Development of novel methods of assessment in oesophageal and gastric function

The objective of this thesis was to develop new methodologies to assess upper gastro-intestinal function in health and disease. Several different technologies were studied in a range of upper gastro-intestinal diseases and adapted to try and provide more meaningful insights. The thesis has three main sections. In the first section, High Resolution Oesophageal Manometry (HRM) was used to assess unexplained upper gastro-intestinal symptoms in a group of patients referred to a tertiary centre. 46 patients were diagnosed with rumination syndrome following HRM. A retrospective review was completed of these patients case notes and HRM data. The predominant aim of this section was to identify if common mechanisms exist within rumination and its variations and to establish if the variety of presenting symptoms is due to different underlying problems or a common behavioural response to a variety of stimuli, with symptoms being dependent on the circumstance the behaviour exists in. This would support a generic biofeedback technique being useful regardless of presenting complaint. Comparing the variety of symptoms, exhibited behaviour and manometric findings, a new classification system for rumination was then developed; 1. Primary or “classical” rumination a. Increase in abdominal strain with corresponding rise in intra-gastric pressure and return of gastric contents to the mouth 2. Secondary or reflux-related rumination a. Reflux event causes the patient to respond with increase in intra-abdominal muscle strain and subsequent rumination 3. Supra-gastric belching independent of meals. a. Rise in intra-gastric pressure whilst a closed gastro-oesophageal junction, therefore producing rapid belching of air from the oesophagus without any return of gastric contents Generic biofeedback therapy was used (regardless of presenting symptoms) to control the abnormal behavioural response to symptoms. 20/46 patients reported full resolution of their symptoms and a further 13 / 46 reported improvement in their symptoms with this, while underlying mechanisms were targeted e.g. reflux with proton pump inhibitors, pain in functional dyspepsia. In the second main section of this thesis, gastro-oesophageal reflux disease (GORD) is considered. GORD is currently diagnosed by 24 hour pH studies. These are often difficult for patients to tolerate and require time off medication. A more attractive method would be for diagnosis to occur at the same time as gastroscopy. A novel instrument is the EndoFLIP® device. This measures cross-sectional area (CSA) and distensibility at the gastro-oesophageal junction (GOJ) via a long catheter with a balloon at the end that straddles the GOJ. It has been hypothesised that these measurements will be increased in those with GORD, as the GOJ is more distensible, allowing more retrograde movement of gastric contents. The aim of this section of the thesis was to establish if GOJ CSA and distensibility differentiate between healthy volunteers (HV) and GORD patients based on i) symptoms and ii) prolonged oesophageal acid exposure. 21 HV and 18 patients with GORD (based on symptoms) had EndoFLIP® measurements and wireless pH studies to assess this. 14% of HV and 50% GORD patients had pathological acid exposure. CSA and distensibility were both significantly higher in the HV’s compared to GORD patients. However, there was an inverse correlation between CSA and body mass index (BMI) which was significantly higher in the patient population. This may explain differences seen due to corresponding higher intra-abdominal pressure in those individuals with a high BMI, sub-sequentially affecting the CSA and distensibility. The complex structure of the GOJ and multiple factors involved in the pathogenesis of GORD present difficulties in using EndoFLIP® to diagnose GORD. It may find applications in other areas, such as serial measurements in single patients. In the final section of this thesis, gastric emptying is the focus and its pathogenesis in functional dyspepsia (FD). Current gastric emptying studies only find abnormalities in approximately 40% of patients with FD. Gamma scintigraphy is used in routine clinical practice for gastric emptying studies. Magnetic resonance imaging (MRI) is emerging as a modality in gastric emptying assessment and potentially provides additional information. This thesis hypothesised that standard gastric emptying studies may not be measuring the parameters reflective of underlying pathophysiology in FD. Also, most have a relatively small meal size that may be too small to trigger dysfunction. MRI may provide additional insights as can assess gastric contents and surrounding structure (unlike GS). To investigate these a 400ml test meal was utilised and gastric emptying parameters i) gastric contents volume at time 0 (GCV0, representative of early emptying), ii) gastric emptying rate at the time taken for half the meal volume to empty (GE rate @T50, representative of later emptying) and the more traditional measurement iii) time taken for half the gastric contents to empty (T50) in bopth GS and MRI studies. The hypothesis of this study is that early emptying is more rapid in FD due to impaired accommodation (therefore a lower GCV0) leading to a slower later emptying (therefore a lower GE rate @ T50). Following validation studies in a large healthy population (n=53), GS and magnetic resonance imaging (MRI) studies with a test meal of 400ml were used in 8 FD patients and 24 matched HV (from the pool of HV) . FD had a significantly lower BMI. Early emptying (represented by gastric contents volume after ingestion of meal (GCV0)) was significantly lower in GS for FD patients but higher in MRI. Time for half the meal to empty (T50) and gastric emptying rate at T50 (GE rate @T50) were similar. The difference between the two modalities was thought to be due to increased secretion production in the patients, which is measureable in MRI but not in GS. A further study with a solid component of 12 non-nutrient agar beads in addition to the liquid component was completed. 24 HV’s, 17 FD patients and 11 gastro-oesophageal reflux disease (GORD) patients were studied. FD patients and GORD patients had rapid early gastric emptying in comparison to HV in gamma scintigraphy (represented by GCV0) but higher GCV0 in MRI (significantly so between HV and GORD), suggesting increased secretion production is present in both conditions. These findings do support impaired fundal accommodation within the FD population but that other factors, such as secretion production and the rate of this in comparison to gastric emptying are important in the later stages of emptying. Further work is ongoing within the MRI department to quantify and measure the emptying of these secretions. This thesis explores how existing and new technologies can be applied to clinical conditions to identify possible pathophysiology and potential targets for treatment. Only by these ongoing efforts can we endeavour to improve the care we deliver to our patients

The small bowel and functional dyspepsia - peptide hormones and neurotransmitters

Functional dyspepsia (FD) is believed to be caused by pathophysiological changes in the upper gut. Gastro-intestinal motility, epithelial transport and signalling is associated with the metabolism of nutrients and the complex regulation of hunger and satiety. Glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) are considered “hot targets”. Both are anorexigenic, can induce nausea, and are involved in neuronal and hormonal feedback. Epithelial transport and signalling are partly controlled by the action of the neurotransmitter serotonin (5-HT). 5-HT forms the “link” between luminal stimulation and the enteric nervous system. We aimed at investigating if GLP-1, PYY and 5-HT are involved in the pathogenesis of FD. In study I and II healthy subjects were given a radiolabelled omelette during intravenous infusion of saline, PYY1-36, or PYY3-36 (study I) and saline or the GLP- 1 receptor antagonist Exendin(9-39)amide (study II) in a single-blinded, randomized design. Gastric emptying (scintigraphy), appetite ratings (VAS), and plasma concentrations of insulin, glucose, GLP-1, PYY and glucagon were studied. In study III FD patients and controls consumed two liquid meals, first a fixed amount and then until maximal satiety. Gastric emptying (paracetamol absorption test) and plasma concentrations of GLP-1, glucose and insulin were assessed as well as appetite ratings and dyspeptic symptoms. In study IV duodenal mucosal biopsies from FD patients and controls were studied for the number of 5-HT-containing cells (immunohistochemistry) and the expression of different 5-HT receptors by means of PCR. Biopsies were also mounted in Ussing chambers for evaluation of basal and 5-HT-stimulated short-circuit current. In study V duodenal biopsies from non-patients with FD and controls from a population based upper endoscopy study were evaluated immunohistochemically for Chromogranin A (CGA) as endocrine cell marker and 5-HT. Individuals with FD were further divided into epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS). PYY3-36 and PYY1-36 inhibits gastric emptying (PYY3-36 most effectively), and decreased the postprandial rise in insulin. PYY3-36 induced nausea and decreased prospective consumption. GLP-1 was involved in regulation of postprandial gastric motility, in insulin and glucose levels, and restrained glucagon secretion. Gastric emptying was not affected and we conclude that GLP-1 has a role as incretin hormone independent of gastric emptying. FD patients had normal postprandial glucose and GLP-1 concentrations. The FD-EPS subgroup had higher postprandial insulin levels compared to controls. Exogenous 5-HT induced lower short-circuit current and higher electrical resistance in FD. FD patients had higher gene expression of HTR3E and SERT and lower expression of HTR7 and TPH1. The number of 5-HT containing cells in duodenal mucosa was similar in FD patients and controls, and adults with FD had less endocrine cells and a normal number of 5-HT containing cells compared to controls. Endocrine cells was significantly decreased in the duodenal bulb in EPS but not PDS. Our results provide new evidence that altered endocrine secretion in the small bowel is part of the disease mechanism in FD, with PYY and GLP-1 as key candidates. GLP-1 specifically contributes to the development of nausea. Furthermore, FD patients have abnormal 5-HT stimulated electrolyte secretion in the duodenum with possible involvement of the 5-HT receptors 3E and 7

Development of novel methods of assessment in oesophageal and gastric function

The objective of this thesis was to develop new methodologies to assess upper gastro-intestinal function in health and disease. Several different technologies were studied in a range of upper gastro-intestinal diseases and adapted to try and provide more meaningful insights. The thesis has three main sections. In the first section, High Resolution Oesophageal Manometry (HRM) was used to assess unexplained upper gastro-intestinal symptoms in a group of patients referred to a tertiary centre. 46 patients were diagnosed with rumination syndrome following HRM. A retrospective review was completed of these patients case notes and HRM data. The predominant aim of this section was to identify if common mechanisms exist within rumination and its variations and to establish if the variety of presenting symptoms is due to different underlying problems or a common behavioural response to a variety of stimuli, with symptoms being dependent on the circumstance the behaviour exists in. This would support a generic biofeedback technique being useful regardless of presenting complaint. Comparing the variety of symptoms, exhibited behaviour and manometric findings, a new classification system for rumination was then developed; 1. Primary or “classical” rumination a. Increase in abdominal strain with corresponding rise in intra-gastric pressure and return of gastric contents to the mouth 2. Secondary or reflux-related rumination a. Reflux event causes the patient to respond with increase in intra-abdominal muscle strain and subsequent rumination 3. Supra-gastric belching independent of meals. a. Rise in intra-gastric pressure whilst a closed gastro-oesophageal junction, therefore producing rapid belching of air from the oesophagus without any return of gastric contents Generic biofeedback therapy was used (regardless of presenting symptoms) to control the abnormal behavioural response to symptoms. 20/46 patients reported full resolution of their symptoms and a further 13 / 46 reported improvement in their symptoms with this, while underlying mechanisms were targeted e.g. reflux with proton pump inhibitors, pain in functional dyspepsia. In the second main section of this thesis, gastro-oesophageal reflux disease (GORD) is considered. GORD is currently diagnosed by 24 hour pH studies. These are often difficult for patients to tolerate and require time off medication. A more attractive method would be for diagnosis to occur at the same time as gastroscopy. A novel instrument is the EndoFLIP® device. This measures cross-sectional area (CSA) and distensibility at the gastro-oesophageal junction (GOJ) via a long catheter with a balloon at the end that straddles the GOJ. It has been hypothesised that these measurements will be increased in those with GORD, as the GOJ is more distensible, allowing more retrograde movement of gastric contents. The aim of this section of the thesis was to establish if GOJ CSA and distensibility differentiate between healthy volunteers (HV) and GORD patients based on i) symptoms and ii) prolonged oesophageal acid exposure. 21 HV and 18 patients with GORD (based on symptoms) had EndoFLIP® measurements and wireless pH studies to assess this. 14% of HV and 50% GORD patients had pathological acid exposure. CSA and distensibility were both significantly higher in the HV’s compared to GORD patients. However, there was an inverse correlation between CSA and body mass index (BMI) which was significantly higher in the patient population. This may explain differences seen due to corresponding higher intra-abdominal pressure in those individuals with a high BMI, sub-sequentially affecting the CSA and distensibility. The complex structure of the GOJ and multiple factors involved in the pathogenesis of GORD present difficulties in using EndoFLIP® to diagnose GORD. It may find applications in other areas, such as serial measurements in single patients. In the final section of this thesis, gastric emptying is the focus and its pathogenesis in functional dyspepsia (FD). Current gastric emptying studies only find abnormalities in approximately 40% of patients with FD. Gamma scintigraphy is used in routine clinical practice for gastric emptying studies. Magnetic resonance imaging (MRI) is emerging as a modality in gastric emptying assessment and potentially provides additional information. This thesis hypothesised that standard gastric emptying studies may not be measuring the parameters reflective of underlying pathophysiology in FD. Also, most have a relatively small meal size that may be too small to trigger dysfunction. MRI may provide additional insights as can assess gastric contents and surrounding structure (unlike GS). To investigate these a 400ml test meal was utilised and gastric emptying parameters i) gastric contents volume at time 0 (GCV0, representative of early emptying), ii) gastric emptying rate at the time taken for half the meal volume to empty (GE rate @T50, representative of later emptying) and the more traditional measurement iii) time taken for half the gastric contents to empty (T50) in bopth GS and MRI studies. The hypothesis of this study is that early emptying is more rapid in FD due to impaired accommodation (therefore a lower GCV0) leading to a slower later emptying (therefore a lower GE rate @ T50). Following validation studies in a large healthy population (n=53), GS and magnetic resonance imaging (MRI) studies with a test meal of 400ml were used in 8 FD patients and 24 matched HV (from the pool of HV) . FD had a significantly lower BMI. Early emptying (represented by gastric contents volume after ingestion of meal (GCV0)) was significantly lower in GS for FD patients but higher in MRI. Time for half the meal to empty (T50) and gastric emptying rate at T50 (GE rate @T50) were similar. The difference between the two modalities was thought to be due to increased secretion production in the patients, which is measureable in MRI but not in GS. A further study with a solid component of 12 non-nutrient agar beads in addition to the liquid component was completed. 24 HV’s, 17 FD patients and 11 gastro-oesophageal reflux disease (GORD) patients were studied. FD patients and GORD patients had rapid early gastric emptying in comparison to HV in gamma scintigraphy (represented by GCV0) but higher GCV0 in MRI (significantly so between HV and GORD), suggesting increased secretion production is present in both conditions. These findings do support impaired fundal accommodation within the FD population but that other factors, such as secretion production and the rate of this in comparison to gastric emptying are important in the later stages of emptying. Further work is ongoing within the MRI department to quantify and measure the emptying of these secretions. This thesis explores how existing and new technologies can be applied to clinical conditions to identify possible pathophysiology and potential targets for treatment. Only by these ongoing efforts can we endeavour to improve the care we deliver to our patients

Rumination syndrome: Assessment of vagal tone during and after meals and during diaphragmatic breathing

Background: Pathophysiology of rumination syndrome (RS) is not well understood. Treatment with diaphragmatic breathing improves rumination syndrome. The aim of the study was to characterize vagal tone in patients with rumination syndrome during and after meals and during diaphragmatic breathing. Methods: We prospectively recruited 10 healthy volunteers (HV) and 10 patients with RS. Subjects underwent measurement of vagal tone using heart rate variability. Vagal tone was measured during baseline, test meal and intervention (diaphragmatic (DiaB), slow deep (SlowDB), and normal breathing). Vagal tone was assessed using mean values of root mean square of successive differences (RMSSD), and area under curves (AUC) were calculated for each period. We compared baseline RMSSD, the AUC and meal‐induced discomfort scores between HV and RS. Furthermore, we assessed the effect of respiratory exercises on symptom scores, and number of rumination episodes. Key Results: There was no significant difference in baseline vagal tone between HV and RS. During the postprandial period, there was a trend to higher vagal tone in RS, but not significantly (P > .2 for all). RS had the higher total symptom scores than HV (P < .011). In RS, only DiaB decreased the number of rumination episodes during the intervention period (P = .028), while both DiaB and SlowDB increased vagal tone (P < .05 for both). The symptom scores with the 3 breathing exercises showed very similar trends. Conclusions and inferences: Patients with RS do not have decreased vagal tone related to meals. DiaB reduced number of rumination events by a mechanism not related to changes in vagal tone

Preclinical electrogastrography in experimental pigs

Surface electrogastrography (EGG) is a non-invasive means of recording gastric myoelectric activity or slow waves from cutaneous leads placed over the stomach. This paper provides a comprehensive review of preclinical EGG. Our group recently set up and worked out the methods for EGG in experimental pigs. We gained our initial experience in the use of EGG in assessment of porcine gastric myoelectric activity after volume challenge and after intragastric administration of itopride and erythromycin. The mean dominant frequency in pigs is comparable with that found in humans. EGG in experimental pigs is feasible. Experimental EGG is an important basis for further preclinical projects in pharmacology and toxicology

Clinical measurement of gastrointestinal motility and function: who, when and which test?

Symptoms related to abnormal gastrointestinal motility and function are common. Oropharyngeal and oesophageal dysphagia, heartburn, bloating, abdominal pain and alterations in bowel habits are among the most frequent reasons for seeking medical attention from internists or general practitioners and are also common reasons for referral to gastroenterologists and colorectal surgeons. However, the nonspecific nature of gastrointestinal symptoms, the absence of a definitive diagnosis on routine investigations (such as endoscopy, radiology or blood tests) and the lack of specific treatments make disease management challenging. Advances in technology have driven progress in the understanding of many of these conditions. This Review serves as an introduction to a series of Consensus Statements on the clinical measurements of gastrointestinal motility, function and sensitivity. A structured, evidence-based approach to the initial assessment and empirical treatment of patients presenting with gastrointestinal symptoms is discussed, followed by an outline of the contribution of modern physiological measurement on the management of patients in whom the cause of symptoms has not been identified with other tests. Discussions include the indications for and utility of high-resolution manometry, ambulatory pH-impedance monitoring, gastric emptying studies, breath tests and investigations of anorectal structure and function in day-to-day practice and clinical management