Is preoperative gastroscopy necessary before sleeve gastrectomy and Roux-en-Y gastric bypass?

Background: Consensus on the necessity of esophagogastroduodenoscopy (EGD) before bariatric surgery is lacking. Recommendations and practices vary by country and unit. Several reports have expressed concerns on gastroesophageal reflux disease (GERD) and its consequences after sleeve gastrectomy (SG) and the risk of leaving a premalignant lesion in the excluded stomach after Roux en -Y gastric bypass (RYGB). Objectives: We explored the number and types of clinically significant findings in preoperative EGDs and how they associate with preexisting GERD-symptoms (SG) and premalignant lesions (RYGB). We also studied how many reoperations were performed due to postoperative GERD in SG-patients. Setting: University hospital. Methods: We investigated preoperative EGD-findings and gastrointestinal symptoms before bariatric surgery in all patients with a primary bariatric operation in our unit between December 2007 and May 2016. Results: We performed 1474 operations: 1047 (71.0%) RYGB, 407 (27.6%) SG, and 20 (1.4%) others. One thousand two hundred seventy-five (86.5%) preoperative EGD reports were analyzed: 647 (50.7%) EGDs were completely normal. Altogether, 294 patients (23.0% of total) had a clinically significant finding that was relevant for SG (hiatal hernia, esophagitis, Barrett's esophagus, esophageal dysplasia), 144 (49.0%) of whom reported gastrointestinal symptoms. Twenty patients (1.6%) had a significant finding relevant for RYGB (peptic ulcer, atrophic gastritis, gastrointestinal stromal tumor), and 6 (30%) reported gastrointestinal symptoms. Thirteen (3.2%) SGs were converted into RYGB due to GERD. Conclusions: Preoperative EGD is indicated before SG but not before RYGB for asymptomatic patients without a risk for gastric pathology. (C) American Society for Metabolic and Bariatric Surgery. All rights reserved.Peer reviewe

Vacancy-Impurity Complexes in Highly Sb-Doped Si Grown by Molecular Beam Epitaxy

Positron annihilation measurements, supported by first-principles electron-structure calculations, identify vacancies and vacancy clusters decorated by 1–2 dopant impurities in highly Sb-doped Si. The concentration of vacancy defects increases with Sb doping and contributes significantly to the electrical compensation. Annealings at low temperatures of 400–500 K convert the defects to larger complexes where the open volume is neighbored by 2–3 Sb atoms. This behavior is attributed to the migration of vacancy-Sb pairs and demonstrates at atomic level the metastability of the material grown by epitaxy at low temperature.Peer reviewe

Identification of Vacancy-Impurity Complexes in Highly n-Type Si

We show that the detailed atomic structure of vacancy-impurity complexes in Si can be experimentally determined by combining positron lifetime and electron momentum distribution measurements. The vacancies complexed with a single impurity, V−P and V−As, are identified in electron irradiated Si. The formation of native vacancy defects is observed in highly As-doped Si at the doping level of 1020cm−3. The defects are identified as monovacancies surrounded by three As atoms. The formation of a V−As3 complex is consistent with the theoretical descriptions of As diffusion and electrical deactivation in highly As-doped Si.Peer reviewe

Identification of vacancy defects in compound semiconductors by core-electron annihilation: Application to InP

We show that the Doppler broadening of positron annihilation radiation can be used in the identification of vacancy defects in compound semiconductors. Annihilation of trapped positrons with surrounding core electrons reveals chemical information that becomes visible when the experimental backgorund is reduced by the coincidence technique. We also present a simple calculational scheme to predict the high-momentum part of the annihilation line. The utility of the method is demonstrated by providing results for vacancies in InP. In electron irradiated InP the isolated In and P vacancies are distinguished from each other by the magnitude of the core-electron annihilation. In heavily Zn-doped InP we detect a native vacancy defect and identify it to a P vacancy decorated by Zn atoms.Peer reviewe

Bile Reflux is a Common Finding in the Gastric Pouch After One Anastomosis Gastric Bypass

INTRODUCTION: Data on postoperative bile reflux after one anastomosis gastric bypass (OAGB) is lacking. Bile reflux scintigraphy (BRS) has been shown to be a reliable non-invasive tool to assess bile reflux after OAGB. We set out to study bile reflux after OAGB with BRS and endoscopy in a prospective series (RYSA Trial). METHODS: Forty patients (29 women) underwent OAGB between November 2016 and December 2018. Symptoms were reported and upper gastrointestinal endoscopy (UGE) was done preoperatively. Six months after OAGB, bile reflux was assessed in UGE findings and as tracer activity found in gastric tube and esophagus in BRS (follow-up rate 95%). RESULTS: Twenty-six patients (68.4%) had no bile reflux in BRS. Twelve patients (31.6%) had bile reflux in the gastric pouch in BRS and one of them (2.6%) had bile reflux also in the esophagus 6 months postoperatively. Mean bile reflux activity in the gastric pouch was 5.2% (1-21%) of total activity. De novo findings suggestive of bile reflux (esophagitis, stomal ulcer, foveolar inflammation of gastric pouch) were found for 15 patients (39.5%) in postoperative UGE. BRS and UGE findings were significantly associated (P = 0.022). Eight patients experienced de novo reflux symptoms at 6 months, that were significantly associated with BRS and de novo UGE findings postoperatively (P = 0.033 and 0.0005, respectively). CONCLUSION: Postoperative bile reflux in the gastric pouch after OAGB is a common finding in scintigraphy and endoscopy. The long-term effects of bile exposure will be analyzed in future reports after a longer follow-up. TRIAL REGISTRATION: Clinical Trials Identifier NCT02882685.Peer reviewe

Clustering of vacancy defects in high-purity semi-insulating SiC

Positron lifetime spectroscopy was used to study native vacancy defects in semi-insulating silicon carbide. The material is shown to contain (i) vacancy clusters consisting of 4--5 missing atoms and (ii) Si vacancy related negatively charged defects. The total open volume bound to the clusters anticorrelates with the electrical resistivity both in as-grown and annealed material. Our results suggest that Si vacancy related complexes compensate electrically the as-grown material, but migrate to increase the size of the clusters during annealing, leading to loss of resistivity.Comment: 8 pages, 5 figure