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Lymphocytic oesophagitis is a rare inflammatory condition that was first described in 2006. Although it is being increasingly diagnosed, it remains poorly described and characterised. There is limited research on the natural history, diagnosis and management of this condition. The most common presenting symptoms are dysphagia, chest pain and heartburn. Endoscopic features can mimic eosinophilic oesophagitis. International consensus is needed to secure a histological definition, to agree on an endoscopic severity scoring system and to determine an appropriate management algorithm. This review summarises the main evidence for the diagnosis and management of lymphocytic oesophagitis, thus setting the scene for the future directions needed to improve the management of this condition., (© Royal College of Physicians 2023. All rights reserved.)

Achalasia is a major esophageal motor disorder featured by the altered relaxation of the esophagogastric junction in the absence of effective peristaltic activity. As a consequence of the esophageal outflow obstruction, achalasia patients present with clinical symptoms of dysphagia, chest pain, weight loss, and regurgitation of indigested food. Other less specific symptoms can also present including heartburn, chronic cough, and aspiration pneumonia. The delay in diagnosis, particularly when the presenting symptoms mimic those of gastroesophageal reflux disease, may be as long as several years. The widespread use of high-resolution manometry has permitted earlier detection and uncovered achalasia phenotypes which can have prognostic and therapeutic implications. Other tools have also emerged to help define achalasia severity and which can be used as objective measures of response to therapy including the timed barium esophagogram and the functional lumen imaging probe. Such diagnostic innovations, along with the increased awareness by clinicians and patients due to the availability of alternative therapeutic approaches (laparoscopic and robotic Heller myotomy, and peroral endoscopic myotomy) have radically changed the natural history of the disorder. Herein, we report the most recent advances in the diagnosis, classification, and management of esophageal achalasia and underline the still-grey areas that needs to be addressed by future research to reach the goal of personalizing treatment.

Despite its higher prevalence among men, women with thoracic aortic aneurysm and dissection (TAAD) have lower rates of treatment and surgical intervention and often have worse outcomes. A growing number of women with TAAD also desire pregnancy, which can be associated with an increased risk of aortic complications. Understanding sex-specific differences in TAAD has the potential to improve care delivery, reduce disparities in treatment, and optimize outcomes for women with TAAD., Competing Interests: Funding Support and Author Disclosures The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

The prevalence of the gastro-oesophageal reflux disease (GORD) in the western world is increasing. Uncontrolled GORD can lead to harmful long-term sequela such as oesophagitis, stricture formation, Barrett's oesophagus and oesophageal adenocarcinoma. Moreover, GORD has been shown to negatively impact quality of life. The current treatment paradigm for GORD consists of lifestyle modification, pharmacological control of gastric acid secretion or antireflux surgery. In recent years, several minimally invasive antireflux endoscopic therapies (ARET) have been developed which may play a role in bridging the unmet therapeutic gap between the medical and surgical treatment options. To ensure optimal patient outcomes following ARET, considered patient selection is crucial, which requires a mechanistic understanding of individual ARET options. Here, we will discuss the differences between ARETs along with an overview of the current evidence base. We also outline future research priorities that will help refine the future role of ARET., Competing Interests: Competing interests: RH receives educational grants to support research infrastructure from Medtronic. Cook endoscopy (fellowship support), Pentax Europe, C2 therapeutics, Beamline diagnostic and Fractyl. VS receives honorarium for professional services from Pentax Europe, Medtronic, Astra Zeneca and Pharmacosmos. RS receives honoraria for running course and speaking at symposia for Medtronic, Johnson & Johnson, Falk Pharma, Medispar. HE is also on the advisory board for Johnson and Johnson and Falk Pharma., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background Cigarette smoking is significantly associated with premature death related and not related to cardiovascular disease (CVD). Whether risk associated with smoking is similar across CVD subtypes and how this translates into years of life lost is not known. Methods and Results We pooled and harmonized individual-level data from 9 population-based cohorts in the United States. All participants were free of clinical CVD at baseline with available data on current smoking status, covariates, and CVD outcomes. We examined the association between smoking status and total CVD and CVD subtypes, including fatal and nonfatal coronary heart disease, stroke, congestive heart failure, and other CVD deaths. We performed (1) modified Kaplan-Meier analysis to estimate long-term risks, (2) adjusted competing Cox models to estimate joint cumulative risks for CVD or noncardiovascular death, and (3) Irwin's restricted mean to estimate years lived free from and with CVD. Of 106 165 adults, 50.4% were women. Overall long-term risks for CVD events were 46.0% (95% CI, 44.7-47.3) and 34.7% (95% CI, 33.3-36.0) in middle-aged men and women, respectively. In middle-aged men who reported smoking compared with those who did not smoke, competing hazard ratios (HRs) were higher for the first presentation being a fatal CVD event (HR, 1.79 [95% CI, 1.68-1.92]), with a similar pattern among women (HR,1.82 [95% CI, 1.68-1.98]). Smoking was associated with earlier CVD onset by 5.1 and 3.8 years in men and women. Similar patterns were observed in younger and older adults. Conclusions Current smoking was associated with a fatal event as the first manifestation of clinical CVD.

Background and Aim: Barrett's esophagus is associated with increased risk of esophageal adenocarcinoma. The optimal management of low-grade dysplasia arising in Barrett's esophagus remains controversial. We performed a retrospective study from a tertiary referral center for Barrett's esophagus neoplasia, to estimate time to progression to high-grade dysplasia/esophageal adenocarcinoma in patients with confirmed low-grade dysplasia compared with those with downstaged low-grade dysplasia from index presentation and referral. We analyzed risk factors for progression., Methods: We analyzed consecutive patients with low-grade dysplasia in Barrett's esophagus referred to a single tertiary center (July 2006-October 2018). Biopsies were reviewed by at least two expert pathologists., Results: One hundred and forty-seven patients referred with suspected low-grade dysplasia were included. Forty-two of 133 (32%) of all external referrals had confirmed low-grade dysplasia after expert histopathology review. Multivariable analysis showed nodularity at index endoscopy ( P  < 0.05), location of dysplasia ( P  = 0.05), and endoscopic therapy after referral ( P  = 0.09) were associated with progression risk. At 5 years, 59% of patients with confirmed low-grade dysplasia had not progressed versus 74% of patients in the cohort downstaged to non-dysplastic Barrett's esophagus., Conclusion: Our data show variability in the diagnosis of low-grade dysplasia. The cumulative incidence of progression and time to progression varied across subgroups. Confirmed low-grade dysplasia had a shorter progression time compared with the downstaged group. Nodularity at index endoscopy and multifocal low-grade dysplasia were significant risk factors for progression. It is important to differentiate these high-risk subgroups so that decisions on surveillance/endotherapy can be personalized., (© 2021 The Authors. JGH Open published by Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd.)

Background: Although nighttime reflux symptoms are common, the presence of nocturnal reflux is seldom confirmed with a standard 24 hours pH study., Aim: To study patients with supine nighttime reflux symptoms using prolonged wireless pH monitoring., Methods: In this retrospective study, patients with typical acid reflux symptoms were studied using 96-h pH monitoring. Patients with nighttime reflux symptoms were compared to those without. Night-to-night variability and diagnostic accuracy of 24-, 48- and 72-hours pH studies compared to the 96-hours "gold standard" were evaluated., Results: Of the 105 included patients (61.9% females; mean age 46.8 ± 14.4 years), 86 (81.9%) reported nighttime reflux symptoms, of which 67.4% had pathological supine nocturnal acid exposure in at least one night. There was high variance in night-to-night acid exposure (94% [IQR0-144]), which was larger than the variance in upright acid exposure (58% [IQR32-88]; P < 0.001). When analysing the first 24 hours of the pH study, 32% of patients were diagnosed with pathological supine nighttime acid exposure versus 51% of patients based upon the 96-hours pH-test. The diagnostic accuracy and yield improved with study duration (P < 0.001). Reflux episodes with a lower nadir pH or longer acid clearance time were more prone to provoke nightly symptoms., Conclusions: The majority of patients with nocturnal reflux symptoms had pathological acid exposure in at least one night of the prolonged pH recording. A high night-to-night variability in acid exposure reduces the clinical value and diagnostic yield of pH monitoring limited to 24 hours. Prolonged testing is a more appropriate diagnostic tool for patients with nocturnal reflux symptoms., (© 2021 The Authors. Alimentary Pharmacology & Therapeutics published by John Wiley & Sons Ltd.)

Achalasia is a rare esophageal motility disorder characterized by the incomplete relaxation of the lower esophageal sphincter (LES) and impaired peristaltic activity. The advent of high-resolution manometry (HRM) and the rapidly evolving role of therapeutic endoscopy have revolutionized the approach to the diagnosis and management of achalasia patients in the last decade. With advances in HRM technology and methodology, fluoroscopy and EndoFlip, achalasia can be differentiated into therapeutically meaningful phenotypes with a high degree of accuracy. Further, the newest treatment option, per-oral endoscopic myotomy (POEM), has become a staple therapy following the last 10 years of experience, and recent randomized trials appear to show no difference between POEM, graded pneumatic dilatation and surgical Heller myotomy in terms of short- and long-term efficacy or complication rate. On the other hand, how treatment outcomes are measured as well as the risk of reflux following therapy remain areas of contention. This review aims to summarize the recent advancements in achalasia testing and therapy, describes the recent randomized clinical trials as well as their potential setbacks, and touches on the future of personalizing achalasia treatment., Competing Interests: Conflict of interest statement: The authors declare that there is no conflict of interest., (© The Author(s), 2021.)

Dysphagia is a common symptom which can vary in severity and aetiology; at one end, it can be a benign inconvenience, on the other, there can be serious morbidity associated with malnutrition. It is crucial to identify those with mucosal and structural disease, including malignancy as a priority first. Reflux disease is commonly a culprit and treating empirically with acid reducing medicines should follow exclusion of organic disease. Other benign conditions (including eosinophilic oesophagitis) should be considered. The clinical assessment of dysphagia begins with a detailed history and a focus on symptom severity as well as the pre-test probability of a given condition. Tests are then directed at assessing function, and should employ both high-resolution manometry and barium studies. For motility disorders, begin by assessing the oesophago-gastric junction for obstruction (eg achalasia), followed by oesophageal body function. The latter is divided into major and minor motility disorders. Treatment is directed according to the dysmotility phenotype and is based upon background fitness, age and appetite to intervention. Invasive treatment for achalasia is aimed at disrupting the lower oesophageal sphincter muscle while that of oesophageal body disorders is directed at reducing hypercontraction, improving peristalsis or reducing symptoms., (© Royal College of Physicians 2021. All rights reserved.)

Background & Aims: Wireless pH monitoring measures esophageal acid exposure time (AET) for up to 96 hours. We evaluated competing methods of analysis of wireless pH data., Methods: Adult patients with persisting reflux symptoms despite acid suppression (n = 322, 48.5 ± 0.9 years, 61.7% women) from 2 tertiary centers were evaluated using symptom questionnaires and wireless pH monitoring off therapy, from November 2013 through September 2017; 30 healthy adults (control subjects; 26.9 ± 1.5 years; 60.0% women) were similarly evaluated. Concordance of daily AET (physiologic <4%, borderline 4%-6%, pathologic>6%) for 2 or more days constituted the predominant AET pattern. Each predominant pattern (physiologic, borderline, or pathologic) in relation to data from the first day, and total averaged AET, were compared with other interpretation paradigms (first 2 days, best day, or worst day) and with symptoms., Results: At least 2 days of AET data were available from 96.9% of patients, 3 days from 90.7%, and 4 days from 72.7%. A higher proportion of patients had a predominant pathologic pattern (31.4%) than control subjects (11.1%; P = .03). When 3 or more days of data were available, 90.4% of patients had a predominant AET pattern; when 2 days of data were available, 64.1% had a predominant AET pattern (P < .001). Day 1 AET was discordant with the predominant pattern in 22.4% of patients and was less strongly associated with the predominant pattern compared with 48 hour AET (P = .059) or total averaged AET (P = .02). Baseline symptom burden was higher in patients with a predominant pathologic pattern compared with a predominant physiologic pattern (P = .02)., Conclusions: The predominant AET pattern on prolonged wireless pH monitoring can identify patients at risk for reflux symptoms and provides gains over 24 hours and 48 hours recording, especially when results from the first 2 days are discordant or borderline., (Copyright © 2020 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Background and study aims  Cryoablation with the Cryoballoon device is a novel ablative therapy that uses cycles of freezing and thawing to induce cell death. This single-center prospective study evaluated the feasibility of the focal cryoablation device for the treatment of areas of refractory esophageal neoplasia in patients who had undergone first line endoscopic eradication therapy (EET). Complete remission of dysplasia (CR-D) and complete remission of intestinal metaplasia (CR-IM) at first follow-up endoscopy, durability of disease reversal, rates of stenosis and adverse events were studied. Patients and methods  Eighteen cases were treated. At baseline, nine patients had low-grade dysplasia (LGD), six had high-grade dysplasia (HGD) and three had intramucosal carcinoma (IMC). Median length of dysplastic Barrett's esophagus (BE) treated was 3 cm. The median number of ablations per patient was 11. Each selected area of visible dysplasia received 10 seconds of ablation. One session of cryoablation was performed per patient. Biopsies were performed at around 3 months post-ablation. Results  CR-D was achieved in 78 % and CR-IM in 39 % of patients. There were no device malfunction or adverse events. Stenosis was noted in 11 % of cases. At a median follow up of 19-months, CR-D was maintained in 72 % of patients and CR-IM in 33 %. Conclusions  Cryoablation appears to be a viable rescue strategy in patients with refractory neoplasia. It is well tolerated and successful in obtaining CR-D and CR-IM in patients with treatment-refractory BE. Further trials of dosimetry, efficacy and safety in treatment-naïve patients are underway., Competing Interests: Competing interests The authors declare that they have no conflict of interest.

Background: Gastric antral vascular ectasia (GAVE) is a rare cause of gastrointestinal bleeding, often causing iron deficiency anaemia. Previous studies have looked at the management of this with argon plasma coagulation, laser therapy and endoscopic band ligation., Methods: This was a single-centre prospective study to evaluate the efficacy and safety of radiofrequency ablation (RFA) in patients with GAVE with persistent anaemia refractory to at least one session of first-line endoscopic therapy. Patients were treated with a through-the-scope (TTS) radiofrequency catheter at two endoscopic sessions six weeks apart. The primary outcome was change in haemoglobin at six months posttreatment. The secondary outcomes were reduction in blood or iron requirements, endoscopic surface area regression and complications., Results: Twenty patients were treated. The mean change in haemoglobin at six months was +12.6 g/l (95% confidence interval 11.7-24.3 g/l), paired t test p  < 0.001. At six months, three of 14 individuals who had required blood transfusions had ongoing blood transfusions and five of 17 who had required iron had ongoing iron needs. Surface area regression was scored as 74% ± 25% but no correlation was seen between this and other outcomes. Three of 20 patients experienced pain which was managed with oral analgesia. Of the 14 patients who had reached 12-month follow-up, three required retreatment (21%)., Discussion: This small study suggests that RFA is a safe and effective treatment for GAVE. Our study uses the TTS catheter compared to other studies, and demonstrates prolonged improvement in haemoglobin and reduction in blood and iron requirements with a novel assessment of surface area regression.

Aim: To assess clinical outcomes for submucosal (T1b) oesophageal adenocarcinoma (OAC) patients managed with either surgery or endoscopic eradication therapy., Methods: Patients found to have T1b OAC following endoscopic resection between January 2008 to February 2016 at University College London Hospital were retrospectively analysed. Patients were split into low-risk and high-risk groups according to established histopathological criteria and were then further categorised according to whether they underwent surgical resection or conservative management. Study outcomes include the presence of lymph-node metastases, disease-specific mortality and overall survival., Results: A total of 60 patients were included; 22 patients were surgically managed (1 low-risk and 21 high-risk patients) whilst 38 patients were treated conservatively (12 low-risk and 26 high-risk). Overall, lymph node metastases (LNM) were detected in 10 patients (17%); six of these patients had undergone conservative management and LNM were detected at a median of 4 mo after endoscopic mucosal resection (EMR). All LNM occurred in patients with high-risk lesions and this represented 21% of the total high-risk lesions. Importantly, there was no statistically significant difference in tumor-related deaths between those treated surgically or conservatively ( P = 0.636) and disease-specific survival time was also comparable between the two treatment strategies ( P = 0.376)., Conclusion: T1b tumours without histopathological high-risk markers of LNM can be treated endoscopically with good out-comes. In selected patients, endoscopic therapy may be appropriate for high-risk lesions., Competing Interests: Conflict-of-interest statement: The authors declare no conflicts of interest.

Oesophageal physiology testing plays an important role in the diagnosis of noncardiac chest pain (NCCP) after cardiac, structural and mucosal abnormalities have been ruled out. Endoscopy can establish the presence of structural causes of chest pain such as cancer, oesophageal webs and diverticula. Even if macroscopically normal, eosinophilic oesophagitis is a common cause of chest pain and needs to be ruled out with an adequate biopsy regimen. In the remaining cases, diagnosis is focused on the identification of often subtle mechanisms that lead to NCCP. The most common oesophageal aetiologies for NCCP are gastro-oesophageal reflux disease (GORD), oesophageal dysmotility and functional chest pain. Ambulatory pH studies (with or without impedance or wireless measurements) can establish the presence of GORD, nonerosive reflux as well any association with symptoms of chest pain. High-resolution manometry, particularly with the inclusion of adjunctive testing, can rule out major motility disorders such as spasm, hypercontraction or achalasia. The EndoFLIP device can help define disorders with reduced distensibility, not easily appreciated with endoscopy or manometry. When all tests remain negative, a diagnosis of oesophageal hypersensitivity is normally made and therapy is shifted from targeting a disease to treating symptoms and patient affect., Competing Interests: Conflict of interest statement: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Dysphagia is a common symptom that is important to recognise and appropriately manage, given that causes include life threatening oesophageal neoplasia, oropharyngeal dysfunction, the risk of aspiration, as well as chronic disabling gastroesophageal reflux (GORD). The predominant causes of dysphagia varies between cohorts depending on the interplay between genetic predisposition and environmental risk factors, and is changing with time. Currently in white Caucasian societies adopting a western lifestyle, obesity is common and thus associated gastroesophageal reflux disease is increasingly diagnosed. Similarly, food allergies are increasing in the west, and eosinophilic oesophagitis is increasingly found as a cause. Other regions where cigarette smoking is still prevalent, or where access to medical care and antisecretory agents such as proton pump inhibitors are less available, benign oesophageal peptic strictures, Barrett's oesophagus, adeno- as well as squamous cell carcinoma are endemic. The evaluation should consider the severity of symptoms, as well as the pre-test probability of a given condition. In young white Caucasian males who are atopic or describe heartburn, eosinophilic esophagitis and gastroesophageal reflux disease will predominate and a proton pump inhibitor could be commenced prior to further investigation. Upper gastrointestinal endoscopy remains a valid first line investigation for patients with suspected oesophageal dysphagia. Barium swallow is particularly useful for oropharyngeal dysphagia, and oesophageal manometry mandatory to diagnose motility disorders., Competing Interests: Conflict-of-interest statement: nil to declare.

Competing Interests: Competing interests: None declared.

Achalasia is a rare oesophageal motility disorder predominantly causing dysphagia and regurgitation of food and fluids. Diagnosis is made typically after a combination of tests including endoscopy, barium swallow and oesophageal manometry. The advent of high-resolution manometry has led to the Chicago Classification which divided achalasia into three types. This improved the understanding of presentation, prognosis and might also help tailor therapy. Botulinum toxin has been shown to have good, but short-term efficacy. The predominant treatments include pneumatic balloon dilatation and laparoscopic Heller's myotomy, both of which have similar and durable outcomes, although the success of both reduces with time. Per-oral endoscopic myotomy (POEM) has been shown to be as effective, safe and durable as earlier treatments for achalasia; however, randomised controlled trials are lacking. Indications for POEM are expanding to other hypercontractile motility disorders of the oesophagus., Competing Interests: Competing interests: None declared.

We describe a case series of 3 patients presenting with intracardiac thrombi treated with standard anticoagulation therapy and intervention with ultrasound-accelerated thrombolysis therapy. Right-sided intracardiac thrombi portend significant mortality due to their susceptibility for embolization and pulmonary embolus despite the continuation of current standard of therapy of parenteral anticoagulation and surgical embolectomy if warranted. We demonstrate the safety and clinical efficacy of ultrasound-accelerated thrombolysis therapy with the EkoSonic Endovascular System infusion catheter system (EKOS Corporation) and highlight its use in resolving intracardiac thrombi and impeding the propagation of pulmonary emboli.

Investigators from the Children's Hospital of Philadelphia analyzed the clinical and radiographic findings in 12 cases of cavernous sinus thrombosis (CST) seen between 2000 and 2013, and conducted a literature search and review of the pooled data.

Background & Aims: Management of patients with dysphagia, regurgitation, and related symptoms after antireflux surgery is challenging. This prospective, case-control study tested the hypothesis that compared with standard high-resolution manometry (HRM) with single water swallows (SWS), adding multiple water swallows (MWS) and a solid test meal increases diagnostic yield and clinical impact of physiological investigations., Methods: Fifty-seven symptomatic and 12 asymptomatic patients underwent HRM with SWS, MWS, and a solid test meal. Dysphagia and reflux were assessed by validated questionnaires. Diagnostic yield of standard and full HRM studies with 24-hour pH-impedance monitoring was compared. Pneumatic dilatation was performed for outlet obstruction on HRM studies. Clinical outcome was assessed by questionnaires and an analogue scale with "satisfactory" defined as at least 40% symptom improvement requiring no further treatment., Results: Postoperative esophagogastric junction pressure was similar in all groups. Abnormal esophagogastric junction morphology (double high pressure band) was more common in symptomatic than in control patients (13 of 57 vs 0 of 12, P = .004). Diagnostic yield of HRM was 11 (19%), 11 (19%), and 33 of 57 (58%), with SWS, MWS, and solids, respectively (P < .001); it was greatest for solids in patients with dysphagia (19 of 27, 70%). Outlet obstruction was present in 4 (7%), 11 (19%), and 15 of 57 patients (26%) with SWS, MWS, and solids, respectively (P < .009). No asymptomatic control had clinically relevant dysfunction on solid swallows. Dilatation was performed in 12 of 15 patients with outlet obstruction during the test meal. Symptom response was satisfactory, good, or excellent in 7 of 12 (58%) with no serious complications., Conclusions: The addition of MWS and a solid test meal increases the diagnostic yield of HRM studies in patients with symptoms after fundoplication and identifies additional patients with outlet obstruction who benefit from endoscopic dilatation., (Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Background/aims: The diagnosis of functional heartburn is important for management, however it stands on fragile pH monitoring variables, ie, acid exposure time varies from day to day and symptoms are often few or absent. Aim of this study was to investigate consistency of the diagnosis of functional heartburn in subsequent days using prolonged wireless pH monitoring and its impact on patients' outcome., Methods: Fifty proton pump inhibitotor refractory patients (11 male, 48 years [range, 38-57 years]) with a diagnosis of functional heartburn according to Rome III in the first 24 hours of wireless pH monitoring were reviewed. pH variables were analysed in the following 24-hour periods to determine if tracings were indicative of diagnosis of non-erosive reflux disease (either acid exposure time > 5% or normal acid exposure time and symptom index ≥ 50%). Outcome was assessed by review of hospital files and/or telephone interview., Results: Fifteen out of 50 patients had a pathological acid exposure time after the first day of monitoring (10 in the second day and 5 in subsequent days), which changed their diagnosis from functional heartburn to non-erosive reflux disease. Fifty-four percent of non-erosive reflux disease vs 11% of functional heartburn patients (P < 0.003) increased the dose of proton pump inhibitors or underwent fundoplication after the pH test. Outcome was positive in 77% of non-erosive reflux disease vs 43% of functional heartburn patients (P < 0.05)., Conclusions: One-third of patients classified as functional heartburn at 24-hour pH-monitoring can be re-classified as non-erosive reflux disease after a more prolonged pH recording period. This observation has a positive impact on patients' management.

Study Objectives: Our prior analysis suggested that error frequency increases disproportionately with Emergency department (ED) crowding. To further characterize, we measured this association while controlling for the number of charts reviewed and the presence of ambulance diversion status. We hypothesized that errors would occur significantly more frequently as crowding increased, even after controlling for higher patient volumes., Materials and Methods: We performed a prospective, observational study in a large, community hospital ED from May to October of 2009. Our ED has full-time pharmacists who review orders of patients to help identify errors prior to their causing harm. Research volunteers shadowed our ED pharmacists over discrete 4- hour time periods during their reviews of orders on patients in the ED. The total numbers of charts reviewed and errors identified were documented along with details for each error type, severity, and category. We then measured the correlation between error rate (number of errors divided by total number of charts reviewed) and ED occupancy rate while controlling for diversion status during the observational period. We estimated a sample size requirement of at least 45 errors identified to allow detection of an effect size of 0.6 based on our historical data., Results: During 324 hours of surveillance, 1171 charts were reviewed and 87 errors were identified. Median error rate per 4-hour block was 5.8% of charts reviewed (IQR 0-13). No significant change was seen with ED occupancy rate (Spearman's rho = -.08, P = .49). Median error rate during times on ambulance diversion was almost twice as large (11%, IQR 0-17), but this rate did not reach statistical significance in univariate or multivariate analysis., Conclusions: Error frequency appears to remain relatively constant across the range of crowding in our ED when controlling for patient volume via the quantity of orders reviewed. Error quantity therefore increases with crowding, but not at a rate greater than the expected baseline error rate that occurs in uncrowded conditions. These findings suggest that crowding will increase error quantity in a linear fashion.