preventive fundoplication on gastro-intestinal outcomes in children with a CDH patch repair; METHODS: This prospective multi-institutional cohort study (French CDH Registry) included CDH neonates born in France between January 1st, 2010-December 31st, 2018. Patch CDH was defined as need for synthetic patch or muscle flap repair. Main outcome measures included need for curative fundoplication, tube feed supplementation, failure to thrive, and oral aversion. RESULTS: Of 762 CDH neonates included, 81 underwent fundoplication (10.6%), either preventive or curative. Median follow-up was 3.0 years (IQR: 1.0-5.0). (1) Preventive fundoplication is considered in only 31% of centers. The rates of both curative fundoplication (9% vs 3%, p = 0.01) and overall fundoplication (20% vs 3%, p < 0.0001) are higher in centers that perform preventive fundoplication compared to those that do not. (2) Predictive factors for preventive fundoplication were: prenatal diagnosis (p = 0.006), intra-thoracic liver (p = 0.005), fetal tracheal occlusion (p = 0.002), CDH-grade C-D (p < 0.0001), patch repair (p < 0.0001). After CDH repair, 8% (n = 51) required curative fundoplication (median age: 101 days), for which a patch repair was the only independent predictive factors identified upon multivariate analysis. (3) In neonates with patch CDH, preventive fundoplication did not decrease the need for curative fundoplication (15% vs 11%, p = 0.53), and was associated with higher rates of failure to thrive (discharge: 81% vs 51%, p = 0.03; 6-months: 81% vs 45%, p = 0.008), tube feeds (6-months: 50% vs 21%, p = 0.02; 2-years: 65% vs 26%, p = 0.004), and oral aversion (6-months: 67% vs 37%, p = 0.02; 1-year: 71% vs 40%, p = 0.03). CONCLUSIONS: Children undergoing a CDH patch repair are at high risk of requiring a curative fundoplication. However, preventive fundoplication during a patch repair does not decrease the need for curative fundoplication and is associated with worse gastro-intestinal outcomes in children. LEVEL OF EVIDENCE: II - Prospective Study.

Management of lower urinary tract fibroepithelial polyps in children.

INTRODUCTION: Fibroepithelial polyps (FEP) of the lower urinary tract are relatively common in adults but rare in children, with fewer than 250 cases reported in the literature to date. OBJECTIVE: The aim of this study was to address the experience of FEP management in children. STUDY DESIGN: A retrospective multicenter review was undertaken in children with defined FEP of the lower urinary tract managed between 2008 and 2018. The data at 18 pediatric surgery centers were collected. Their demographic, radiological, surgical, and pathological information were reviewed. RESULTS: A total of 33 children (26 boys; 7 girls) were treated for FEP of the lower urinary tract at 13 centers. The most common presentation was urinary outflow as hematuria (41%), acute urinary retention (25%), dysuria (19%), or urinary infections (28%). A prenatal diagnosis was made for three patients with hydronephrosis. Almost all of the children (94%) underwent ultrasound imaging of the urinary tract as the first diagnostic examination, 23 (70%) of them also either had an MRI (15%), cystourethrography (25%), computerized tomography (6%), or cystoscopy (45%). Two of these children (6%) had a biopsy prior to the surgery. The median preoperative delay was 7.52 (range: 1-48) months. Most of the patients were treated endoscopically, although four (12.1%) had open surgery and two (6.1%) had an additional incision for specimen extraction. The median hospital stay was 1.5 (range: 1-10) days. There were no recurrences and no complications after a median follow-up of 13 (range: 1-34) months. DISCUSSION: The main limitation of our study is the retrospective design, although it is the largest one for this pathology. CONCLUSION: This series supports sonography as the most suitable diagnosis tool before endoscopy to confirm the diagnosis and to perform the resection for most FEP in children. This report confirms the recognized benign nature in the absence of recurrences. LEVEL OF EVIDENCE: Level V.

Esophageal Atresia and Respiratory Morbidity.

BACKGROUND AND OBJECTIVES: Respiratory diseases are common in children with esophageal atresia (EA), leading to increased morbidity and mortality in the first year. The primary study objective was to identify the factors associated with readmissions for respiratory causes in the first year in EA children. METHODS: A population-based study. We included all children born between 2008 and 2016 with available data and analyzed factors at birth and 1 year follow-up. Factors with a P value <.10 in univariate analyses were retained in logistic regression models. RESULTS: Among 1460 patients born with EA, 97 (7%) were deceased before the age of 1 year, and follow-up data were available for 1287 patients, who constituted our study population. EAs were Ladd classification type III or IV in 89%, preterm birth was observed in 38%, and associated malformations were observed in 52%. Collectively, 61% were readmitted after initial discharge in the first year, 31% for a respiratory cause. Among these, respiratory infections occurred in 64%, and 35% received a respiratory treatment. In logistic regression models, factors associated with readmission for a respiratory cause were recurrence of tracheoesophageal fistula, aortopexy, antireflux surgery, and tube feeding; factors associated with respiratory treatment were male sex and laryngeal cleft. CONCLUSIONS: Respiratory morbidity in the first year after EA repair is frequent, accounting for >50% of readmissions. Identifying high risk groups of EA patients (ie, those with chronic aspiration, anomalies of the respiratory tract, and need for tube feeding) may guide follow-up strategies.

From Optimization to Mapping: An Evolutionary Algorithm for Protein Energy Landscapes.

Stochastic search is often the only viable option to address complex optimization problems. Recently, evolutionary algorithms have been shown to handle challenging continuous optimization problems related to protein structure modeling. Building on recent work in our laboratories, we propose an evolutionary algorithm for efficiently mapping the multi-basin energy landscapes of dynamic proteins that switch between thermodynamically stable or semi-stable structural states to regulate their biological activity in the cell. The proposed algorithm balances computational resources between exploration and exploitation of the nonlinear, multimodal landscapes that characterize multi-state proteins via a novel combination of global and local search to generate a dynamically-updated, information-rich map of a protein's energy landscape. This new mapping-oriented EA is applied to several dynamic proteins and their disease-implicated variants to illustrate its ability to map complex energy landscapes in a computationally feasible manner. We further show that, given the availability of such maps, comparison between the maps of wildtype and variants of a protein allows for the formulation of a structural and thermodynamic basis for the impact of sequence mutations on dysfunction that may prove useful in guiding further wet-laboratory investigations of dysfunction and molecular interventions.

Ant colony optimisation of decision tree and contingency table models for the discovery of gene-gene interactions.

In this study, ant colony optimisation (ACO) algorithm is used to derive near-optimal interactions between a number of single nucleotide polymorphisms (SNPs). This approach is used to discover small numbers of SNPs that are combined into a decision tree or contingency table model. The ACO algorithm is shown to be very robust as it is proven to be able to find results that are discriminatory from a statistical perspective with logical interactions, decision tree and contingency table models for various numbers of SNPs considered in the interaction. A large number of the SNPs discovered here have been already identified in large genome-wide association studies to be related to type II diabetes in the literature, lending additional confidence to the results.

Management of simple renal cyst in children: French multicenter experience of 36 cases and review of the literature.

OBJECTIVE: The widespread use of renal ultrasonography has resulted in simple renal cysts (SRC) being discovered with increasing frequency in routine pediatric urological practice. Management of SRC, however, remains controversial. Most SRC are asymptomatic, are diagnosed incidentally, and have no clinical consequence. Our goal was to focus on management strategies for SRC in children with the support of our experience and a review of the literature. MATERIALS AND METHODS: A literature review was made of SRC in children since 1950, analyzing epidemiologic data, diagnosis, and management. In addition, a retrospective multicenter study was conducted from 1998 to 2009. Patients included presented with a unique SRC. Data recorded were patient characteristics (age, gender), symptoms, imaging features of the cyst (size, side, pole, and location), type of management, and long-term outcomes. To focus on management, two groups of patients were defined: primary surgical management and primary conservative management consisting of clinical and US follow-up. Our results were compared with the literature. RESULTS: Thirty-six cases were included. Fifteen patients were symptomatic. Comparing the two groups, long-term outcomes were similar. The only significant factors were preoperative (age of the patient, diameter and location of the cyst): the bigger the cyst, the more likely it was to be exorenal, and the greater the likelihood that surgery would be performed (p = 0.006). Symptoms were not a significant indicator for surgery. CONCLUSION: According to the literature and our experience, and considering the benign natural history of SRC and the similar outcomes whatever the treatment, primary conservative management is recommended for all cases. Surgery should be restricted to symptomatic large compressive cysts, increase in cyst size on follow-up, and uncertain diagnosis. Percutaneous cyst aspiration with sclerotherapy has not yet been used enough to ascertain its safety, and requires prospective evaluation.

Inguinal hernia in premature boys: should we systematically explore the contralateral side?

OBJECTIVE: Bilateral surgery has been largely advocated in premature boys with unilateral inguinal hernia owing to the high incidence of contralateral patent processus vaginalis. Recently, the potential morbidity of herniotomy in low birth-weight babies and the progress in pediatric anesthesia questioned this attitude. This study aims to evaluate the incidence of contralateral metachronous hernia in a large series of premature boys and to compare the morbidity of preventive versus elective surgery. METHODS: This retrospective multicenter analysis of 964 premature boys presenting with unilateral inguinal hernia operated from 1998 to 2012 included 557 infants who benefited from a unilateral herniotomy and 407 from a bilateral herniotomy (median follow-up 12months). RESULTS: Contralateral metachronous hernia after unilateral surgery occurred in 11% (n=60) without significant difference according to the initial symptomatic side (9.5% on right vs 13% on left, p>0.05). Postoperative morbidity on the contralateral side was higher after preventive surgery than elective surgery with metachronous hernia (2.45% versus 0.9%, p=0.05) especially for secondary cryptorchidism (1% vs 0%, p=0.03). Despite the risk of metachronous incarcerated hernia, elective surgery did not increase the rate of testicular hypotrophy on the opposite side (0.7%, vs 0.7%, p>0.05). CONCLUSION: Systematic bilateral herniotomy is unnecessary in almost 90% of patients and has a significant morbidity. Secondary surgery for metachronous hernia does not increase the risk of testicular lesion and even reduces the risk of secondary cryptorchidism. These results, along with the risk of hypofertility reported after bilateral surgery, may justify treating only the symptomatic side in premature boys.

Esophageal atresia: data from a national cohort.

PURPOSE: A prospective national register was established in 2008 to record all new cases of live-birth newborns with esophageal atresia (EA). This epidemiological survey was recommended as part of a national rare diseases plan. METHODS: All 38 national centers treating EA participated by completing for each patient at first discharge a questionnaire validated by a national committee of experts. Data were centralized by the national reference center for esophageal anomalies. Quantitative and qualitative analyses were performed, with P-values of less than 0.05 considered statistically significant. Results of the 2008-2009 data collection are presented in this report. RESULTS: Three hundred seven new living cases of EA were recorded between January 1, 2008, and December 31, 2009. The male/female sex ratio was 1.3, and the live-birth prevalence of EA was 1.8 per 10,000 births. Major characteristics were comparable to those reported in the literature. Survival was 95%, and no correlation with caseload was noted. CONCLUSIONS: Epidemiologic surveys of congenital anomalies such as EA, which is a rare disease, provide valuable data for public health authorities and fulfill one important mission of reference centers. When compared with previous epidemiological data, this national population-based registry suggests that the incidence of EA remains stable.

Ectopic extralobar pulmonary sequestrations in children: interest of the laparoscopic approach.

BACKGROUND: Extralobar pulmonary sequestrations (EPS) are a rare benign congenital bronchopulmonary foregut malformation. Complete resection is necessary to confirm the diagnosis with histopathologic examination. The aim of this study was to describe the laparoscopic minimally invasive surgery (MIS) for a small series of ectopic EPS in small children and to show its feasibility and safety. METHODS: From January 2001 to December 2008, 12 cases of EPS were prenatally diagnosed and retrospectively reviewed. From this group, we isolated 6 children with ectopic EPS. Ages ranged from 15 days to 14 months. Three infants were symptomatic, and the others showed persistence of the lesion with parental anxiety. All prenatal diagnoses were confirmed by postnatal Doppler ultrasound and intravascular contrast computed tomography scan with 3-dimensional reconstructions. Postnatally, all were ectopic lesions: 3 were hiatal and intradiaphragmatic, 3 infradiaphragmatic and left paramedian. Laparoscopic MIS consisted of 4 small trocars and low-pressure pneumoperitoneum. We carried out a retroesophageal dissection in 4 cases, an elective control of systemic vessels, and a removal of the EPS with histologic study. RESULTS: We performed 5 procedures laparoscopically and 1 thoracoscopically. There were 2 abdominal conversions. Nevertheless, no intraoperative or immediate postoperative complications occurred. Hospital stay ranged from 1 to 5 days (mean, 2.7 days). The diagnosis of pure pulmonary sequestration with feeding vessels in 5 cases was confirmed by histopathology. Follow-up ranged from 13 to 84 months (mean, 43 months). Late complications were benign. CONCLUSIONS: Laparoscopic MIS for ectopic EPS in small children is a feasible and safe technique. The great magnification provided by the endoscopic procedure allows for the search of associated congenital anomalies, meticulous retroesophageal dissection, and control of the systemic vessels. Resection provides definitive diagnosis and treatment, and confers the benefits of a minimal access technique.

Patent ductus arteriosus ligation: the LigaSure system may be unreliable.

Surgical ligation of a patent ductus arteriosus (PDA) in small premature infants may be performed with open thoracotomy or video-assisted thoracoscopic surgery (VATS). The LigaSure vessel sealing system (Valleylab/Tyco Healthcare, Boulder, CO) is increasingly being used because of its effectiveness in promoting coagulation. Moreover, for PDA ligation using VATS, the LigaSure system seems more practical than vascular clips. Among 81 children, including 43 premature infants weighing less than 1000 grams operated on for PDA in our institution, one 9-month-old boy weighing 7600 grams underwent PDA ligation using a LigaSure grasp. The perioperative aspect of the closed ductus was satisfactory. The following day, however, ultrasound control revealed recanalization of the ductus, and the child had to undergo a second operation. At operation, the ductus wall adventia and media appeared to have retracted to both extremities, leaving the intima exposed and pulsating under the blood pressure. The PDA ligation was repeated, but in conditions of severe hemorrhage. The LigaSure system works by fusing collagen in the tissue. However, because the ductus wall has less collagen than any other vessels in the body, the LigaSure vessel sealing system is not reliable for PDA ligation.