An investigation into augmentation and preprocessing for optimising X-ray classification in limited datasets: a case study on necrotising enterocolitis

Purpose

Obtaining large volumes of medical images, required for deep learning development, can be challenging in rare pathologies. Image augmentation and preprocessing offer viable solutions. This work explores the case of necrotising enterocolitis (NEC), a rare but life-threatening condition affecting premature neonates, with challenging radiological diagnosis. We investigate data augmentation and preprocessing techniques and propose two optimised pipelines for developing reliable computer-aided diagnosis models on a limited NEC dataset.

Methods

We present a NEC dataset of 1090 Abdominal X-rays (AXRs) from 364 patients and investigate the effect of geometric augmentations, colour scheme augmentations and their combination for NEC classification based on the ResNet-50 backbone. We introduce two pipelines based on colour contrast and edge enhancement, to increase the visibility of subtle, difficult-to-identify, critical NEC findings on AXRs and achieve robust accuracy in a challenging three-class NEC classification task.

Results

Our results show that geometric augmentations improve performance, with Translation achieving +6.2%, while Flipping and Occlusion decrease performance. Colour augmentations, like Equalisation, yield modest improvements. The proposed Pr-1 and Pr-2 pipelines enhance model accuracy by +2.4% and +1.7%, respectively. Combining Pr-1/Pr-2 with geometric augmentation, we achieve a maximum performance increase of 7.1%, achieving robust NEC classification.

Conclusion

Based on an extensive validation of preprocessing and augmentation techniques, our work showcases the previously unreported potential of image preprocessing in AXR classification tasks with limited datasets. Our findings can be extended to other medical tasks for designing reliable classifier models with limited X-ray datasets. Ultimately, we also provide a benchmark for automated NEC detection and classification from AXRs.

An investigation into augmentation and preprocessing for optimising X-ray classification in limited datasets: a case study on necrotising enterocolitis

PURPOSE

Obtaining large volumes of medical images, required for deep learning development, can be challenging in rare pathologies. Image augmentation and preprocessing offer viable solutions. This work explores the case of necrotising enterocolitis (NEC), a rare but life-threatening condition affecting premature neonates, with challenging radiological diagnosis. We investigate data augmentation and preprocessing techniques and propose two optimised pipelines for developing reliable computer-aided diagnosis models on a limited NEC dataset.

METHODS

We present a NEC dataset of 1090 Abdominal X-rays (AXRs) from 364 patients and investigate the effect of geometric augmentations, colour scheme augmentations and their combination for NEC classification based on the ResNet-50 backbone. We introduce two pipelines based on colour contrast and edge enhancement, to increase the visibility of subtle, difficult-to-identify, critical NEC findings on AXRs and achieve robust accuracy in a challenging three-class NEC classification task.

RESULTS

Our results show that geometric augmentations improve performance, with Translation achieving +6.2%, while Flipping and Occlusion decrease performance. Colour augmentations, like Equalisation, yield modest improvements. The proposed Pr-1 and Pr-2 pipelines enhance model accuracy by +2.4% and +1.7%, respectively. Combining Pr-1/Pr-2 with geometric augmentation, we achieve a maximum performance increase of 7.1%, achieving robust NEC classification.

CONCLUSION

Based on an extensive validation of preprocessing and augmentation techniques, our work showcases the previously unreported potential of image preprocessing in AXR classification tasks with limited datasets. Our findings can be extended to other medical tasks for designing reliable classifier models with limited X-ray datasets. Ultimately, we also provide a benchmark for automated NEC detection and classification from AXRs.

Transitional Care In Patients With Hirschsprung Disease: Those Left Behind

BACKGROUND

The long term effects of Hirschsprung disease are clinically variable. Improved understanding of challenges patients may face as adults can help inform transitional care management.

OBJECTIVE

To explore the outcomes and transitional care experiences in adult patients with Hirschsprung.

DESIGN

Cohort study.

SETTING

Single center.

PATIENTS

All patients treated for Hirschsprung 1977-2001 (aged >18 at time of survey July 2018-2019). Eligible patients were sent validated multi-domain surveys as well as qualitative questions regarding their transitional care.

MAIN OUTCOME MEASURES

Status of transitional care, bowel function and quality of life assessment. Qualitative analysis of transitional care experience.

RESULTS

Of 139 patients, 20 had received transition care (10 had at least 1 visit but had been discharged and 10 were receiving ongoing follow-up). These patients had inferior bowel function and quality of life scores at follow-up. Twenty-three (17%) patients had issues with soiling at time of discharge, 7 received transitional care. Of these, 9/23 (39%) had a normal bowel function score (≥17), 5/23 (22%) had a poor score (<12) and one patient had since had a stoma formation. Eighteen (13%) patients had active moderate-severe issues related to bowel function, only 5 had been transitioned, and just 2 remained under ongoing care. Importantly, when these patients were discharged from our pediatric center, at a median age of 14 (IQR 12-16) years, 10/17 had no perceptible bowel issues, suggesting a worsening of function after discharge.

LIMITATIONS

The retrospective design and reliance on clinical notes to gather information of discharge status as well as patient recall of events.

CONCLUSION

There remains a small but significant proportion of Hirschsprung patients for whom bowel function either remains or becomes a major burden. These results support a need to better stratify patients requiring transitional care, and ensure a clear route to care if their status changes after discharge. See Video Abstract.

Validation of the Clavien-Madadi Classification for Unexpected Events in Pediatric Surgery: A Collaborative ERNICA Project

BACKGROUND

The Clavien-Madadi classification is a novel instrument for the assessment and grading of unexpected events in pediatric surgery, based on the Clavien-Dindo classification. The system has been adjusted to better fit the pediatric population in a prospective single-center study. There is a need now to validate the Clavien-Madadi classification within an international expert network.

METHODS

A pediatric surgical working group created 19 case scenarios with unexpected events in a multi-staged process. Those were circulated within the European Reference Network of Inherited and Congenital Anomalies (ERNICA) and surgeons were instructed to rate the scenarios according to the Clavien-Madadi vs. Clavien-Dindo classification.

RESULTS

59 surgeons from 12 European countries completed the questionnaire. Based on ratings of the case scenarios, the Clavien-Madadi classification showed significantly superior agreement rates of the respondents (85.9% vs 76.2%; p < 0.05) and was less frequently considered inaccurate for rating the pediatric population compared to Clavien-Dindo (2.1% vs 11.1%; p = 0.05). Fleiss' kappa analysis showed slightly higher strength of agreement using the Clavien-Madadi classification (0.74 vs 0.69). Additionally, intraclass correlation coefficient was slightly higher for the Clavien-Madadi compared to the Clavien-Dindo classification (ICCjust 0.93 vs 0.89; ICCunjust 0.93 vs 0.89). More pediatric surgeons preferred the Clavien-Madadi classification for the case scenarios (43.0% vs 11.8%; p = 0.002) and advantages of the Clavien-Madadi were confirmed by 81.4% of the surgeons.

CONCLUSION

The Clavien-Madadi classification is an accurate and reliable instrument for the grading of unexpected events in pediatric surgery. We therefore recommend its application in clinical and academic pediatric surgical practice.

LEVEL OF EVIDENCE

III.

Thoracoscopic Stage Internal Traction Repair Reduces Time to Achieve Esophageal Continuity in Long Gap Esophageal Atresia

OBJECTIVE

 Management of long gap esophageal atresia (LGOA) is controversial. This study aims at comparing the management of LGOA between two high-volume centers.

METHODS

 We included patients with LGOA (type A and B) between 2008 and 2022. Demographics, surgical methods, and outcomes were collected and compared.

RESULTS

 The study population involved 28 patients in center A and 24 patients in center B. A surgical approach was thoracoscopic in center A, only for one patient was open for final procedure. In center B, 3 patients were treated only thoracoscopically, 2 converted to open, and 19 as open surgery. In center A primary esophageal anastomosis concerned 1 case, two-staged esophageal lengthening using external traction 1 patient, and 26 were treated with the multistaged internal traction technique. In 24 patients a full anastomosis was achieved: in 23 patients only the internal traction technique was used, while 1 patient required open Collis-Nissen procedure as final management. In center B primary anastomosis was performed in 7 patients, delayed esophageal anastomosis in 8 patients, esophageal lengthening using external traction in 1 case, and 9 infants required esophageal replacement with gastric tube. Analyzed postoperative complications included: early mortality, 2/28 due to accompanied malformations (center A) and 0/24 (center B); anastomotic leakage, 4/26 (center A) treated conservatively-all patients had a contrast study-and 0/24 (center B), 1 case of pleural effusion, but no routine contrast study; recurrent strictures, 13/26 (center A) and 7/15 (center B); and need for fundoplication, 5/26 (center A) and 2/15 (center B). Age at esophageal continuity was as a median of 31 days in center A and 110 days in center B. Median time between initial procedure and esophageal anastomosis was 11 days in center A and 92 days in center B.

CONCLUSION

 Thoracoscopic internal traction technique reduces time to achieve esophageal continuity and the need for esophageal substitution while maintaining a similar early complication rate.

Ultrasound as the first line investigation for midgut malrotation: a UK tertiary centre experience

AIM

To present the first 22-months experience of transitioning to an ultrasound-first pathway for suspected midgut malrotation.

MATERIALS AND METHODS

An "ultrasound-first" imaging pathway was initiated in October 2021. Twenty-two-months later, a search was undertaken of all <1-year-old patients with "bilious", "malrotation," or "volvulus" as the imaging indication. Reports and images from upper gastrointestinal fluoroscopy (UGI) and ultrasound were reviewed, and diagnoses and outcomes were documented.

RESULTS

The search yielded 101 eligible cases between October 2021 and July 2023. Of the patients, 63/101 (62%) had both ultrasound and UGI: 47/63 (75%) ultrasound first, 16/63 (25%) UGI first. Thirty-one per cent (31/101) had ultrasound only and 7/70 (10%) UGI only. The pathway diagnosed 7/8 (88%) infants with midgut malrotation with or without volvulus and one infant who had an inconclusive ultrasound examination with a suspected an internal hernia and who was found to have malrotation volvulus at surgery. Twenty-one infants who had confidently normal ultrasound examinations and who also had UGI all had a normal duodenojejunal flexure position. Ultrasound detected alternative pathology in eight children. Duodenal visualisation improved with time: 6/15 (40%) in the first 6 months to 23/34 (68%) after the first year.

CONCLUSION

The transition to ultrasound as the first diagnostic test for midgut malrotation can be done safely and effectively in a UK centre, which previously relied solely on UGI.

Short and Medium Term Outcomes of Open and Laparoscopic Assisted Oesophageal Replacement Procedures

AIM OF THE STUDY

We describe the short- and medium-term outcomes following open and laparoscopic assisted oesophageal replacement surgery in a single tertiary paediatric surgical centre.

METHODS

A retrospective review (institutional audit approval no. 3213) on patients who underwent open or laparoscopic-assisted oesophageal replacement (OAR vs. LAR) at our centre between 2002 and 2021 was completed. Data collected (demographics, early complications, stricture formation, need for oesophageal dilatations, and mortality) were analysed using GraphPad Prism v 9.50 and are presented as median (IQR).

RESULTS

71 children (37 male) had oesophageal replacement surgery at a median age of 2.3 years (IQR 4.7 years). 51 were LAR (6 conversions). Replacement conduit was stomach (n = 67), colon (n = 3), or jejunum (n = 1). Most gastric transpositions had a pyloroplasty (46/67) or pyloromyotomy (14/67). Most common pathology was oesophageal atresia (n = 50 including 2 failed transpositions), caustic injury (n = 19 including 3 due to button battery), stricture of unknown cause (n = 1), and megaoesophagus (n = 1). There were 2 (2.8 %) early postoperative deaths at 2 days (major vessel thrombosis), 1 month (systemic sepsis), and one death at 5 years in the community. The rate of postoperative complications were comparable across LAR and OAR including anastomotic leak, pleural effusions, or early strictures. More patients with caustic pathology needed dilatations (60 % vs 30 % in OA, p = 0.05).

CONCLUSIONS

Outcomes of open and laparoscopic-assisted oesophageal replacement procedures are comparable in the short and medium term. Anastomotic stricture is higher in those with caustic injury.

LEVEL OF EVIDENCE

IV.

Congenital diaphragmatic hernia subtypes: Comparing birth prevalence, occurrence by maternal age, and mortality in a national birth cohort

BACKGROUND

Population-based administrative data have rarely been used to compare the birth prevalence, risk factors for occurrence, and mortality of congenital diaphragmatic hernia (CDH) subtypes.

OBJECTIVES

We used a national birth cohort to identify CDH subtypes and compared their birth prevalence, relationship with maternal age after accounting for sociodemographic factors, and 1-year mortality rates.

METHODS

Linked hospital admission and death records were used to identify isolated and complex CDH cases (involving additional anomalies) among singleton livebirths in England between 2002 and 2018. The prevalence of each CDH subtype per 10,000 livebirths was estimated overall and by infant, birth and maternal characteristics. The relationship between maternal age and each subtype relative to no CDH was examined using multivariable log-binomial regression to estimate risk ratios (RRs). One-year mortality rates were examined using Kaplan-Meier curves and the hazard ratio (HR) of complex versus isolated CDH was calculated using Cox regression.

RESULTS

Among 9.5 million livebirths, we identified 1285 with isolated CDH and 1150 with complex CDH. The overall prevalence of isolated and complex CDH was 1.4 (95% confidence interval [CI] 1.3, 1.4) and 1.2 (95% CI 1.1, 1.3) per 10,000 livebirths, respectively. Only complex CDH was associated with maternal age. Compared with maternal age 25-34 years, complex CDH risk was elevated for maternal age < 20 years (RR 1.31, 95% CI 1.00, 1.72). Risk was highest for maternal age ≥ 40 years (RR 1.61, 95% CI 1.21, 2.15) although accounting for chromosomal anomalies attenuated the risk (RR 1.39, 95% CI 1.00, 1.92). The 1-year mortality rate for complex CDH (33.1%, 95% CI 30.5, 35.9) was slightly higher than for isolated CDH (29.7%, 95% CI 27.3, 32.3) (HR 1.10, 95% CI 0.96, 1.27).

CONCLUSIONS

Mechanisms of occurrence differed between and within CDH subtypes and 1-year mortality of complex CDH was slightly higher than for isolated CDH.

Thoracoscopic vs open repair of congenital diaphragmatic hernia after extracorporeal membrane oxygenation: a comparison of intra-operative data

PURPOSE

ECMO is an escalation treatment for hypoxic respiratory failure in patients with CDH. Open repair has been advocated after ECMO indicating that physiological changes associated to thoracoscopic repair were not well tolerated.

METHODS

We have performed a retrospective review of all patients who underwent ECMO prior CDH repair over a 7 year period (2015-2021). Outcome measures were intra-operative Ph, PCO2, PO2 and FiO2 at 30 min, 1 h 30 min, and 2 h 30 min of surgery, operative time and recurrence rate. Data are shown in median (range).

RESULTS

Eleven patients required ECMO prior CDH repair. Six of eleven (55%) were done thoracoscopically (Group A) and five of eleven (45%) via laparotomy (Group B). Two of six (33%) patients (Group A) were converted to a laparotomy, one of six (16%) patient developed a recurrence, and there was no recurrence in Group B. Two of five (40%) patients died within the first 60 days of life, whilst there was no death in Group A. Intra-operative values are shown below.

CONCLUSION

Whilst this is a preliminary report of a limited number of patients, there is no obvious difference of intra-operative blood gas parameters during surgical repair in patients after ECMO. Thoracoscopic CDH repair may be considered in patients after ECMO.

Regenerative medicine: prenatal approaches

This two-paper Series focuses on recent advances and applications of regenerative medicine that could benefit paediatric patients. Innovations in genomic, stem-cell, and tissue-based technologies have created progress in disease modelling and new therapies for congenital and incurable paediatric diseases. Prenatal approaches present unique opportunities associated with substantial biotechnical, medical, and ethical obstacles. Maternal plasma fetal DNA analysis is increasingly adopted as a noninvasive prenatal screening or diagnostic test for chromosomal and monogenic disorders. The molecular basis for cell-free DNA detection stimulated the development of circulating tumour DNA testing for adult cancers. In-utero stem-cell, gene, gene-modified cell (and to a lesser extent, tissue-based) therapies have shown early clinical promise in a wide range of paediatric disorders. Fetal cells for postnatal treatment and artificial placenta for ex-utero fetal therapies are new frontiers in this exciting field.

Fluorescence-Guided Surgery (FGS) during a Laparoscopic Redo Nissen Fundoplication: The First Case in Children

We present the first case of fluorescence-guided surgery (FGS) using indocyanine green (ICG) in a pediatric redo-Nissen fundoplication. The patient is a 17-year-old male with recurrent gastroesophageal symptoms who underwent primary antireflux surgery at 10 months of age. During the redo fundoplication, ICG was intravenously administered to help the visualization during the adhesiolysis between liver, stomach and right crus of the diaphragm and to spare small oesophageal vessels and the left gastric artery. In this case, FGS made the surgery easier than usual and likely reduced the risk of intra-operative complications. Therefore, we believe that this new technology should be regularly used in these types of complex intra-abdominal redo operations.

Maintaining a minimally invasive surgical service during a pandemic

PURPOSE

The safety of minimally invasive surgery (MIS) was questioned in the COVID-19 pandemic due to concern regarding disease spread. We continued MIS during the pandemic with appropriate protective measures. This study aims to assess the safety of MIS compared to Open Surgery (OS) in this setting.

METHODS

Operations performed during 2020 lockdown were compared with operations from the same time-period in 2019 and 2021. Outcomes reviewed included all complications, respiratory complications, length of stay (LOS) and operating surgeon COVID-19 infections (OSI).

RESULTS

In 2020, MIS comprised 52% of procedures. 29% of MIS 2020 had complications (2019: 24%, 2021: 15%; p = 0.08) vs 47% in OS 2020 (p = 0.04 vs MIS). 8.5% of MIS 2020 had respiratory complications (2019: 7.7%, 2021: 6.9%; p = 0.9) vs 10.5% in OS 2020 (p = 0.8 vs MIS). Median LOS[IQR] for MIS 2020 was 2.5[6] days vs 5[23] days in OS 2020 (p = 0.06). In 2020, 2 patients (1.2%) were COVID-19 positive (MIS: 1, OS: 1) and there were no OSI.

CONCLUSION

Despite extensive use of MIS during the pandemic, there was no associated increase in respiratory or other complications, and no OSI. Our study suggests that, with appropriate protective measures, MIS can be performed safely despite high levels of COVID-19 in the population.

Indocyanine Green-Based Fluorescence-Guided Surgery in a Male Infant with Anorectal Malformation

Reconstructive techniques for complex anorectal malformations (ARMs) require intestinal pull-through on vascular pedicles. Traditionally, the visual inspection of the intestinal perfusion is the sole modality adopted to assess tissue viability. In this article, we report the case of a child with a rectourethral prostatic fistula, who had a Peña's descending colostomy with distal mucous fistula in the neonatal period and a posterior sagittal anorectoplasty at 6 months of life. The ARM repair was guided by indocyanine green (ICG), which was intravenously administered to evaluate the blood flow of the intestinal pull-through using the EleVision IR system (Medtronic Ltd, U.K.). ICG-based fluorescence-guided surgery helped to define the proximal resection margin, impacting intraoperative decision making, and no postoperative complications occurred. We envisage that this technology will become part of the armory of pediatric surgeons soon, by reducing the risk of intra- and postoperative complications.

Postnatal outcome of prenatally-detected "simple" renal cysts: Are they really simple?

BACKGROUND

The majority of simple renal cysts diagnosed postnatally are asymptomatic and rarely require treatment unless they become symptomatic or complex. We hypothesised that prenatally-detected simple renal cysts would have a similar harmless outcome.

AIMS

To establish the natural history and postnatal outcome of prenatally-diagnosed simple renal cysts.

STUDY DESIGN

Single-centre retrospective case-series review (12-year period).

SUBJECTS

All patients with prenatally-diagnosed simple renal cysts (defined as a solitary, non-septated, non-communicating cyst in an otherwise normal kidney).

OUTCOME MEASURES

Prenatal and postnatal changes to cyst size, persistence, resolution or modification of diagnosis. Data is presented as the proportion of patients or median (range).

RESULTS

30 cysts were detected (2 bilateral, 26 unilateral) in 28 fetuses (median gestational age of 23 [20-36] weeks). Median maximum diameter was 15 (4-35) mm at initial diagnosis and 17.5 (4-100) mm across all prenatal scans. On follow-up scans diagnosis was modified in 16 (53%) to: multicystic dysplastic kidney (MCDK), dilated duplex kidney, hydronephrosis, urinoma, renal agenesis and adrenal mass. 12 (40%) cysts resolved. 2 (7%) asymptomatic cysts persisted at one year postnatally. Cyst maximum diameter in the modified diagnosis group (21.5 [10-100] mm) was significantly larger than the simple cyst group (12 [4-20] mm) (P = 0.03).

CONCLUSIONS

Our study revealed the challenges of prenatal ultrasound imaging, with modified diagnoses in over half the cases. Kidneys with solitary cysts could evolve into multicystic kidneys or involute completely, which suggests a true alteration in morphology rather than sonographic error. Persistent simple cysts in an otherwise normal kidney, however, resolved spontaneously or remained asymptomatic. Prenatally-detected simple cysts should be monitored with serial imaging.

Early remote ischaemic preconditioning leads to sustained improvement in allograft function after live donor kidney transplantation: long-term outcomes in the REnal Protection Against Ischaemia-Reperfusion in transplantation (REPAIR) randomised trial

BACKGROUND

The REnal Protection Against Ischaemia-Reperfusion in transplantation (REPAIR) RCT examined whether remote ischaemic preconditioning (RIPC) improved renal function after living-donor kidney transplantation. The primary endpoint, glomerular filtration rate (GFR), quantified by iohexol at 12 months, suggested that RIPC may confer longer-term benefit. Here, we present yearly follow-up data of estimated GFR for up to 5 yr after transplantation.

METHODS

In this double-blind, factorial RCT, we enrolled 406 adult live donor kidney transplant donor-recipient pairs in 15 European transplant centres. RIPC was performed before induction of anaesthesia. RIPC consisted of four 5 min inflations of a BP cuff on the upper arm to 40 mm Hg above systolic BP separated by 5 min periods of cuff deflation. For sham RIPC, cuff inflation to 40 mm Hg was undertaken. Pairs were randomised to sham RIPC, early RIPC only (immediately pre-surgery), late RIPC only (24 h pre-surgery), or dual RIPC (early and late RIPC). The pre-specified secondary outcome of estimated GFR (eGFR) was calculated from serum creatinine measurements, using the Chronic Kidney Disease Epidemiology Collaboration equation. Predefined safety outcomes were mortality and graft loss.

RESULTS

There was a sustained improvement in eGFR after early RIPC, compared with control from 3 months to 5 yr (adjusted mean difference: 4.71 ml min^-1 (1.73 m)^-2 [95% confidence interval, CI: 1.54-7.89]; P=0.004). Mortality and graft loss were similar between groups (RIPC: 20/205 [9.8%] vs control 24/201 [11.9%]; hazard ratio: 0.79 [95% CI: 0.43-1.43]).

CONCLUSIONS

RIPC safely improves long-term kidney function after living-donor renal transplantation when administered before induction of anaesthesia.

CLINICAL TRIAL REGISTRATION

ISRCTN30083294.

Fetal abdominal cysts: antenatal course and postnatal outcomes

Background There is little information on which to base the prognostic counselling as to whether an antenatally diagnosed fetal abdominal cyst will grow or shrink, or need surgery. This study aims to provide contemporary data on prenatally diagnosed fetal abdominal cysts in relation to their course and postnatal outcomes. Methods Fetal abdominal cysts diagnosed over 11 years in a single centre were identified. The gestational age at diagnosis and cyst characteristics at each examination were recorded (size, location, echogenity, septation and vascularity) and follow-up data from postnatal visits were collected. Results Eighty abdominal cysts were identified antenatally at 28+4 weeks (range 11+0-38+3). Most (87%) were isolated and the majority were pelvic (52%), simple (87.5%) and avascular (100%). Antenatally, 29% resolved spontaneously; 29% reduced in size; 9% were stable and 33% increased in size. Forty-one percent of cysts under 20 mm diameter increased in size, while only 20% of cysts with a diameter of over 40 mm increased in size. The majority of cysts were ovarian in origin (n=45, 56%), followed by intestinal (n=15, 18%), choledochal (n=3, 4%), liver (n=2, 3%) and renal/adrenal origins (n=2, 3%), respectively. In 16% (n=13), the antenatal diagnosis was not obvious. Seventy-five percent of the cysts that persisted postnatally required surgical intervention. Conclusion Most antenatally diagnosed fetal abdominal cysts were ovarian in origin. Though most disappeared antenatally, nearly three quarters required surgical intervention when present after birth. Cysts of intestinal origin are more difficult to diagnose antenatally and often require surgery.

In utero therapy for congenital disorders using amniotic fluid stem cells

Congenital diseases are responsible for over a third of all pediatric hospital admissions. Advances in prenatal screening and molecular diagnosis have allowed the detection of many life-threatening genetic diseases early in gestation. In utero transplantation (IUT) with stem cells could cure affected fetuses but so far in humans, successful IUT using allogeneic hematopoietic stem cells (HSCs), has been limited to fetuses with severe immunologic defects and more recently IUT with allogeneic mesenchymal stem cell transplantation, has improved phenotype in osteogenesis imperfecta. The options of preemptive treatment of congenital diseases in utero by stem cell or gene therapy changes the perspective of congenital diseases since it may avoid the need for postnatal treatment and reduce future costs. Amniotic fluid stem (AFS) cells have been isolated and characterized in human, mice, rodents, rabbit, and sheep and are a potential source of cells for therapeutic applications in disorders for treatment prenatally or postnatally. Gene transfer to the cells with long-term transgenic protein expression is feasible. Recently, pre-clinical autologous transplantation of transduced cells has been achieved in fetal sheep using minimally invasive ultrasound guided injection techniques. Clinically relevant levels of transgenic protein were expressed in the blood of transplanted lambs for at least 6 months. The cells have also demonstrated the potential of repair in a range of pre-clinical disease models such as neurological disorders, tracheal repair, bladder injury, and diaphragmatic hernia repair in neonates or adults. These results have been encouraging, and bring personalized tissue engineering for prenatal treatment of genetic disorders closer to the clinic.

Remote ischemic preconditioning protects the brain against injury after hypothermic circulatory arrest

BACKGROUND

Ischemic preconditioning (IPC) is a mechanism protecting tissues from injury during ischemia and reperfusion. Remote IPC (RIPC) can be elicited by applying brief periods of ischemia to tissues with ischemic tolerance, thus protecting vital organs more susceptible to ischemic damage. Using a porcine model, we determined whether RIPC of the limb is protective against brain injury caused by hypothermic circulatory arrest (HCA).

METHODS AND RESULTS

Twelve piglets were randomized to control and RIPC groups. RIPC was induced in advance of cardiopulmonary bypass by 4 cycles of 5 minutes of ischemia of the hind limb. All animals underwent cardiopulmonary bypass followed by 60 minutes of HCA at 18°C. Brain metabolism and electroencephalographic activity were monitored for 8 hours after HCA. Assessment of neurological status was performed for a week postoperatively. Finally, brain tissue was harvested for histopathological analysis. Study groups were balanced for baseline and intraoperative parameters. Brain lactate concentration was significantly lower (P<0.0001, ANOVA) and recovery of electroencephalographic activity faster (P<0.05, ANOVA) in the RIPC group. RIPC had a beneficial effect on neurological function during the 7-day follow-up (behavioral score; P<0.0001 versus control, ANOVA). Histopathological analysis demonstrated a significant reduction in cerebral injury in RIPC animals (injury score; mean [interquartile range]: control 5.8 [3.8 to 7.5] versus RIPC 1.5 [0.5 to 2.5], P<0.001, t test).

CONCLUSIONS

These data demonstrate that RIPC protects the brain against HCA-induced injury, resulting in accelerated recovery of neurological function. RIPC might be neuroprotective in patients undergoing surgery with HCA and improve long-term outcomes. Clinical trials to test this hypothesis are warranted.

Inorganic nitrate supplementation lowers blood pressure in humans: role for nitrite-derived NO

Ingestion of dietary (inorganic) nitrate elevates circulating and tissue levels of nitrite via bioconversion in the entero-salivary circulation. In addition, nitrite is a potent vasodilator in humans, an effect thought to underlie the blood pressure-lowering effects of dietary nitrate (in the form of beetroot juice) ingestion. Whether inorganic nitrate underlies these effects and whether the effects of either naturally occurring dietary nitrate or inorganic nitrate supplementation are dose dependent remain uncertain. Using a randomized crossover study design, we show that nitrate supplementation (KNO(3) capsules: 4 versus 12 mmol [n=6] or 24 mmol of KNO(3) (1488 mg of nitrate) versus 24 mmol of KCl [n=20]) or vegetable intake (250 mL of beetroot juice [5.5 mmol nitrate] versus 250 mL of water [n=9]) causes dose-dependent elevation in plasma nitrite concentration and elevation of cGMP concentration with a consequent decrease in blood pressure in healthy volunteers. In addition, post hoc analysis demonstrates a sex difference in sensitivity to nitrate supplementation dependent on resting baseline blood pressure and plasma nitrite concentration, whereby blood pressure is decreased in male volunteers, with higher baseline blood pressure and lower plasma nitrite concentration but not in female volunteers. Our findings demonstrate dose-dependent decreases in blood pressure and vasoprotection after inorganic nitrate ingestion in the form of either supplementation or by dietary elevation. In addition, our post hoc analyses intimate sex differences in nitrate processing involving the entero-salivary circulation that are likely to be major contributing factors to the lower blood pressures and the vasoprotective phenotype of premenopausal women.

Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitrite

Diets rich in fruits and vegetables reduce blood pressure (BP) and the risk of adverse cardiovascular events. However, the mechanisms of this effect have not been elucidated. Certain vegetables possess a high nitrate content, and we hypothesized that this might represent a source of vasoprotective nitric oxide via bioactivation. In healthy volunteers, approximately 3 hours after ingestion of a dietary nitrate load (beetroot juice 500 mL), BP was substantially reduced (Delta(max) -10.4/8 mm Hg); an effect that correlated with peak increases in plasma nitrite concentration. The dietary nitrate load also prevented endothelial dysfunction induced by an acute ischemic insult in the human forearm and significantly attenuated ex vivo platelet aggregation in response to collagen and ADP. Interruption of the enterosalivary conversion of nitrate to nitrite (facilitated by bacterial anaerobes situated on the surface of the tongue) prevented the rise in plasma nitrite, blocked the decrease in BP, and abolished the inhibitory effects on platelet aggregation, confirming that these vasoprotective effects were attributable to the activity of nitrite converted from the ingested nitrate. These findings suggest that dietary nitrate underlies the beneficial effects of a vegetable-rich diet and highlights the potential of a "natural" low cost approach for the treatment of cardiovascular disease.

Human pulmonary valve progenitor cells exhibit endothelial/mesenchymal plasticity in response to vascular endothelial growth factor-A and transforming growth factor-beta2

In situ analysis of fetal semilunar valve leaflets has revealed cells coexpressing endothelial and mesenchymal markers along the endothelium, with diminished frequency seen in adult valves. To determine whether such cells are progenitor cells, we isolated clonal populations from human pulmonary valves. The clones expressed endothelial markers but showed potential to further differentiate into endothelium in response to vascular endothelial growth factor (VEGF)-A. When exposed to transforming growth factor (TGF)-beta2, individual clones adopted a mesenchymal phenotype to varying degrees and expressed markers of endothelial to mesenchymal transformation (EMT). Both VEGF- and TGFbeta2-induced phenotypic changes were partially reversible, indicating the plasticity of these cells. When challenged with VEGF or TGFbeta2, a hierarchy of endothelial/mesenchymal potential could be seen among the clonal populations: cells initially closer to an endothelial phenotype showed a strong response to TGFbeta2 that could be inhibited by VEGF, whereas cells closer to a mesenchymal phenotype responded to TGFbeta2 but were resistant to endothelial-inducing effects of VEGF. These findings suggest the presence of bipotential valve progenitor cells with ability to differentiate into either endothelial or interstitial cells of the valve leaflet. Understanding the differentiation potential and function of these cells may be important for understanding heart valve disease and may also be applied to current paradigms for creating tissue-engineered heart valves.

Effect of inhibitors of the renin-angiotensin system and other antihypertensive drugs on renal outcomes: systematic review and meta-analysis

BACKGROUND

A consensus has emerged that angiotensin-converting-enzyme (ACE) inhibitors and angiotensin-II receptor blockers (ARBs) have specific renoprotective effects. Guidelines specify that these are the drugs of choice for the treatment of hypertension in patients with renal disease. We sought to determine to what extent this consensus is supported by the available evidence.

METHODS

Electronic databases were searched up to January, 2005, for randomised trials assessing antihypertensive drugs and progression of renal disease. Effects on primary discrete endpoints (doubling of creatinine and end-stage renal disease) and secondary continuous markers of renal outcomes (creatinine, albuminuria, and glomerular filtration rate) were calculated with random-effect models. The effects of ACE inhibitors or ARBs in placebo-controlled trials were compared with the effects seen in trials that used an active comparator drug.

FINDINGS

Comparisons of ACE inhibitors or ARBs with other antihypertensive drugs yielded a relative risk of 0.71 (95% CI 0.49-1.04) for doubling of creatinine and a small benefit on end-stage renal disease (relative risk 0.87, 0.75-0.99). Analyses of the results by study size showed a smaller benefit in large studies. In patients with diabetic nephropathy, no benefit was seen in comparative trials of ACE inhibitors or ARBs on the doubling of creatinine (1.09, 0.55-2.15), end-stage renal disease (0.89, 0.74-1.07), glomerular filtration rate, or creatinine amounts. Placebo-controlled trials of ACE inhibitors or ARBs showed greater benefits than comparative trials on all renal outcomes, but were accompanied by substantial reductions in blood pressure in favour of ACE inhibitors or ARBs.

INTERPRETATION

The benefits of ACE inhibitors or ARBs on renal outcomes in placebo-controlled trials probably result from a blood-pressure-lowering effect. In patients with diabetes, additional renoprotective actions of these substances beyond lowering blood pressure remain unproven, and there is uncertainty about the greater renoprotection seen in non-diabetic renal disease.

Validation of a device to measure arterial pulse wave velocity by a photoplethysmographic method

We aimed to validate a new method for measuring arterial pulsewave transit time and pulsewave velocity (a measure of arterial elasticity), based on the principle of photoplethysmography (PPG), and to compare transcutaneous values with those obtained by intra-arterial measurements. Three validation experiments are described. (a) PPG pulse wave delay times (defined as the time interval between the ECG R wave and the foot of the arterial pulse wave measured at the wrist or ankle) were compared to values obtained simultaneously from an established methodology (Doppler ultrasound). (b) Aortic pulsewave delay times in 17 subjects obtained non-invasively by the PPG method were compared with those obtained from the intra-arterial pressure wave. (c) Repeatability measurements of PWV on the same subjects were carried out over two timescales (minutes and hours) in the arm, the leg and the trunk. The Doppler and PPG delay times correlated well, as did intra-arterial and transcutaneous values. Repeatability at short timescales was good (coefficients of variation (CV) < 6% for all measurement sites) and, at the longer timescale, was satisfactory (CVs in the aorta, the arm and leg were 6.3, 13.1 and 16.0, respectively). The PWV values agreed well with others in the literature. We conclude that the PPG technique provides a complement to existing methods for the non-invasive measurement of arterial compliance. Its simplicity and ease of use make it suitable for large-scale epidemiological studies.