Gastroenteropancreatic neuroendocrine neoplasia (GEPNEN) comprises clinically as well as prognostically diverse tumour entities often diagnosed at late stage. Current classification provides a uniform terminology and a Ki67-based grading system, thereby facilitating management. Advances in the study of genomic and epigenetic landscapes have amplified knowledge of tumour biology and enhanced identification of prognostic and potentially predictive treatment subgroups. Translation of this genomic and mechanistic biology into advanced GEPNEN management is limited. 'Targeted' treatments such as somatostatin analogues, peptide receptor radiotherapy, tyrosine kinase inhibitors and mammalian target of rapamycin inhibitors are treatment options but predictive tools are lacking. The inability to identify clonal heterogeneity and define critical oncoregulatory pathways prior to therapy, restrict therapeutic efficacy as does the inability to monitor disease status in real time. Chemotherapy in the poor prognosis NEN G3 group, though associated with acceptable response rates, only leads to short-term tumour control and their molecular biology requires delineation to provide new and more specific treatment options.The future requires an exploration of the NEN tumour genome, its microenvironment and an identification of critical oncologic checkpoints for precise drug targeting. In the advance to personalised medical treatment of patients with GEPNEN, clinical trials need to be based on mechanistic and multidimensional characterisation of each tumour in order to identify the therapeutic agent effective for the individual tumour.This review surveys advances in NEN research and delineates the current status of translation with a view to laying the basis for a genome-based personalised medicine management of advanced GEPNEN.

We performed a meta-analysis of observational studies to quantify the magnitude of the association between non-alcoholic fatty liver disease (NAFLD) and risk of extrahepatic cancers.

Guidelines from national and international professional societies on upper gastrointestinal bleeding highlight the important clinical issues but do not always identify specific management strategies pertaining to individual patients. Optimal treatment should consider the personal needs of an individual patient and the pertinent resources and experience available at the point of care. This article integrates international guidelines and consensus into three stages of management: pre-endoscopic assessment and treatment, endoscopic evaluation and haemostasis and postendoscopic management. We emphasise the need for personalised management strategies based on patient characteristics, nature of bleeding lesions and the clinical setting including available resources.

Non-alcoholic fatty liver disease (NAFLD) has become the most common cause of chronic liver disease worldwide. Understanding the pathological and molecular hallmarks from its first description to definitions of disease entities, classifications and molecular phenotypes is crucial for both appropriate clinical management and research in this complex disease. We provide an overview through almost two hundred years of clinical research from the beginnings as a nebulous disease entity of unknown origin in the 19th century to the most frequent and vigorously investigated liver disease today. The clinical discrimination between alcohol-related liver disease and NAFLD was uncommon until the 1950s and likely contributed to the late acceptance of NAFLD as a metabolic disease entity for long time. Although the term 'fatty liver hepatitis' first appeared in 1962, it was in 1980 that the term 'non-alcoholic steatohepatitis' (NASH) was coined and the histopathological hallmarks that are still valid today were defined. The 2005 NASH Clinical Research Network scoring was the first globally accepted grading and staging system for the full spectrum of NAFLD and is still used to semiquantify main histological features. In 2021, liver biopsy remains the only diagnostic procedure that can reliably assess the presence of NASH and early fibrosis but increasing efforts are made towards non-invasive testing and molecular classification of NAFLD subtypes.

An understanding of the etiologic heterogeneity of colorectal cancer (CRC) is critical for improving precision prevention, including individualized screening recommendations and the discovery of novel drug targets and repurposable drug candidates for chemoprevention. Known differences in molecular characteristics and environmental risk factors among tumors arising in different locations of the colorectum suggest partly distinct mechanisms of carcinogenesis. The extent to which the contribution of inherited genetic risk factors for CRC differs by anatomical subsite of the primary tumor has not been examined.

Acute-on-chronic liver failure (ACLF) is characterised by acute decompensation of cirrhosis associated with organ failures. We systematically evaluated the geographical variations of ACLF across the world in terms of prevalence, mortality, aetiology of chronic liver disease (CLD), triggers and organ failures.

Anti-tumour necrosis factor (TNF) antibodies have been widely used for approximately 25 years now. The first clinical observations in patients with refractory Crohn's disease rapidly responding to infliximab prompted accelerated clinical development and approval for this indication. However, many questions remained unanswered when this treatment came to market related to maintenance schedules, pharmacokinetics, toxicity and positioning. Many of these open questions were addressed by investigators and sponsors during more than two decades of clinical use. The authors were among the first to use infliximab in Crohn's disease and felt that now is a good time to look back and draw lessons from the remarkable anti-TNF story. Even today, new insights continue to appear. But more importantly, what was learnt in the past 25 years has created a platform for future development of even stronger and safer therapies. We should not forget to learn from the past.

Intestinal resident macrophages are at the front line of host defence at the mucosal barrier within the gastrointestinal tract and have long been known to play a crucial role in the response to food antigens and bacteria that are able to penetrate the mucosal barrier. However, recent advances in single-cell RNA sequencing technology have revealed that resident macrophages throughout the gut are functionally specialised to carry out specific roles in the niche they occupy, leading to an unprecedented understanding of the heterogeneity and potential biological functions of these cells. This review aims to integrate these novel findings with long-standing knowledge, to provide an updated overview on our understanding of macrophage function in the gastrointestinal tract and to speculate on the role of specialised subsets in the context of homoeostasis and disease.

In treating patients with inflammatory bowel disease (IBD), how concomitant medications influence the response to infliximab is largely unexplored. We aim to evaluate whether proton pump inhibitors (PPIs) affect the response to infliximab therapy in patients with IBD.

Studies reported a significant association between non-alcoholic fatty liver disease (NAFLD) and increased risk of chronic kidney disease (CKD). However, whether this risk changes with increasing severity of NAFLD remains uncertain. We performed a meta-analysis of observational studies to quantify the magnitude of the association between NAFLD and risk of incident CKD.

Chronic pain is a hallmark of functional disorders, inflammatory diseases and cancer of the digestive system. The mechanisms that initiate and sustain chronic pain are incompletely understood, and available therapies are inadequate. This review highlights recent advances in the structure and function of pronociceptive and antinociceptive G protein-coupled receptors (GPCRs) that provide insights into the mechanisms and treatment of chronic pain. This knowledge, derived from studies of somatic pain, can guide research into visceral pain. Mediators from injured tissues transiently activate GPCRs at the plasma membrane of neurons, leading to sensitisation of ion channels and acute hyperexcitability and nociception. Sustained agonist release evokes GPCR redistribution to endosomes, where persistent signalling regulates activity of channels and genes that control chronic hyperexcitability and nociception. Endosomally targeted GPCR antagonists provide superior pain relief in preclinical models. Biased agonists stabilise GPCR conformations that favour signalling of beneficial actions at the expense of detrimental side effects. Biased agonists of µ-opioid receptors (MOPrs) can provide analgesia without addiction, respiratory depression and constipation. Opioids that preferentially bind to MOPrs in the acidic microenvironment of diseased tissues produce analgesia without side effects. Allosteric modulators of GPCRs fine-tune actions of endogenous ligands, offering the prospect of refined pain control. GPCR dimers might function as distinct therapeutic targets for nociception. The discovery that GPCRs that control itch also mediate irritant sensation in the colon has revealed new targets. A deeper understanding of GPCR structure and function in different microenvironments offers the potential of developing superior treatments for GI pain.

Metabolic disorders represent a growing worldwide health challenge due to their dramatically increasing prevalence. The gut microbiota is a crucial actor that can interact with the host by the production of a diverse reservoir of metabolites, from exogenous dietary substrates or endogenous host compounds. Metabolic disorders are associated with alterations in the composition and function of the gut microbiota. Specific classes of microbiota-derived metabolites, notably bile acids, short-chain fatty acids, branched-chain amino acids, trimethylamine N-oxide, tryptophan and indole derivatives, have been implicated in the pathogenesis of metabolic disorders. This review aims to define the key classes of microbiota-derived metabolites that are altered in metabolic diseases and their role in pathogenesis. They represent potential biomarkers for early diagnosis and prognosis as well as promising targets for the development of novel therapeutic tools for metabolic disorders.

Artificial intelligence (AI) can extract complex information from visual data. Histopathology images of gastrointestinal (GI) and liver cancer contain a very high amount of information which human observers can only partially make sense of. Complementing human observers, AI allows an in-depth analysis of digitised histological slides of GI and liver cancer and offers a wide range of clinically relevant applications. First, AI can automatically detect tumour tissue, easing the exponentially increasing workload on pathologists. In addition, and possibly exceeding pathologist's capacities, AI can capture prognostically relevant tissue features and thus predict clinical outcome across GI and liver cancer types. Finally, AI has demonstrated its capacity to infer molecular and genetic alterations of cancer tissues from histological digital slides. These are likely only the first of many AI applications that will have important clinical implications. Thus, pathologists and clinicians alike should be aware of the principles of AI-based pathology and its ability to solve clinically relevant problems, along with its limitations and biases.

MicroRNAs (miRNAs) are small, non-coding RNAs that post-transcriptionally regulate gene expression by binding to specific mRNA targets and promoting their degradation and/or translational inhibition. miRNAs regulate both physiological and pathological liver functions. Altered expression of miRNAs is associated with liver metabolism dysregulation, liver injury, liver fibrosis and tumour development, making miRNAs attractive therapeutic strategies for the diagnosis and treatment of liver diseases. Here, we review recent advances regarding the regulation and function of miRNAs in liver diseases with a major focus on miRNAs that are specifically expressed or enriched in hepatocytes (miR-122, miR-194/192), neutrophils (miR-223), hepatic stellate cells (miR-29), immune cells (miR-155) and in circulation (miR-21). The functions and target genes of these miRNAs are emphasised in alcohol-associated liver disease, non-alcoholic fatty liver disease, drug-induced liver injury, viral hepatitis and hepatocellular carcinoma, as well liver fibrosis and liver failure. We touch on the roles of miRNAs in intercellular communication between hepatocytes and other types of cells via extracellular vesicles in the pathogenesis of liver diseases. We provide perspective on the application of miRNAs as biomarkers for early diagnosis, prognosis and assessment of liver diseases and discuss the challenges in miRNA-based therapy for liver diseases. Further investigation of miRNAs in the liver will help us better understand the pathogeneses of liver diseases and may identify biomarkers and therapeutic targets for liver diseases in the future.

The British Society of Gastroenterology in collaboration with British Association for the Study of the Liver has prepared this document. The aim of this guideline is to review and summarise the evidence that guides clinical diagnosis and management of ascites in patients with cirrhosis. Substantial advances have been made in this area since the publication of the last guideline in 2007. These guidelines are based on a comprehensive literature search and comprise systematic reviews in the key areas, including the diagnostic tests, diuretic use, therapeutic paracentesis, use of albumin, transjugular intrahepatic portosystemic stent shunt, spontaneous bacterial peritonitis and beta-blockers in patients with ascites. Where recent systematic reviews and meta-analysis are available, these have been updated with additional studies. In addition, the results of prospective and retrospective studies, evidence obtained from expert committee reports and, in some instances, reports from case series have been included. Where possible, judgement has been made on the quality of information used to generate the guidelines and the specific recommendations have been made according to the 'Grading of Recommendations Assessment, Development and Evaluation (GRADE)' system. These guidelines are intended to inform practising clinicians, and it is expected that these guidelines will be revised in 3 years' time.

Inflammatory bowel disease and Parkinson's disease are chronic progressive disorders that mainly affect different organs: the gut and brain, respectively. Accumulating evidence has suggested a bidirectional link between gastrointestinal inflammation and neurodegeneration, in accordance with the concept of the 'gut-brain axis'. Moreover, recent population-based studies have shown that inflammatory bowel disease might increase the risk of Parkinson's disease. Although the precise mechanisms underlying gut-brain interactions remain elusive, some of the latest findings have begun to explain the link. Several genetic loci are shared between both disorders with a similar direction of effect on the risk of both diseases. The most interesting example is LRRK2 (leucine-rich repeat kinase 2), initially identified as a causal gene in Parkinson's disease, and recently also implicated in Crohn's disease. In this review, we highlight recent findings on the link between these seemingly unrelated diseases with shared genetic susceptibility. We discuss supporting and conflicting data obtained from epidemiological and genetic studies along with remaining questions and concerns. In addition, we discuss possible biological links including the gut-brain axis, microbiota, autoimmunity, mitochondrial function and autophagy.

Cirrhotic portal hypertension is characterised by development of the decompensating events of ascites, encephalopathy, portal hypertensive bleeding and hepatorenal syndrome, which arise in a setting of cirrhosis-associated immune dysfunction (CAID) and define morbidity and prognosis. CAID describes the dichotomous observations that systemic immune cells are primed and display an inflammatory phenotype, while failing to mount robust responses to pathogen challenge. Bacterial infections including spontaneous bacterial peritonitis are common complications of advanced chronic liver disease and can precipitate variceal haemorrhage, hepatorenal syndrome and acute-on-chronic liver failure; they frequently arise from gut-derived organisms and are closely linked with dysbiosis of the commensal intestinal microbiota in advanced chronic liver disease.Here, we review the links between cirrhotic dysbiosis, intestinal barrier dysfunction and deficits of host-microbiome compartmentalisation and mucosal immune homoeostasis that occur in settings of advanced chronic liver disease. We discuss established and emerging therapeutic strategies targeted at restoring intestinal eubiosis, augmenting gut barrier function and ameliorating the mucosal and systemic immune deficits that characterise and define the course of decompensated cirrhosis.

The human gut microbiome is a complex ecosystem, densely colonised by thousands of microbial species. It varies among individuals and depends on host genotype and environmental factors, such as diet and antibiotics. In this review, we focus on stability and resilience as essential ecological characteristics of the gut microbiome and its relevance for human health. Microbial diversity, metabolic flexibility, functional redundancy, microbe-microbe and host-microbe interactions seem to be critical for maintaining resilience. The equilibrium of the gut ecosystem can be disrupted by perturbations, such as antibiotic therapy, causing significant decreases in functional richness and microbial diversity as well as impacting metabolic health. As a consequence, unbalanced states or even unhealthy stable states can develop, potentially leading to or supporting diseases. Accordingly, strategies have been developed to manipulate the gut microbiome in order to prevent or revert unhealthy states caused by perturbations, including faecal microbiota transplantation, supplementation with probiotics or non-digestible carbohydrates, and more extensive dietary modifications. Nevertheless, an increasing number of studies has evidenced interindividual variability in extent and direction of response to diet and perturbations, which has been attributed to the unique characteristics of each individual's microbiome. From a clinical, translational perspective, the ability to improve resilience of the gut microbial ecosystem prior to perturbations, or to restore its equilibrium afterwards, would offer significant benefits. To be effective, this therapeutic approach will likely need a personalised or subgroup-based understanding of individual genetics, diet, gut microbiome and other environmental factors that might be involved.