The independent and joint risks of alcohol consumption, smoking, and excess weight on morbidity and mortality: a systematic review and meta-analysis exploring synergistic associations

OBJECTIVE

Alcohol consumption, smoking, and excess weight independently increase the risk of morbidity/mortality. Less is known about how they interact. This research aims to quantify the independent and joint associations of these exposures across health outcomes and identify whether these associations are synergistic.

STUDY DESIGN

The protocol for this systematic review and meta-analysis was pre-registered (PROSPERO CRD42021231443).

METHODS

Medline and Embase were searched between 1 January 2010 and 9 February 2022. Eligible peer-reviewed observational studies had to include adult participants from Organisation for Co-Operation and Development countries and report independent and joint associations between at least two eligible exposures (alcohol, smoking, and excess weight) and an ICD-10 outcome (or equivalent). For all estimates, we calculated the synergy index (SI) to identify whether joint associations were synergistic. Meta-analyses were conducted for outcomes with sufficiently homogenous data.

RESULTS

The search returned 26,290 studies, of which 98 were included. Based on 138,130 participants, the combined effect (SI) of alcohol and smoking on head and neck cancer death/disease was 3.78 times greater than the additive effect of each exposure (95% confidence interval [CI] = 2.61, 5.48). Based on 2,603,939 participants, the combined effect of alcohol and excess weight on liver disease/death was 1.55 times greater than the additive effect of each exposure (95% CI = 1.33, 1.82).

CONCLUSION

Synergistic associations suggest the true population-level risk may be underestimated. In the absence of bias, individuals with multiple risks would experience a greater absolute risk reduction from an intervention that targets a single exposure than individuals with a single risk.

Emerging and Established Therapeutic Approaches for Nonalcoholic Fatty Liver Disease

PURPOSE

Nonalcoholic fatty liver disease (NAFLD), more recently referred to as metabolic-associated fatty liver disease, refers to a disease spectrum ranging from hepatic steatosis to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis, associated with hepatic complications (including liver fibrosis, cirrhosis, and hepatocellular carcinoma) and extrahepatic complications (particularly cardiometabolic complications, including type 2 diabetes and cardiovascular disease). Treatment options include lifestyle interventions (dietary modification and physical activity programs) and pharmacologic interventions. Treatment aims should be broad, with a hepatic focus (to improve/reverse hepatic inflammation, fibrosis, and steatohepatitis), ideally with additional extrahepatic effects affecting metabolic co-morbidities (eg, insulin resistance, glucose dysregulation, dyslipidemia), causing weight loss and affording cardiovascular protection. NASH and fibrosis represent the main histopathological features that warrant treatment to prevent disease progression. Despite a paucity of established treatments, the array of potential molecular targets, pathways, and potential treatments is continually evolving. The goal of this article was to provide a narrative review summarizing the emerging and more established therapeutic options considering the complex pathophysiology of NAFLD and the important long-term sequelae of this condition.

METHODS

The literature was reviewed by using PubMed, conference abstracts, and press releases from early-phase clinical studies to provide an overview of the evidence.

FINDINGS

As understanding of the pathophysiology of NASH/NAFLD evolves, drugs with different mechanisms of action, targeting different molecular targets and aberrant pathways that mediate hepatic steatosis, inflammation, and fibrosis, have been developed and are being tested in clinical trials. Pharmacologic therapies fall into 4 main categories according to the molecular targets/pathways they disrupt: (1) meta-bolic targets, targeting insulin resistance, hepatic de novo lipogenesis, or substrate utilization; (2) inflam-matory pathways, inhibiting inflammatory cell recruitment/signaling, reduce oxidative/endoplasmic reticulum stress or are antiapoptotic; (3) the liver-gut axis, which modulates bile acid enterohepatic circulation/signaling or alters gut microbiota; and (4) antifibrotic targets, targeting hepatic stellate cells, decrease collagen deposition or increase fibrinolysis.

IMPLICATIONS

Lifestyle modification must remain the cornerstone of treatment. Pharmacologic treatment is reserved for NASH or fibrosis, the presence of which requires histopathological confirmation. The disease complexity provides a strong rationale for combination therapies targeting multiple pathways simultaneously.

Current and Emerging Biomarkers and Imaging Modalities for Nonalcoholic Fatty Liver Disease: Clinical and Research Applications

PURPOSE

Nonalcoholic fatty liver disease (NAFLD) is a metabolic disorder that frequently coexists with obesity, metabolic syndrome, and type 2 diabetes. The NAFLD spectrum, ranging from hepatic steatosis to nonalcoholic steatohepatitis, fibrosis, and cirrhosis, can be associated with long-term hepatic (hepatic decompensation and hepatocellular carcinoma) and extrahepatic complications. Diagnosis of NAFLD requires detection of liver steatosis with exclusion of other causes of chronic liver disease. Screening for NAFLD and identification of individuals at risk of end-stage liver disease represent substantial challenges that have yet to be met. NAFLD affects up to 25% of adults, yet only a small proportion will progress beyond steatosis to develop advanced disease (steatohepatitis and fibrosis) associated with increased morbidity and mortality. Identification of this cohort has required the gold standard liver biopsy, which is both invasive and expensive. The use of serum biomarkers and noninvasive imaging techniques is an area of significant clinical relevance. This narrative review outlines current and emerging technologies for the diagnosis of NAFLD, nonalcoholic steatohepatitis, and hepatic fibrosis.

METHODS

We reviewed the literature using PubMed and reviewed national and international guidelines and conference proceedings to provide a comprehensive overview of the evidence.

FINDINGS

Significant advances have been made during the past 2 decades that have enhanced noninvasive assessment of NAFLD without the need for liver biopsy. For the detection of steatosis, abdominal ultrasonography remains the first-line investigation, although a controlled attenuation parameter using transient elastography is more sensitive. For detecting fibrosis, noninvasive serum markers of fibrosis and algorithms based on routine biochemistry are available, in addition to transient elastography. These techniques are well validated and have been incorporated into national and international screening guidelines. These approaches have facilitated more judicious use of liver biopsy but are yet to entirely replace it. Although serum biomarkers present a pragmatic and widely available screening approach for NAFLD in large population-based studies, magnetic resonance imaging techniques offer the benefit of achieving high degrees of accuracy in disease grading, tumor staging, and assessing therapeutic response.

IMPLICATIONS

This diagnostic clinical and research field is rapidly evolving; increasingly combined applications of biomarkers and transient elastography or imaging of selective (intermediate or high risk) cases are being used for clinical and research purposes. Liver biopsy remains the gold standard investigation, particularly in the context of clinical trials, but noninvasive options are emerging, using multimodality assessment, that are quicker, more tolerable, more widely available and have greater patient acceptability.

The Impact of Macronutrient Intake on Non-alcoholic Fatty Liver Disease (NAFLD): Too Much Fat, Too Much Carbohydrate, or Just Too Many Calories?

Non-alcoholic fatty liver disease (NAFLD) is a growing epidemic, in parallel with the obesity crisis, rapidly becoming one of the commonest causes of chronic liver disease worldwide. Diet and physical activity are important determinants of liver fat accumulation related to insulin resistance, dysfunctional adipose tissue, and secondary impaired lipid storage and/or increased lipolysis. While it is evident that a hypercaloric diet (an overconsumption of calories) promotes liver fat accumulation, it is also clear that the macronutrient composition can modulate this risk. A number of other baseline factors modify the overfeeding response, which may be genetic or environmental. Although it is difficult to disentangle the effects of excess calories vs. specifically the individual effects of excessive carbohydrates and/or fats, isocaloric, and hypercaloric dietary intervention studies have been implemented to provide insight into the effects of different macronutrients, sub-types and their relative balance, on the regulation of liver fat. What has emerged is that different types of fat and carbohydrates differentially influence liver fat accumulation, even when diets are isocaloric. Furthermore, distinct molecular and metabolic pathways mediate the effects of carbohydrates and fat intake on hepatic steatosis. Fat accumulation appears to act through impairments in lipid storage and/or increased lipolysis, whereas carbohydrate consumption has been shown to promote liver fat accumulation through de novo lipogenesis. Effects differ dependent upon carbohydrate and fat type. Saturated fat and fructose induce the greatest increase in intrahepatic triglycerides (IHTG), insulin resistance, and harmful ceramides compared with unsaturated fats, which have been found to be protective. Decreased intake of saturated fats and avoidance of added sugars are therefore the two most important dietary interventions that can lead to a reduction in IHTG and potentially the associated risk of developing type 2 diabetes. A healthy and balanced diet and regular physical activity must remain the cornerstones of effective lifestyle intervention to prevent the development and progression of NAFLD. Considering the sub-type of each macronutrient, in addition to the quantity, are critical determinants of liver health.

Can routine blood tests be modelled to detect advanced liver disease in the community: model derivation and validation using UK primary and secondary care data

OBJECTIVES

Most patients are unaware they have liver cirrhosis until they present with a decompensating event. We therefore aimed to develop and validate an algorithm to predict advanced liver disease (AdvLD) using data widely available in primary care.

DESIGN, SETTING AND PARTICIPANTS

Logistic regression was performed on routinely collected blood result data from the University Hospital Southampton (UHS) information systems for 16 967 individuals who underwent an upper gastrointestinal endoscopy (2005-2016). Data were used to create a model aimed at detecting AdvLD: 'CIRRhosis Using Standard tests' (CIRRUS). Prediction of a first serious liver event (SLE) was then validated in two cohorts of 394 253 (UHS: primary and secondary care) and 183 045 individuals (Care and Health Information Exchange (CHIE): primary care).

PRIMARY OUTCOME MEASURES

Model creation dataset: cirrhosis or portal hypertension. Validation datasets: SLE (gastro-oesophageal varices, liver-related ascites or cirrhosis).

RESULTS

In the model creation dataset, 931 SLEs were recorded (5.5%). CIRRUS detected cirrhosis or portal hypertension with an area under the curve (AUC) of 0.90 (95% CI 0.88 to 0.92). Overall, 3044 (0.8%) and 1170 (0.6%) SLEs were recorded in the UHS and CHIE validation cohorts, respectively. In the UHS cohort, CIRRUS predicted a first SLE within 5 years with an AUC of 0.90 (0.89 to 0.91) continuous, 0.88 (0.87 to 0.89) categorised (crimson, red, amber, green grades); and AUC 0.84 (0.82 to 0.86) and 0.83 (0.81 to 0.85) for the CHIE cohort. In patients with a specified liver risk factor (alcohol, diabetes, viral hepatitis), a crimson/red cut-off predicted a first SLE with a sensitivity of 72%/59%, specificity 87%/93%, positive predictive value 26%/18% and negative predictive value 98%/99% for the UHS/CHIE validation cohorts, respectively.

CONCLUSION

Identification of individuals at risk of AdvLD within primary care using routinely available data may provide an opportunity for earlier intervention and prevention of liver-related morbidity and mortality.

Systematic review of the impact of non-alcoholic fatty liver disease on mortality and adverse clinical outcomes for individuals with chronic kidney disease

OBJECTIVES

To investigate if non-alcoholic fatty liver disease (NAFLD) impacts mortality and adverse outcomes for individuals with chronic kidney disease (CKD).

DESIGN

Systematic review.

DATA SOURCES

PubMed, EMBASE and Web of Science were searched up to 1 February 2020 with no restriction on the earliest date.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Observational cohort studies that reported either the risk of all-cause mortality, incidence of non-fatal cardiovascular events (CVE) or progression of kidney disease among adults with established CKD who have NAFLD compared with those without.

DATA EXTRACTION AND SYNTHESIS

Two reviewers extracted data and assessed bias independently.

RESULTS

Of 2604 records identified, 3 studies were included (UK (n=852), South Korea (n=1525) and USA (n=1413)). All were judged to have a low or moderate risk of bias. Data were insufficient for meta-analysis. Two studies examined the influence of NAFLD on all-cause mortality. One reported a significant positive association for NAFLD with all-cause mortality for individuals with CKD (p<0.05) (cardiovascular-related mortality p=ns), which was lost following adjustment for metabolic risk factors; the second reported no effect in adjusted and unadjusted models. The latter was the only study to report outcomes for non-fatal CVEs and observed NAFLD to be an independent risk factor for this (propensity-matched HR=2.00, p=0.02). Two studies examined CKD progression; in one adjusted rate of percentage decline in estimated glomerular filtration rate per year was found to be increased in those with NAFLD (p=0.002), whereas the other found no significant difference.

CONCLUSIONS

Few studies have examined the influence of NAFLD on prognosis and major adverse clinical outcomes within the CKD population. The studies identified were diverse in design and results were conflicting. This should be a focus for future research as both conditions continue to rise in prevalence and have end-stage events associated with significant health and economic costs.

PROSPERO REGISTRATION NUMBER

CRD42020166508.

Treating alcohol-related liver disease from a public health perspective

Herein, we describe the evolving landscape of alcohol-related liver disease (ALD) including the current global burden of disease and cost to working-aged people in terms of death and disability, in addition to the larger spectrum of alcohol-related heath complications and its wider impact on society. We further review the most effective and cost-effective public health policies at both a population and individual level. Currently, abstinence is the only effective treatment for ALD, and yet because the majority of ALD remains undetected in the community abstinence is initiated too late to prevent premature death in the majority of cases. We therefore hope that this review will help inform clinicians of the "public health treatment options" for ALD to encourage engagement with policy makers and promote community-based hepatology as a speciality, expanding our patient cohort to allow early detection, and thereby a reduction in the enormous morbidity and mortality associated with this disease.

IL-12 and IL-15 induce the expression of CXCR6 and CD49a on peripheral natural killer cells

INTRODUCTION

Murine hepatic NK cells exhibit adaptive features, with liver-specific adhesion molecules CXCR6 and CD49a acting as surface markers.

METHODS

We investigated human liver-resident CXCR6+ and CD49a+ NK cells using RNA sequencing, flow cytometry, and functional analysis. We further assessed the role of cytokines in generating NK cells with these phenotypes from the peripheral blood.

RESULTS

Hepatic CD49a+ NK cells could be induced using cytokines and produce high quantities of IFNγ and TNFα, in contrast to hepatic CXCR6+ NK cells. RNA sequencing of liver-resident CXCR6+ NK cells confirmed a tolerant immature phenotype with reduced expression of markers associated with maturity and cytotoxicity. Liver-resident double-positive CXCR6 + CD49a+ hepatic NK cells are immature but maintain high expression of Th1 cytokines as observed for single-positive CD49a+ NK cells. We show that stimulation with activating cytokines can readily induce upregulation of both CD49a and CXCR6 on NK cells in the peripheral blood. In particular, IL-12 and IL-15 can generate CXCR6 + CD49a+ NK cells in vitro from NK cells isolated from the peripheral blood, with comparable phenotypic and functional features to liver-resident CD49a+ NK cells, including enhanced IFNγ and NKG2C expression.

CONCLUSION

IL-12 and IL-15 may be key for generating NK cells with a tissue-homing phenotype and strong Th1 cytokine profile in the blood, and links peripheral activation of NK cells with tissue-homing. These findings may have important therapeutic implications for immunotherapy of chronic liver disease.

Alcoholic liver disease - the extent of the problem and what you can do about it

It takes upwards of ten years for alcohol-related liver disease to progress from fatty liver through fibrosis to cirrhosis to acute on chronic liver failure. This process is silent and symptom free and can easily be missed in primary care, usually presenting with advanced cirrhosis. At this late stage, management consists of expert supportive care, with prompt identification and treatment of bleeding, sepsis and renal problems, as well as support to change behaviour and stop harmful alcohol consumption. There are opportunities to improve care by bringing liver care everywhere up to the standards of the best liver units, as detailed in the Lancet Commission report. We also need a fundamental rethink of the technologies and approaches used in primary care to detect and intervene in liver disease at a much earlier stage. However, the most effective and cost-effective measure would be a proper evidence-based alcohol strategy.

Innate and adaptive genetic pathways in HCV infection

Infection with hepatitis C virus (HCV) leads to a wide spectrum of clinical manifestations. This heterogeneity is underpinned by the host immune response and the genetic factors that govern it. Polymorphisms affecting both the innate and adaptive immunity determine the outcome of exposure. However the innate immune system appears to play a greater role in determining treatment-associated responses. Overall the effects of IFNL3/4 appear dominant over other polymorphic genes. Understanding how host genetics determines the disease phenotype has not been as intensively studied. This review summarizes our current understanding of innate and adaptive immunogenetic factors in the outcome of HCV infection. It focuses on how they relate to resolution and the progression of HCV-related liver disease, in the context of current and future treatment regimes.

Natural killer cell maturation markers in the human liver and expansion of an NKG2C+KIR+ population

BACKGROUND

Selected populations of murine natural killer (NK) cells possess memory features to haptens, cytokines, and viruses. Liver-specific adhesion molecules CXCR6 and CD49a have been identified as surface markers in mice. In people, expansion of long-lived terminally differentiated NKG2C+ populations occur in the blood after viral infection. We aimed to compare intrahepatic and blood NK cell receptor expression to determine the existence of CD49a+ and CXCR6+ NK cells in human liver and define the maturation status of NKG2C+ NK cells at this site.

METHODS

Tissue samples were taken from the liver margin of 39 patients with hepatic metastases and flushed with chelating buffer followed by collagenase or mechanical digestion. Paired peripheral blood samples were taken from 15 patients, the remainder being unpaired. Mononuclear cells were isolated by ficoll separation and cell surface staining performed for CD3, CD56, CD16, CD57, CD117, CD161, CD158a, CD158b, CD49a, CD49b, CXCR6, NKG2C, and NKp46. Statistical analysis to compare intrahepatic and blood NK cell receptor expression included the median, IQR, and Mann-Whitney U test.

FINDINGS

Frequencies of NK cell precursors were similar in the liver and the blood (0·91% [0·62-3·26] vs 0·87 [0·41-1·52]); however, expression of all later markers of maturity were reduced including CD16 (47% [40·4-61·4] vs 88·7 [82·2-93·2], p<0·0001), CD57 (30·7% [25·0-53·9] vs 73·4 [70·4-87·6], p=0·0003), and KIR (11·2% [7·5-14·5] vs 26·7 [17·3-30·8], p<0·0001). Expanded hepatic CD16- NK cells were particularly immature with reduced CD57 and increased CD161 compared with the blood. NKG2C+ NK cells were found in similar frequencies in liver and blood. The hepatic NKG2C+ population was terminally differentiated, as in the circulation, but demonstrated a three-fold increase in KIR expression compared with NKG2C- counterparts, which was not seen in the blood. As in previously published research in mice, CD49a+ and CXCR6+ NK cells were liver resident (6·5% [3·9-14·6] liver vs 2·1 [1·3-4·3] blood, p<0·0001, and 65·3 [48·1-75·2] vs 4·5 [1·43-12·12], p=0·0039, respectively). Both populations were immature, with reduced KIR expression.

INTERPRETATION

We have shown that the liver contains an expanded population of immature CD16- NK cells. These cells might traffic from the blood and then differentiate into hepatic-specific CD49a+ and CXCR6+ NK cells. The function of these subsets is unknown but their immaturity hints against memory. Terminally differentiated NKG2C+ cells show KIR expansion in the human liver and probably represent an antigen-experienced population, raising the question of whether the liver is a site of NK cell memory acquisition.

FUNDING

MRC Clinical Research Fellowship.

Nitrofurantoin immune-mediated drug-induced liver injury: a serious complication of a commonly prescribed medication

Nitrofurantoin is recommended for first line prophylaxis of recurrent urinary tract infections. Despite a number of side effects it is increasingly prescribed due to its high efficacy, low cost and minimal antimicrobial resistance. Nitrofurantoin-induced immune-mediated liver injury is a particularly serious complication, resulting in both acute hepatic failure and cirrhosis with continued use. We describe the course of two patients who recently presented to our hospital in order to highlight this.

An evaluation of patient attitudes to colonoscopy and the importance of endoscopist interaction and the endoscopy environment to satisfaction and value

OBJECTIVE

Understanding patients' attitudes to their medical experience is essential for identifying value in the patient pathway, optimizing care and use of resources. This service evaluation was undertaken to determine patients' preferences and expectations for day case colonoscopy, a common gastrointestinal procedure for which there is limited such data.

METHODS

Patients attending for elective colonoscopy were invited to complete a composite, validated dedicated endoscopy questionnaire, with Likert-scale questions and a 15-point preference (ranking) scale of domains of endoscopy care that were considered most important (1) to least important (15) as contributing to a satisfactory experience.

RESULTS

Two hundred and sixteen out of 224 patients returned questionnaires. Moderate to severe anxiety was recorded in 56% of patients, commonly with respect to anticipation of pain or the results of the procedure. The median values for ranked preference scores consistent with greatest importance for satisfaction were technical skill of the endoscopist (1), discomfort during the procedure (4), and manner of the endoscopist (5). Factors considered of relatively low importance included the single-sex environment (15) (although this was more important to female patients), noise levels (13), and explanation of delay (11). Only 14% of patients responded that they would be prepared to delay an appointment for a single-sex environment.

CONCLUSION

Patients undergoing colonoscopy highly prioritize aspects of care relating to the interaction with the endoscopist and the procedure itself. Environment factors are considered to be less important. These findings may assist in service redesign around patient-identified value within the patient pathway.

Innate immunity: a new chapter for hepatitis C

The immune response to hepatitis C virus (HCV) and the mechanisms leading to successful resolution are complex. Much work has been done on understanding the adaptive immune response to HCV due to the imperative of trying to find a vaccine. However the importance of the innate immune system is being increasingly recognized. This has culminated in the discovery of IL-28B as a key genetic element in recovery from HCV in diverse populations. This association is one of the strongest in anti-viral immunity and represents a paradigm shift in how we view the immune response to HCV infection.

A survey of patients' attitudes to upper gastrointestinal endoscopy identifies the value of endoscopist-patient interactive factors

OBJECTIVE

To determine patients' self-reported preferences and expectations for outpatient upper gastrointestinal (UGI) endoscopy, including patients' priorities in obtaining a satisfactory healthcare experience, preprocedure anxiety and its causes, and preferred staff roles.

DESIGN

A composite, dedicated endoscopy questionnaire was used. This included demographic information, validated Likert scale anxiety-related questions and a 15-point ranking scale of aspects of care (1=most important to satisfaction; 15=least important).

SETTING AND PATIENTS

Unselected patients attending for an elective UGI endoscopy at two separate units were surveyed on randomly identified days.

RESULTS

A total of 202 out of 254 patients agreed to participate (79.5%). The values identified as most important to patients included technical skill (2.8) and personal manner of the endoscopist (4.9) and the nurses and support staff (5.8), control of discomfort (5.6) and adequacy of the preprocedure explanation (5.8). The factors considered least important included noise levels (12.5), privacy (10.7) and cleanliness (8.7). Moderate to severe anxiety was recorded in half of the patient cohort, predominantly due to anticipation of pain or the results of the procedure. Most patients preferred the endoscopist to discuss the findings of the endoscopy but expressed no preferences regarding the preprocedure explanation.

CONCLUSION

Patients undergoing UGI endoscopy appear to highly prioritise aspects of care relating to interaction with the endoscopist and the procedure itself. Environmental factors are considered to have much less value. These findings may assist in service redesign around patient-centred care and the development of patient satisfaction surveys in endoscopy.

Lean thinking transformation of the unsedated upper gastrointestinal endoscopy pathway improves efficiency and is associated with high levels of patient satisfaction

BACKGROUND

Upper gastrointestinal (UGI) endoscopy is a routine healthcare procedure with a defined patient pathway. The objective of this study was to redesign this pathway for unsedated patients using lean thinking transformation to focus on patient-derived value-adding steps, remove waste and create a more efficient process. This was to form the basis of a pathway template that was transferrable to other endoscopy units.

METHODS

A literature search of patient expectations for UGI endoscopy identified patient-derived value. A value stream map was created of the current pathway. The minimum and maximum time per step, bottlenecks and staff-staff interactions were recorded. This information was used for service transformation using lean thinking. A patient pathway template was created and implemented into a secondary unit. Questionnaire studies were performed to assess patient satisfaction.

RESULTS

In the primary unit the patient pathway reduced from 19 to 11 steps with a reduction in the maximum lead time from 375 to 80 min following lean thinking transformation. The minimum value/lead time ratio increased from 24% to 49%. The patient pathway was redesigned as a 'cellular' system with minimised patient and staff travelling distances, waiting times, paperwork and handoffs. Nursing staff requirements reduced by 25%. Patient-prioritised aspects of care were emphasised with increased patient-endoscopist interaction time. The template was successfully introduced into a second unit with an overall positive patient satisfaction rating of 95%.

CONCLUSION

Lean thinking transformation of the unsedated UGI endoscopy pathway results in reduced waiting times, reduced staffing requirements and improved patient flow and can form the basis of a pathway template which may be successfully transferred into alternative endoscopy environments with high levels of patient satisfaction.