Gastric relaxation in response to a soup meal in healthy subjects. A study using a barostat in the proximal stomach

Gastric Contraction Imaging System Using a 3-D Endoscope

This paper presents a gastric contraction imaging system for assessment of gastric motility using a 3-D endoscope. Gastrointestinal diseases are mainly based on morphological abnormalities. However, gastrointestinal symptoms are sometimes apparent without visible abnormalities. One of the major factors for these diseases is abnormal gastrointestinal motility. For assessment of gastric motility, a gastric motility imaging system is needed. To assess the dynamic motility of the stomach, the proposed system measures 3-D gastric contractions derived from a 3-D profile of the stomach wall obtained with a developed 3-D endoscope. After obtaining contraction waves, their frequency, amplitude, and speed of propagation can be calculated using a Gaussian function. The proposed system was evaluated for 3-D measurements of several objects with known geometries. The results showed that the surface profiles could be obtained with an error of [Formula: see text] of the distance between two different points on images. Subsequently, we evaluated the validity of a prototype system using a wave simulated model. In the experiment, the amplitude and position of waves could be measured with 1-mm accuracy. The present results suggest that the proposed system can measure the speed and amplitude of contractions. This system has low invasiveness and can assess the motility of the stomach wall directly in a 3-D manner. Our method can be used for examination of gastric morphological and functional abnormalities.

Review article: a critical view on impaired accommodation as therapeutic target for functional dyspepsia

Several important pathophysiological mechanisms have been identified in functional dyspepsia, however a complete understanding of these mechanisms and beneficial therapeutic strategies are still lacking. Based on the currently available literature we aimed at providing a critical view on one of these pathophysiological mechanisms, impaired accommodation. Although impaired gastric accommodation is identified as a major pathophysiological mechanism, the clinical evidence supporting its role as an important therapeutic target is currently still lacking. Treatment with fundic relaxant drugs has shown conflicting results and has been rather disappointing in general. These negative findings could be explained by the fact that impaired fundic accommodation is part of a more complex disorder involving other regions of the proximal gut or by the increasing insight that central mechanisms may play an important role. Future studies of impaired accommodation should take these considerations into account.

Meal-induced gastric relaxation and emptying in horses after ingestion of high-fat versus high-carbohydrate diets

OBJECTIVE

To evaluate the effect of ingestion of a high-carbohydrate versus a high-fat meal on relaxation of the proximal portion of the stomach and subsequent gastric emptying in horses.

ANIMALS

6 healthy adult horses.

PROCEDURE

The study consisted of 2 phases. In phase I, horses were offered a high-fat (8% fat) or a high-carbohydrate (3% fat) pelleted meal (0.5 g/kg) of identical volume, caloric density, and protein content. In phase II, meals consisted of a commercial sweet feed meal (0.5 g/kg) or this meal supplemented with corn oil (12.3% fat) or an isocaloric amount of glucose (2.9% fat). Proximal gastric tone was measured by variations in volume of an intragastric bag introduced through a gastric cannula and maintained with a constant internal pressure by an electronic barostat. Rate of gastric emptying was measured simultaneously with the 13C-octanoic acid breath test. Interaction between both techniques was studied in additional experiments.

RESULTS

Meals with higher carbohydrate content induced a significantly more prolonged receptive relaxation of the proximal portion of the stomach than those with higher fat content, but the accommodation response was similar. Labeling the meals with the breath test marker influenced the accommodation response measured by the barostat. Gastric emptying rates were not significantly different between meals, although those high in carbohydrate initially emptied more slowly.

CONCLUSIONS AND CLINICAL RELEVANCE

In horses, in contrast to most species, dietary fat supplementation may not have a profound effect on gastric motility.

Drink tests in functional dyspepsia: which drink is best?

BACKGROUND

Drinking capacity is often reduced in functional dyspepsia. Drink tests may therefore have diagnostic potential. A simple drink test in combination with ultrasonography was applied in this study, the aim being to find the best drink for this test.

METHODS

On separate days, 10 patients with functional dyspepsia (FD) and 10 healthy controls (C) drank three different test meals (Nutridrink 150 kcal/100 mL, meat soup 4 kcal/100 mL and water) at a rate of 100 mL/min until maximal drinking capacity. Intragastric volume at maximal drinking capacity was determined using 3-dimensional ultrasonography.

RESULTS

Drinking capacity (P < 0.05) and intragastric volume (P < 0.01) were significantly lower in patients than in the controls with the meat soup meal, but not with Nutridrink or water. Gastric emptying distinguished significantly (P < 0.05) between patients and controls only with Nutridrink. Gastric emptying of Nutridrink was significantly correlated to the rate by which nausea was induced (P = 0.02), while gastric emptying of meat soup was significantly negatively correlated to the rate by which fullness was induced (P < 0.05). Receiver operating characteristic (ROC) analysis indicated that optimal discrimination between patients and controls was obtained by the combined test results of symptoms per intragastric volume using meat soup as the test meal.

CONCLUSION

For the non-invasive diagnosis of functional dyspepsia by a rapid drink test in combination with ultrasonography, a meat soup meal is preferable compared to Nutridrink or water.

Role of nitrergic input in mechanically and chemically induced gastric relaxation in conscious dogs

Our aim was to study a role of nitrergic input in gastric relaxation in conscious dogs. Proximal gastric motor responses to mechanical distension and chemical stimulation (a lipid meal orally) were evaluated by electronic barostat. Effect of N(G)-monomethyl-L-arginine acetate (L-NMMA, 5 mg/kg) on these responses was studied. When mechanical stimulation was applied, we observed steep linear increases in intragastric pressure up to about 6 mmHg, then continued to increase gradually, and could be increased still further upon the addition of L-NMMA. Oral application of a lipid led to a prompt fall in intragastric pressure (gastric receptive relaxation; GRR). Lipid treatment also led to a considerable increase in gastric volume (means +/- S.D., 150.0 +/- 50.2 ml), this was followed by a plateau phase and a gradual return to baseline levels. Neither GRR nor the associated increase in gastric volume (167.6 +/- 53.0 ml) was sensitive to treatment with L-NMMA. Our conclusion is that nitrergic input is necessary for mechanically induced gastric relaxation, but not for either GRR or chemically-induced gastric relaxation in conscious dogs.

An impaired accommodation of the proximal stomach to a meal is associated with symptoms after distal gastrectomy

OBJECTIVE

The aim of this study was to assess gastric emptying and postprandial proximal gastric tone variations depending on the presence of postoperative symptoms after Billroth II gastrectomy (BII).

METHODS

A total of 16 consecutive patients were prospectively studied 10 +/- 3 months after distal gastrectomy for antral cancer. No evidence of cancer recurrence was detected at the time of the study. Ten patients were asymptomatic after surgery, whereas six patients were considered as symptomatic because of at least one weekly epigastric pain, postprandial fullness, nausea, or vomiting. The fasting fundus volume and tone, the onset of a gastric relaxation after a standard 200-kcal liquid meal, and the characteristics of this relaxation (delay of occurrence, amplitude) were determined with a barostat. Patient results were compared to normal values obtained in 12 healthy volunteers. Gastric emptying studies were performed in all patients using the C(13) acid octanoic breath test after a 250-kcal meal.

RESULTS

In the patients, both fasting fundus tone (BII 7.0 +/- 0.5, controls 8.4 +/- 2.4 mm Hg) and volume (BII 108 +/- 11, controls 119 +/- 29 ml) were not different from controls. Fasting fundus tone was lower in asymptomatic patients than in symptomatic patients (6.5 +/- 0.4 vs 8.1 +/- 0.5 mm Hg, p < 0.04). Gastric relaxation was observed immediately after the meal in all asymptomatic patients as well as in controls. In contrast, gastric relaxation occurred in only two of six symptomatic patients (p < 0.01); when it occurred it was delayed by the meal and was observed only 23 +/- 1 min after food intake. When a relaxation occurred, its amplitude was higher than that observed in controls both in asymptomatic and symptomatic patients (294 +/- 21 vs 179 +/- 53 ml, p < 0.02).

CONCLUSIONS

After distal gastrectomy, gastric accommodation is impaired (i.e., absent or delayed) in symptomatic patients. When relaxation exists in these patients, its amplitude is higher than in control subjects.

In vivo characterization of 5-HT1A receptor-mediated gastric relaxation in conscious dogs

Accumulating data have been published emphasizing the important role of 5-hydroxytryptamine (5-HT) receptors in proximal stomach relaxation. However, a proper in vivo characterization of 5-HT receptors mediating gastric relaxation is still missing. In the current study, we focus on the in vivo characterization of 5-HT1A receptors mediating relaxation of the proximal stomach in conscious dogs. Beagle dogs were equipped with a gastric fistula. In the conscious state, volume changes within an intragastric bag were measured at constant pressure by means of a barostat. Results are presented as the maximum volume increase after treatment (mean+/-s.e.m.). All drugs were injected intravenously. The 5-HT1A receptor agonist flesinoxan (10, 50, 100 and 150 microg kg-1) induced a dose-dependent relaxation of the canine proximal stomach (50+/-10, 230+/-51, 290+/-38 and 275+/-33 ml, respectively; n=9-11). The selective 5-HT1A receptor antagonist WAY-100635 dose-dependently inhibited the flesinoxan-induced relaxation. NG-nitro-l-arginine methyl ester did not affect this relaxation, suggesting that nitrergic nerves are not involved. After supradiaphragmatic vagotomy, the baseline of the intragastric volume was larger compared to that before vagotomy (317+/-50 vs 142+/-28 ml, respectively; n=5). Compensation for this by either reduction of the intraballoon pressure or infusion of a contractile dose of bethanechol did not establish a condition in which flesinoxan was able to relax the stomach. In contrast, nitroprusside induced a significant gastric relaxation when tone was increased by bethanechol. It is concluded that flesinoxan induces proximal gastric relaxation in conscious dogs via 5-HT1A receptors. The response is mediated through a vagal pathway without involvement of nitrergic nerves.

Gastric motility: comparison of assessment with real-time MR imaging or barostat measurement initial experience

Measurements of gastric volume and motility with magnetic resonance (MR) imaging were compared with simultaneously performed measurements with a barostat in six healthy volunteers. Three-dimensional volume and two-dimensional dynamic MR images and barostat measurements were obtained at rest. Alterations in gastric volume and motility were induced by means of infusion of glucagon and erythromycin, respectively. There is strong evidence to have the opinion that MR imaging is as accurate as barostat measurement in determining changes in gastric volume, and it yields additional information about gastric contractions.

Prospective study of the effect of laparoscopic hemifundoplication on motor and sensory function of the proximal stomach

BACKGROUND

Some 30 per cent of patients develop dyspeptic symptoms following antireflux surgery. These symptoms may result from alterations in the motor and sensory function of the proximal stomach.

METHODS

Proximal gastric motor and sensory function was studied with an electronic barostat in 12 patients with reflux who underwent laparoscopic hemifundoplication. In addition, 24-h pHmetry, gastric emptying (scintigraphy) and vagus nerve integrity (pancreatic polypeptide response to hypo-glycaemia) were assessed. Fifteen healthy volunteers served as controls.

RESULTS

Laparoscopic hemifundoplication significantly decreased total acid exposure time (P < 0.05). Vagus nerve function remained intact in all but one patient. The mean(s.e.m.) lag phase for emptying of solids was significantly shorter after operation than before (15(3) versus 21(3) min; P < 0.05). Proximal gastric compliance was not significantly different before and after fundoplication. However, mean(s.e.m.) postprandial relaxation was significantly reduced (P < 0.05) after hemifundoplication compared with the value before operation (3341(1105) versus 12 763(3616) ml over 90 min) and in controls (14 567(2358) ml over 90 min). Postprandial fullness was significantly increased after hemi-fundoplication (P < 0.05). Postprandial gastric relaxation correlated with the lag phase for emptying of solids (r = 0.55, P < 0.02).

CONCLUSION

After hemifundoplication, proximal gastric compliance is not altered but postprandial relaxation is impaired and associated with sensations of fullness and shorter duration of the lag phase for emptying of solids.

Standards for diagnosis of gastrointestinal motility disorders. Section: ultrasonography. A position statement from the Gruppo Italiano di Studio Motilità Apparato Digerente

Ultrasonography is a non-invasive, relatively easy, validated and reproducible technique. We assessed the usefulness of functional ultrasonography to study disorders of gastro-oesophageal tract, gallbladder and pancreatic duct. Oesophagus Oesophagus and the gastro-oesophageal junction can be visualized in children up to 5 years old. Ultrasonography shows 100% sensitivity and 87.5% specificity compared to ambulatory pH-metry for gastro-oesophageal reflux disease diagnosis. Stomach Ultrasonography can be used to estimate whole gastric volume, antral area or diameters, antro-pyloric volume, transpyloric flow in fasting state and in response to test meal. Gallbladder Ultrasonography is reliable to estimate volume in fasting state and in response to test meal or exogenous stimulus. For both stomach and gallbladder, indications might include the study of healthy subjects and of pathophysiologically relevant conditions such as dysmotility-like dyspepsia, suspicion of delayed gastric emptying, diabetes mellitus, gallstone disease and effect of drugs either delaying or accelerating motility. Common bile duct Ultrasonography can be used to estimate interprandial and postprandial common bile duct diameter in patients with clinical suspicion of common bile duct obstruction in fasting state and in response to test meal or exogenous stimuli. Although functional ultrasonography is used mainly for research purposes, its simplicity makes it appealing for clinical use to assess gastrointestinal motility in health and disease.

Effect of gastrin on proximal gastric motor function in humans

The present study was performed to investigate the effect of gastrin on proximal gastric motor and sensory function. Ten healthy volunteers participated in three experiments performed in random order during: (A) continuous intravenous infusion of saline (control) or (B) gastrin (15 pmol kg-1 h-1) reaching postprandial serum gastrin levels or (C) gastrin infusion (15 pmol kg-1 h-1) preceded by acute acid inhibition with intravenous omeprazole. Proximal gastric function was evaluated using a barostat with stepwise pressure and volume distensions and volume measurements during set pressure (MDP + 2 mmHg). Gastrin significantly increased the intragastric volume compared to control during MDP + 2 mmHg (276 +/- 39 mL vs. 159 +/- 9 mL; P < 0.01) and reduced phasic slow volume wave frequency (from 1.4 +/- 0.1 to 0.7 +/- 0.1 per min; P < 0.01). During isobaric distensions gastrin increased gastric compliance (42 +/- 4 mL mmHg-1 vs. 31 +/- 3 mL mmHg-1; P < 0.05). These effects of gastrin infusion were completely abolished by pretreatment with omeprazole. Symptom perception decreased during gastrin infusion and was more dependent on pressure and wall tension than on volume.

IN CONCLUSION

gastrin may have a role in regulating proximal gastric mechanics by inducing fundic relaxation and increasing gastric wall compliance. The effect of gastrin is dependent on acid secretion.

The role of the barostat in human research and clinical practice

BACKGROUND

The barostat is a recently developed device used to study the physiology and pathophysiology of the motor and sensory functions of the gastrointestinal tract. It can monitor volume changes while maintaining a set constant pressure and deliver controlled distensions of gastrointestinal organs. Simultaneously, motility and visceral perception may be assessed. The barostat has contributed to the understanding of physiological processes in the gastrointestinal tract with regard to regulation of tone, compliance, enteric reflexes, sensation and processing of signals to and from the gut. In addition, the barostat has been used to study various gastrointestinal disorders. In functional bowel disorders, objective abnormalities in visceral sensitivity and enteric reflexes have been demonstrated. Numerous other diseases, gastrointestinal in origin as well as systemic diseases affecting the gut, have been studied. In the near future, the barostat may become a clinically useful tool for the objective diagnosis of motor and sensitivity disorders of the gut and for monitoring the effectiveness of therapy.

Motor and sensory function of the proximal stomach in reflux disease and after laparoscopic Nissen fundoplication

OBJECTIVE

After Nissen fundoplication, dyspeptic symptoms such as fullness and early satiety develop in >30% of patients. These symptoms may result from alterations in proximal gastric motor and sensory function.

METHODS

We have evaluated proximal gastric motor and sensory function using an electronic barostat in 12 patients after successful laparoscopic Nissen fundoplications (median follow-up; 12 months). Twelve age- and gender-matched patients with severe gastroesophageal reflux disease (GERD) and 12 healthy volunteers served as controls. Studies were performed in the fasting state and after meal ingestion. Gastric emptying tests were performed in all patients. Vagus nerve integrity was measured by the response of pancreatic polypeptide (PP) to insulin hypoglycemia.

RESULTS

Minimal distending pressure and proximal gastric compliance were not significantly different between post-Nissen patients, GERD patients, and healthy controls. Postprandial relaxation of the stomach, however, was significantly (p < 0.05) reduced post-Nissen (267 +/- 34 ml), compared with controls (400 +/- 30 ml) and GERD (448 +/- 30 ml). Postprandial relaxation was significantly (p < 0.01) prolonged in GERD patients. Postprandial relaxation of the stomach correlated with gastric emptying of solids (r = 0.62; p = 0.01). Gastric emptying of solids became significantly (p < 0.05) faster after fundoplication. Postprandial fullness was significantly (p < 0.05) increased in the operated patients.

CONCLUSIONS

Post-Nissen patients have a significantly reduced postprandial gastric relaxation and significantly accelerated gastric emptying, which may explain postoperative dyspeptic symptoms. The abnormalities result from fundoplication and not from vagus nerve injury or reflux per se, because in reflux patients gastric relaxation and gastric emptying are prolonged.

Timing of postprandial dyspeptic symptoms and transpyloric passage of gastric contents

BACKGROUND

Patients with functional dyspepsia often experience early satiety and discomfort after a meal. The role of early gastric emptying in symptom generation is not known. Our aim was to relate timing of symptoms and early postprandial emptying in functional dyspepsia.

METHODS

Twelve patients with functional dyspepsia were investigated during 3 min of fasting, during 3 min of ingesting 500 ml of a meat soup, and during the first 10 min postprandially by means of duplex sonography.

RESULTS

Gastric emptying commenced on average 52 sec after the start of ingestion. Transpyloric movements of gastric contents unrelated to peristalsis (that is, alternating transpyloric emptying and reflux within a common chamber created by the terminal antrum, the pylorus, and the duodenal bulb) appeared before peristaltic-related emptying, which commenced after on average 116 sec. In all patients epigastric, meal-related discomfort was experienced after the commencement of transpyloric emptying, on average after 143 sec. A negative correlation was found between intensity of fullness and duration of presymptomatic transpyloric movements of gastric contents (that is, the duodenal 'tasting' period).

CONCLUSIONS

The early occurrence of meal-related symptoms suggests that gastric distension is the main factor in symptom generation. However, the onset of symptoms after the commencement of gastric emptying suggests that intestinal tasting receptors are involved in symptom generation. The inverse relationship between the duration of the tasting period and symptom intensity suggests that the time allowed for duodenal tasting might be too short in patients with FD.

Influence of a selective guanylate cyclase inhibitor, and of the contraction level, on nitrergic relaxations in the gastric fundus

1. The influence of the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ) on non-adrenergic non-cholinergic (NANC) relaxations and the possible role of a nerve-derived hyperpolarizing factor in NANC relaxation were investigated in the rat gastric fundus. 2. ODQ (10(-6) and 10(-5) M) concentration-dependently inhibited the short-lasting relaxations by NO (2 x 10(-6) M-10(-4) M) administered as a bolus without influencing the relaxation by 3 x 10(-8) M isoprenaline. The relaxation by an infusion of NO was reduced to the same extent by 10(-6) and 10(-5) M ODQ. 3. The electrically induced short-lasting and sustained relaxations (40 V, 1 ms, 0.5-16 Hz, 10 s trains at 2 min interval or cumulative increase in the frequency every 2 min) in NANC conditions were inhibited to a similar extent by 10(-6) and 10(-5) M ODQ, and by the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 3 x 10(-4) M). 4. ODQ (10(-6) M) and L-NAME (3 x 10(-4) M), administered after 5, 10 or 20 min of long-term stimulation, reversed the relaxation to a similar extent (approximately 50% at 2 Hz and 20% at 8 Hz). 5. When the tissues were contracted to 40% of maximum by adapting the concentration of prostaglandin F2alpha (PGF2alpha), the inhibitory effect of 3 x 10(-4) M L-NAME on relaxations induced by train and cumulative stimulation was the same as when tissues were contracted with 3 x 10(-7) M PGF2alpha. 6. The findings of this study illustrate that the relaxation by exogenous and endogenous NO in the rat gastric fundus is due to activation of soluble guanylate cyclase. During long-term electrical stimulation, the partial contribution of NO to NANC relaxation is maintained but it is small at higher frequencies of stimulation. Evidence for the contribution of a nerve-derived hyperpolarizing factor to NANC relaxation was not obtained.

Effect of CCK on proximal gastric motor function in humans

We have studied the effect of CCK on proximal gastric motor function in humans. Seven healthy volunteers participated in three experiments performed in random order during continuous intravenous infusion of 1) saline (control), 2) 0.5 IDU.kg-1.h-1 CCK, and 3) 1.0 IDU.kg-1.h-1 CCK. Proximal gastric mechanics were measured by an electronic barostat, and abdominal symptoms were scored by visual analog scales. Infusion of 0.5 and 1.0 IDU.kg-1.h-1 CCK resulted in plasma CCK levels (RIA) in the postprandial range. CCK induced gastric relaxation; at 2 mmHg above intra-abdominal pressure the intragastric volume during 1.0 IDU.kg-1.h-1 CCK was significantly increased over saline (363 +/- 44 vs. 195 +/- 34 ml; P < 0.01) but not during 0.5 IDU.kg-1.h-1 CCK (195 +/- 14 ml; not significant). During both isovolumetric and isobaric distensions, 1.0 IDU.kg-1.h-1 CCK significantly (P < 0.05) increased proximal gastric compliance compared with saline. However, 0.5 IDU.kg-1.h-1 CCK had no significant effect on gastric compliance. During volume distensions, but not during fixed pressure distensions, 1.0 IDU.kg-1.h-1 CCK significantly (P < 0.05) reduced visceral perception. These results suggest that in humans CCK may have a physiological role in regulating proximal gastric mechanics.

Impaired accommodation of proximal stomach to a meal in functional dyspepsia

In patients with functional dyspepsia, scanning by a novel ultrasonographic method was carried out to investigate postprandial accommodation of the proximal stomach. Twenty patients with functional dyspepsia and 20 controls were scanned fasting in a sitting position after drinking 500 ml meat soup. Images were recorded up to 25 min after the ingestion period using an ultrasound sector scanner with a 3.25-MHz transducer. The area in a sagittal section and the maximal diameter in a oblique frontal section were chosen as the main variables for calculating the emptying fraction of the proximal stomach, defined as: (aV2.5min - aVactual/aV2.5min. All subjects were asked to score total symptoms (1-9) provoked by the meal. From 7.5 to 25 min after the ingestion period the patients exhibited both smaller area in the sagittal section (P < 0.018) and shorter diameter in the frontal section (P < 0.046) compared with the healthy controls, and they suffered more symptoms in response to the meal (P = 0.002). Dyspeptic patients revealed higher emptying fractions (P = 0.0005, ANOVA), and H. pylori status did not influence the emptying fractions. Diagnostic sensitivity of the method at 20 min postprandially was 70% and the specificity was 65%. Patients with functional dyspepsia have impaired accommodation of the proximal stomach to a meal, temporarily related to symptom induction.