Simon Clarke

Recovery after open versus laparoscopic pyloromyotomy for pyloric stenosis: a double-blind multicentre randomised controlled trial

BACKGROUND A laparoscopic approach to pyloromyotomy for infantile pyloric stenosis has gained popularity but its effectiveness remains unproven. We aimed to compare outcomes after open or laparoscopic pyloromyotomy for the treatment of pyloric stenosis. METHODS We did a multicentre international, double-blind, randomised, controlled trial between June, 2004, and May, 2007, across six tertiary paediatric surgical centres. 180 infants were randomly assigned to open (n=93) or laparoscopic pyloromyotomy (n=87) with minimisation for age, weight, gestational age at birth, bicarbonate at initial presentation, feeding type, preoperative duration of symptoms, and trial centre. Infants with a diagnosis of pyloric stenosis were eligible. Primary outcomes were time to achieve full enteral feed and duration of postoperative recovery. We aimed to recruit 200 infants (100 per group); however, the data monitoring and ethics committee recommended halting the trial before full recruitment because of significant treatment benefit in one group at interim analysis. Participants, parents, and nursing staff were unaware of treatment. Data were analysed on an intention-to-treat basis with regression analysis. The trial is registered with ClinicalTrials.gov, number NCT00144924. FINDINGS Time to achieve full enteral feeding in the open pyloromyotomy group was (median [IQR]) 23.9 h (16.0-41.0) versus 18.5 h (12.3-24.0; p=0.002) in the laparoscopic group; postoperative length of stay was 43.8 h (25.3-55.6) versus 33.6 h (22.9-48.1; p=0.027). Postoperative vomiting, and intra-operative and postoperative complications were similar between the two groups. INTERPRETATION Both open and laparoscopic pyloromyotomy are safe procedures for the management of pyloric stenosis. However, laparoscopy has advantages over open pyloromyotomy, and we recommend its use in centres with suitable laparoscopic experience.

Reflecting tidal wave beams and local generation of solitary waves in the ocean thermocline

It is generally accepted that ocean internal solitary waves can arise from the interaction of the barotropic tide with the continental shelf, which generates an internal tide that in turn steepens and forms solitary waves as it propagates shorewards. Some field observations, however, reveal large-amplitude internal solitary waves in deep water, hundreds of kilometres away from the continental shelf, suggesting an alternative generation mechanism: tidal flow over steep topography forces a propagating beam of internal tidal wave energy which impacts the thermocline at a considerable distance from the forcing site and gives rise to internal solitary waves there. Motivated by this possibility, a simple nonlinear long-wave model is proposed for the interaction of a tidal wave beam with the thermocline and the ensuing local generation of solitary waves. The thermocline is modelled as a density jump across the interface of a shallow homogeneous fluid layer on top of a deep uniformly stratified fluid, and a finite-amplitude propagating internal wave beam of tidal frequency in the lower fluid is assumed to be incident and reflected at the interface. The induced weakly nonlinear long-wave disturbance on the interface is governed in the far field by an integral-differential equation which accounts for nonlinear and dispersive effects as well as energy loss owing to radiation into the lower fluid. Depending on the strength of the thermocline and the intensity of the incident beam, nonlinear wave steepening can overcome radiation damping so a series of solitary waves may arise in the thermocline. Sample numerical solutions of the governing evolution equation suggest that this mechanism is quite robust for typical oceanic conditions.

On the generation of solitons and breathers in the modified Korteweg–de Vries equation

We consider the evolution of an initial disturbance described by the modified Korteweg-de Vries equation with a positive coefficient of the cubic nonlinear term, so that it can support solitons. Our primary aim is to determine the circumstances which can lead to the formation of solitons and/or breathers. We use the associated scattering problem and determine the discrete spectrum, where real eigenvalues describe solitons and complex eigenvalues describe breathers. For analytical convenience we consider various piecewise-constant initial conditions. We show how complex eigenvalues may be generated by bifurcation from either the real axis, or the imaginary axis; in the former case the bifurcation occurs as the unfolding of a double real eigenvalue. A bifurcation from the real axis describes the transition of a soliton pair with opposite polarities into a breather, while the bifurcation from the imaginary axis describes the generation of a breather from the continuous spectrum. Within the class of initial conditions we consider, a disturbance of one polarity, either positive or negative, will only generate solitons, and the number of solitons depends on the total mass. On the other hand, an initial disturbance with both polarities and very small mass will favor the generation of breathers, and the number of breathers then depends on the total energy. Direct numerical simulations of the modified Korteweg-de Vries equation confirms the analytical results, and show in detail the formation of solitons, breathers, and quasistationary coupled soliton pairs. Being based on spectral theory, our analytical results apply to the entire hierarchy of evolution equations connected with the same eigenvalue problem. (c) 2000 American Institute of Physics.

Surgery in Children With Crohn Disease Refractory to Medical Therapy

Objective: The aim of this study was to evaluate the results of surgery in children with Crohn disease (CD) not responding to medical therapy and establish whether surgery improves growth and nutrition. Patients and Methods: Children with CD diagnosed between 1998 and 2008 were reviewed. Relapse was defined by Harvey-Bradshaw index >5. Data, reported as median (range), were compared by Fisher exact test and repeated-measures ANOVA. Results: One hundred forty-one children, ages 12.7 years (3.5–16.8), were identified; 27 (19%) required surgery 14.5 months (1.1–61.8) after diagnosis. Twenty-one had elective surgery (19 isolated ileocaecal disease and stricture, 2 diffuse disease of ileum); 6 had emergency surgery (3 peritonitis, 2 haemorrhage, 1 perforation). Surgery included 18 ileocaecal resection and end-to-end anastomosis, 5 stoma formation, 2 left hemicolectomy and end-to-end anastomosis, and 2 stricturoplasty. Follow-up was 2.5 years (1–9.4). Growth and nutrition improved by 6 and 12 months after surgery, with a significant increase in weight z score (P < 0.0001), height z score (P < 0.0001), albumin (30 [13–36] vs 39 [30–46] vs 40 [33–45], P < 0.0001), and haemoglobin [10 (6.8–13.2) vs 11.7 (8.2–13.7) vs 12.0 (9.3–14.7), P < 0.0001]. All patients of the received azathioprine (2–2.5 mg · kg−1 · day−1) after surgery. Fifteen patients (55%) relapsed with a modified Harvey-Bradshaw index of 8 (6–11) within 11.5 months (4.2–33.4). Of these, 5 patients (18%) relapsed within 1 year. Five patients (18%) had further surgery (2 anastomotic strictures, 2 diseased stoma, and 1 enterocutaneous fistula). Conclusions: Growth and nutrition following surgery for CD improve, but there is a high relapse rate. Despite this, the improved growth and nutrition before relapse may be beneficial during puberty and justify surgery in children not responding to medications.

Pediatric Inguinal Hernia and Hydrocele: An Evidence-Based Review in the Era of Minimal Access Surgery

Pediatric inguinal hernia and hydrocele share a common etiology as well as management. The era of minimal access surgery is challenging the conventional surgical management for pediatric inguinal hernia in particular. This review article aims to highlight the nature of diagnosis and treatment for both hernia and hydrocele and examines both the traditional and contemporary treatment strategies from an evidence-based perspective.

Resonantly generated internal waves in a contraction

The near-resonant flow of a stratified fluid through a localized contraction is considered in the long-wavelength weakly nonlinear limit to investigate the transient development of nonlinear internal waves and whether these might lead to local steady hydraulic flows. It is shown that under these circumstances the response of the fluid will fall into one of three categories, the first governed by a forced Korteweg–de Vries equation and the latter two by a variable-coefficient form of this equation. The variable-coefficient equation is discussed using analytical approximations and numerical solutions when the forcing is of the same (positive) and of opposite (negative) polarity to that of free solitary waves in the fluid. For positive and negative forcing, strong and weak resonant regimes will occur near the critical point. In these resonant regimes for positive forcing the flow becomes locally steady within the contraction, while for negative forcing it remains unsteady within the contraction. The boundaries of these resonant regimes are identified in the limits of long and short contractions, and for a number of common stratifications.

Weakly nonlinear internal wave fronts trapped in contractions

The propagation of weakly nonlinear, long internal wave fronts in a contraction is considered in the transcritical limit as a model for the establishment of virtual controls. It is argued that the appropriate equation to describe this process is a variable coefficient Korteweg-de Vries equation. The solutions of this equation are then considered for compressive and rarefaction fronts. Rarefaction fronts exhibit both normal and virtual control solutions. However, the interaction of compressive fronts with contractions is intrinsically unsteady. Here the dynamics take two forms, interactions with the bulk of the front and interactions with individual solitary waves separating off from a front trapped downstream of the contraction

Motion Analysis–Based Skills Training and Assessment in Pediatric Laparoscopy: Construct, Concurrent, and Content Validity for the eoSim Simulator

PURPOSE To validate the eoSim(®) (eoSurgical Ltd., Edinburgh, Scotland, United Kingdom) simulator for pediatric laparoscopy. MATERIALS AND METHODS Participants were stratified according to their pediatric laparoscopy expertise. Three tasks were tested on the Pediatric Laparoscopic Surgery (PLS) and adapted eoSim simulators. Skill assessment was undertaken using motion analysis software for eoSim tasks and an existing validated scoring system for PLS tasks. Content validity was determined using Likert scale graded feedback responses. Construct validity was evaluated by investigating the respective abilities of the eoSim and PLS assessment tools to differentiate levels of experience. Concurrent validity was investigated by assessing the relationship between PLS and eoSim task completion times. RESULTS In total, 28 participants (8 experts, 7 intermediates, and 13 novices) were recruited. Content validity results were comparable or more favorable for the eoSim. Construct validity for motion analysis parameters was established for instrument path length (objects transfer, P = .025; suturing, P = .012), speed (suturing, P = .034), acceleration (suturing, P = .048), and smoothness (suturing, P < .001). For all tasks, there were significant differences between level of experience groups for eoSim task completion times and PLS scores (P = .038 to < .001). Significant relationships were found between eoSim and PLS task completion times for the precision cutting and suturing tasks (ρ = 0.298 and ρ = 0.435, respectively). CONCLUSIONS This study demonstrates validity of the adapted eoSim simulator for training in pediatric laparoscopy. Future work should focus on implementing and evaluating the proficiency-based training curriculum that is proposed using construct validity-derived metrics.

Weakly dispersive hydraulic flows in a contraction: Parametric solutions and linear stability

We consider the propagation of stratified fluid through a contraction near resonance, for which the governing asymptotic equation is the forced Korteweg–de Vries equation. Steady solutions of this equation are sought that have constant but differing amplitudes upstream and downstream of the contraction, and for which leading-order dispersive effects are retained. A numerical algorithm is outlined to obtain such solutions, yielding a parametric relationship between the normalized velocity perturbation and the normalized width perturbation. Matrix methods are then used to investigate the linear stability of these solutions.

AN EXACTLY SOLVABLE MODEL FOR THE INTERACTION OF LINEAR WAVES WITH KORTEWEG-DE VRIES SOLITONS ∗

Under certain mode-matching conditions, small-amplitude waves can be trapped by coupling to solitons of nonlinear fields. We present a model for this phenomenon, consisting of a linear equation coupled to the Korteweg--de Vries (KdV) equation. The model has one parameter, a coupling constant