Fundic accommodation assessed by SPECT scanning: comparison with the gastric barostat

Imaging in Gastroparesis: Exploring Innovative Diagnostic Approaches, Symptoms, and Treatment

Gastroparesis (GP) is a chronic disease characterized by upper gastrointestinal symptoms, primarily nausea and vomiting, and delayed gastric emptying (GE), in the absence of mechanical GI obstruction. The underlying pathophysiology of GP remains unclear, but factors contributing to the condition include vagal nerve dysfunction, impaired gastric fundic accommodation, antral hypomotility, gastric dysrhythmias, and pyloric dysfunction. Currently, gastric emptying scintigraphy (GES) is considered the gold standard for GP diagnosis. However, the overall delay in GE weakly correlates with GP symptoms and their severity. Recent research efforts have focused on developing treatments that address the presumed underlying pathophysiological mechanisms of GP, such as pyloric hypertonicity, with Gastric Peroral Endoscopic Myotomy (G-POEM) one of these procedures. New promising diagnostic tools for gastroparesis include wireless motility capsule (WMC), the 13 carbon-GE breath test, high-resolution electrogastrography, and the Endoluminal Functional Lumen Imaging Probe (EndoFLIP). Some of these tools assess alterations beyond GE, such as muscular electrical activity and pyloric tone. These modalities have the potential to characterize the pathophysiology of gastroparesis, identifying patients who may benefit from targeted therapies. The aim of this review is to provide an overview of the current knowledge on diagnostic pathways in GP, with a focus on the association between diagnosis, symptoms, and treatment.

Diagnostic Methods for Evaluation of Gastric Motility-A Mini Review

Gastric motility abnormalities are common in patients with disorders of gut-brain interaction, such as functional dyspepsia and gastroparesis. Accurate assessment of the gastric motility in these common disorders can help understand the underlying pathophysiology and guide effective treatment. A variety of clinically applicable diagnostic methods have been developed to objectively evaluate the presence of gastric dysmotility, including tests of gastric accommodation, antroduodenal motility, gastric emptying, and gastric myoelectrical activity. The aim of this mini review is to summarize the advances in clinically available diagnostic methods for evaluation of gastric motility and describe the advantages and disadvantages of each test.

A New Paradigm Shift in Gastroparesis Management

Gastroparesis, once regarded as a rare disease, is difficult to diagnose and challenging to treat; there were many breakthrough advances in the 2010s, shifting the paradigm of the understanding of this complex entity and its management. Similar to diabetes, its increasing prevalence reflects increased accessibility to diagnostic modalities and suggests that gastroparesis was underacknowledged in the past. Major developments in the three main aspects of the disease include the discovery of smooth muscle cells, interstitial cells of Cajal, PDGFRα+ cells syncytium, rather than interstitial cells of Cajal alone, as the main gastric pacemaker unit; the development of validated point-of-care diagnostic modalities such as a wireless motility capsule, the carbon 13-labeled breath test, and impedance planimetry; and the introduction of novel minimally invasive therapeutic options such as newer pharmacologic agents and gastric peroral endoscopic pyloromyotomy. All aspects of these advances will be discussed further in this review.

Gastric accommodation: Physiology, diagnostic modalities, clinical relevance, and therapies

BACKGROUND

Gastric accommodation is an essential gastric motor function which occurs following ingestion of a meal. Impaired gastric fundic accommodation (IFA) is associated with dyspeptic symptoms. Gastric accommodation is mediated by the vagal pathway with several important physiologic factors such as duodenal nutrient feedback playing a significant role. IFA has been described as a pathophysiologic factor in several gastrointestinal disorders including functional dyspepsia, diabetic gastropathy, post-Nissen fundoplication, postsurgical gastrectomy, and rumination syndrome. Modalities for gastric accommodation assessment include gastric barostat, intragastric meal distribution via scintigraphy, drinking tests (eg, water load), SPECT, MRI, 2D and 3D ultrasound, and intragastric high-resolution manometry. Several treatment options including sumatriptan, buspirone, tandospirone, ondansetron, and acotiamide may improve symptoms by increasing post-meal gastric volume.

PURPOSE

Our aim is to provide an overview of the physiology, diagnostic modalities, and therapies for IFA. A literature search was conducted on PubMed, Google Scholar, and other sources to identify relevant studies available until December 2020. Gastric accommodation is an important gastric motor function which if impaired, is associated with several upper gastrointestinal disorders. There are an increasing number of gastric accommodation testing modalities; however, each has facets which warrant consideration. Evidence regarding potentially effective therapies for IFA is growing.

Assessment of Gastric Accommodation in Patients with Functional Dyspepsia by 99mTc-Pertechtenate Single Photon Emission Computed Tomography Imaging: Practical but not Widely Accepted

Objective:

Impaired gastric accommodation is one of the main symptoms in patients with functional dyspepsia. The aim of the present study was to assess gastric accommodation in patients with functional dyspepsia using single photon emission computed tomography (SPECT) imaging.

Methods:

Twenty-four patients with functional dyspepsia and 50 healthy volunteers as control group were enrolled in this study. All participants were given 5 mCi 99mTc-pertechtenate intravenously, served with a low fat meal, and underwent SPECT scanning 20 minutes after the meal.

Results:

Based on the scintigraphic data, gastric volumes were found to be significantly increased after food ingestion in both patient and control groups. We also found that while there was no significant difference between patient and control groups in terms of fasting gastric volumes, postprandial gastric volume was significantly lower in patients as compared to healthy individuals (p<0.05).

Conclusion:

Measuring gastric volume by using SPECT can be a valuable method in the detection of functional dyspepsia and in differentiation of this entity from other organic disorders.

Gastrointestinal tone; its genesis and contribution to the physical processes of digestion

BACKGROUND

Myogenic tone has long been recognised as an important component of gastrointestinal motility. Recent work has clarified the cellular mechanisms that engender tone and the neurogenic and mechanical stimuli that modulate it but has also highlighted cellular and regional specialisation in these mechanisms within the GI tract. Smooth muscle in all segments of the gut has the capability of latching, i.e. can generate ongoing specific rather than tetanic tone. This is likely modulated by both direct and indirect input from agonists such as acetylcholine and mechanoreceptors, the latter originating in ICC-IM, smooth muscle cells or elements of the ENS. Tonic contraction can occur in the absence of phasic contractions or concurrent with them, and it can modulate wall compliance and the capacity of particular segments, thereby affecting the level of on-flow and mixing, both luminal and adjacent to the mucosa.

PURPOSE

The review seeks to provide an overview of our understanding of the mechanism by which tone is generated and maintained, highlighting its modulation by neurogenic and mechanical stimuli, its mechanical consequences in the walls of the various segments of the gastrointestinal tract and its contribution to flow and mixing of contained digesta.

Use of scintigraphy to evaluate gastric accommodation and emptying: comparison with barostat

BACKGROUND AND AIM

Scintigraphy is a useful noninvasive technique for assessment of gastric motility, especially emptying, but there is little knowledge of use of the technique to assess gastric accommodation. Therefore, to clarify the usefulness of scintigraphy as a technique for assessing gastric accommodation, we compared scintigraphy with barostat, the gold standard modality.

METHODS

Twenty healthy volunteers (14 men, six women; mean age, 28.5 ± 5.4 years) were enrolled in the study. The volunteers ingested a radiolabeled ((99m) Tc) test meal and scintigraphic images were recorded. Radioactivity in the upper third and whole stomach was calculated to evaluate accommodation. In the barostat procedure, gastric accommodation was evaluated by measuring the maximum volume of the distended balloon. Thereafter, correlation between scintigraphic and barostat accommodation was investigated. Intra-and inter-observer variation of the scintigraphic test results were also assessed. Finally, the diagnostic performance of scintigraphy was evaluated by using sumatriptan as a positive control.

RESULTS

Measurements of accommodation by scintigraphy and barostat correlated (r = 0.524, P < 0.05). Sumatriptan significantly increased scintigraphically measured gastric accommodation (with sumatriptan, 51.5 ± 16.4%; without sumatriptan, 38.4 ± 13.8%) (P < 0.01), and had significantly (P < 0.05) delayed 50% half emptying time at 60, 90, 120, and 150 min after the start of the experiment. The data from repeated scintigraphic tests were highly reproducible (r = 0.804) with significant differences not observed among the investigators (inter-observer variation = 0.932, intra-observer variation = 0.898).

CONCLUSION

Gastric scintigraphy is a useful technique for assessing gastric accommodation and emptying.

Effect of the GLP-1 analog liraglutide on satiation and gastric sensorimotor function during nutrient-drink ingestion

BACKGROUND/AIM

Liraglutide, a glucagon-like peptide-1 analog, induces weight loss. We investigated whether liraglutide affects gastric accommodation and satiation by measuring the intragastric pressure (IGP) during nutrient-drink consumption and using the barostat technique.

METHODS

Ten healthy volunteers (HVs) were tested after placebo, 0.3, 0.6 or 1.2 mg liraglutide administration. IGP was studied during intragastric nutrient-drink (1.5 kcal ml(-1)) infusion (60 ml min(-1)), while the HVs scored their satiation on a graded scale until maximal satiation. In a separate session, isobaric distentions were performed using the barostat with stepwise increments of 2 mm Hg starting from minimal distending pressure, although HVs scored their perception; gastric volume was monitored 30 min before and until 60 min after ingestion of 200 ml of nutrient drink. Data are presented as mean±s.e.m. comparisons were performed with ANOVA (P<0.05 was significant).

RESULTS

During nutrient-drink infusion, IGP decreased with 4.1±0.7, 3.0±0.4, 2.1±0.3 and 2.6±0.4 mm Hg (placebo, 0.3, 0.6 and 1.2 mg liraglutide, respectively; P<0.05). The maximum-tolerated volume was not different, except after treatment with 1.2 mg liraglutide (695±135 ml) compared with placebo (1008±197 ml; P<0.05); however, 1.2 mg liraglutide induced nausea in all volunteers. In the barostat study, liraglutide did not affect the perception or compliance, but significantly decreased gastric accommodation to the meal (168±27 vs 78.8±36.4 ml after treatment with placebo and 0.6 mg liraglutide, respectively; P<0.05).

CONCLUSION

Although no effect on perception, compliance or satiation was observed, liraglutide inhibited gastric accommodation. Whether this effect is involved in the anorectic effect of liraglutide remains to be determined.

Investigating functional dyspepsia in Asia

The diagnosis of functional dyspepsia (FD) is challenging since it depends largely on symptoms which are often heterogeneous and overlapping. This is particularly so in Asia with many different cultures and languages. Symptom-based diagnosis of FD based on Rome III criteria has not been fully validated and it may not be suitable in some Asian populations. Clinicians often assume that investigations in FD are not rewarding and physiological tests are often not available unless in the research setting. Investigation of alarm features and role of Helicobacter pylori in FD remain controversial but experts agreed that both should be tested. Physiological tests including gastric accommodation and chemical hypersensitivity tests are underutilized in Asia and available studies were few. While experts do not recommend routine clinical use of gastric accommodation tests but they agree that these tests can be advocated if clinically indicated. Empiric therapeutic trial is not currently a diagnostic option. The pathogenesis of FD is still poorly understood and there is a substantial placebo response. As a conclusion, a diagnosis of FD is challenging especially so in the context of Asia and despite the limitations of available physiological tests experts agreed that these tests can be advocated if and when clinically indicated.

Measurement of gastric accommodation: a reappraisal of conventional and emerging modalities

Impaired gastric accommodation is an important cause of functional dyspepsia. Currently available tests that evaluate gastric accommodation provide relevant physiological information, but they pose technical difficulties and their clinical impact remains controversial. Gastric barostat remains the gold standard, but it is an invasive procedure. In recent years, emerging modalities including single photon emission computed tomography (SPECT), three-dimensional ultrasound and magnetic resonance imaging have been developed to measure gastric volumes and hold promise as alternative methods of assessing gastric accommodation non-invasively. Studies are underway to validate these techniques with recent data proving the performance characteristics of SPECT. The non-invasive nutrient drink test measures satiety scores as a surrogate marker of gastric accommodation and remains controversial. More recently, intragastric monitoring has been proposed as yet another non-invasive modality to assess gastric accommodation. Each of these different modalities brings its associated advantages and disadvantages, as is discussed in this review. Ongoing studies to validate these new techniques are in progress and are likely to lead to further progress in neurogastroenterology.

Efficacy of mosapride citrate in proximal gastric accommodation and gastrointestinal motility in healthy volunteers: a double-blind placebo-controlled ultrasonographic study

BACKGROUND

Mosapride citrate, a 5-hydroxytryptamine-4 receptor agonist, enhances antral contractions and gastric emptying, but its effects on proximal gastric accommodation and gastroduodenal motility have not been fully studied. The aim of the present study was to clarify the effects of mosapride citrate on proximal gastric accommodation and gastroduodenal motility in healthy volunteers, using ultrasonography.

METHODS

Fourteen healthy volunteers (mean age 25.3 years) were treated for 14 days with mosapride citrate (15 mg b.d.) or a placebo in a double-blind randomized fashion. Before and after drug treatment, ultrasonographic assessment of gastroduodenal motility was performed. For assessment of the gastric accommodation reflex, the cross-sectional area of the proximal stomach was measured after the incremental ingestion, with a straw, of up to 400 ml of a liquid meal (consommé soup: 13.1 kcal, 400 ml); this was done with the subject in a supine position. Gastric emptying, antral contractions, and the duodenogastric reflux were observed as described previously.

RESULTS

In the subjects treated with mosapride citrate, the expansion rate of the cross-sectional area of the proximal stomach was significantly greater after the ingestion of 400 ml as compared to that of the subjects treated with the placebo. Similarly, gastric emptying and antral contractions increased significantly in the mosapride citrate group as compared to the placebo group. Although the duodenogastric reflux tended to decrease in the mosapride citrate group, it showed no significant difference between the two groups.

CONCLUSIONS

This study shows that mosapride citrate enhances the meal-induced gastric accommodation reflex and promotes adequate gastroduodenal coordination and motility in healthy volunteers.

The Reproducibility of Tc-Pertechnetate Single Photon Emission Computed Tomography (SPECT) for Measurement of Gastric Accommodation in Healthy Humans: Evaluation of the Test Results Performed at the Same Time and Different Time of the Day

Background/Aims

Technetium-99m (^99mTc)-pertechnetate single photon emission computed tomography (SPECT) allows non-invasive measurement of gastric accommodation (GA) and has been reported to provide the results comparable to the gold standard barostat. The reproducibility of the test when it is performed at different time of the day is not known. The aim of this study was to assess the reproducibility of GA measurement by ^99mTc-pertechnetate SPECT at the same and different time of the day.

Methods

Three GA studies were performed in each of 20 healthy volunteers (9 males, age 35 ± 9 years), 2 studies in the morning and 1 study in the afternoon. Each study was performed on separate days at least 3 days apart, in random order. The fasting gastric scintigraphy images were acquired using SPECT at 30 minutes after iv ^99mTc-pertechnetate. Then, the scintigraphic images were acquired 50 minutes after liquid meal (250 mL, Ensure®) ingestions. Gastric volumes were calculated from transaxial gastric images using Image J software. The GA was defined as the maximum postprandial gastric volume minus fasting gastric volume.

Results

GA measurement by SPECT show good reproducibility at both the same and different time of the day. The intraclass correlation coefficients of GA results for the same time, the first different time and the second different time studies were 0.681, 0.630 and 0.774, respectively, and the intra-subject coefficients of variation were 13.9%, 14.1% and 8.7%, respectively.

Conclusions

GA measurement by ^99mTc-pertechnetate SPECT shows good reproducibility at both the same and different time of the day. This result suggests that the schedule time does not appear to extremely affect the gastric accommodation value.

Efficacy of Rikkunshito, a traditional Japanese medicine (Kampo), in treating functional dyspepsia

BACKGROUND

Rikkunshito, a traditional Japanese (Kampo) medicine, is widely prescribed as an oral preparation for the treatment of functional dyspepsia (FD). In our previous study, we reported that extracorporeal ultrasonography (US) is a useful technique for the assessment of the gastric accommodation reflex (AR) and duodenogastric motility. In this study, we examined the effects of Rikkunshito on the gastroduodenal function in patients with FD.

METHODS

Sixteen FD patients (median age, 45 y) underwent US, before and after 14 days of treatment with Rikkunshito (7.5 g b.d.). For assessment of the AR, a cross-sectional area of the proximal stomach was measured after incremental ingestion of a liquid meal up to 400-mL. The expansion rate was used as the parameter to determine the AR. Then, the gastric emptying rate (GER), motility index (MI), and reflux index (RI) were evaluated using previously reported methods.

RESULTS

Although no significant changes were observed in the total score of the Gastrointestinal Symptom Rating Scale (GSRS), the scores of 3 of the 15 symptoms of GSRS decreased significantly after treatment with Rikkunshito. The expansion rate of the proximal stomach was significantly greater after treatment with Rikkunshito than before the treatment. Although the GER and MI increased significantly, no significant differences in the RI were observed after treatment with Rikkunshito.

CONCLUSION

These observations suggested that Rikkunshito may be beneficial for the treatment of FD patients with impaired AR and gastric motility. These results also suggested that Rikkunshito has a therapeutic potential for FD and GERD.

Selected interventions in nuclear medicine: gastrointestinal motor functions

The measurement of gastrointestinal functions by the use of scintigraphy is established in clinical practice and research. The most commonly used test is the gastric-emptying test, which is acknowledged as the gold standard to measure gastric motility and is conducted according to a consensus statement from the national nuclear medicine and motility societies. Other techniques are somewhat more esoteric (eg, measurement of gastric accommodation with single-photon emission computed tomography) or the scintigraphic approach is not the acknowledged gold standard (eg, colonic transit, rectoanal angle, and emptying, esophageal transit). The performance characteristics of many of the scintigraphic measurements have been published and the pros and cons established in the literature. Pharmacologic interventions may also be used during scintigraphy to aid in diagnosis and treatment. Gastrointestinal scintigraphy is an integral and important component of the assessment of gastrointestinal function.

Mandatory and optional function tests in gastroduodenal disorders

A number of patients have symptoms suggestive of a disturbance of gastroduodenal function. Current gastric function tests allow us to study gastric emptying, motor activity, gastroduodenal sensitivity to distention and accommodation to a meal. The best application of these tests seems to be in the explanation of symptoms. However, most of the available tests have a low diagnostic specificity, and their results usually have no major impact on the choice of therapy. In rare or refractory cases, small bowel manometry may lead to specific diagnoses and gastric emptying testing may prompt the decision to consider more invasive therapies. Gastroduodenal function tests do not seem to predict the response to therapy or the prognosis of patients with presumed gastric sensory or motor disorders. The main limitation to a greater clinical usefulness of gastroduodenal function testing is the lack of therapeutic alternatives.

Gastrointestinal motility testing

Gastrointestinal motility and the effects on luminal contents that are brought about by it can be studied in several ways. In clinical practice, manometry remains one of the most important investigational techniques, in particular for oesophageal and anorectal disorders. Radiographic examination of bolus transit through the gastrointestinal tract also continues to be a valuable tool. Scintigraphy still is the gold standard for assessment of gastric emptying, but (13)(C) breath tests are an alternative. Many other techniques are used mainly in the context of scientific research but some of these may become incorporated in the diagnostic armamentarium.

Effects of the H2-receptor antagonist ranitidine on gastric motor function after a liquid meal in healthy humans

OBJECTIVE

Studies on animals have shown that histamine may be involved in the regulation of gastrointestinal smooth muscle tone. However, the role of histamine in the regulation of human gastric motor function is not clear. This study examined the effect of ranitidine, an H(2)-receptor antagonist, on gastric volume and gastric emptying after a liquid meal in healthy humans.

MATERIAL AND METHODS

Twelve healthy volunteers participated in a randomized crossover study with 50 mg ranitidine as a bolus intravenously versus no medication. Gastric volume at baseline was determined with single photon emission computed tomography (SPECT) after intravenous injection of 99(m)Tc-pertechnetate. After ingestion of a 600-mL liquid meal radiolabelled with (111)In-diethylenetriaminepentaacetic acid, dual-isotope technique with SPECT and planar imaging assessed gastric volume as well as gastric emptying.

RESULTS

Ranitidine did not change gastric volume before the meal, nor at 0 h or 1 h after it. Furthermore, ranitidine did not influence gastric retention of meal components after 0.5 h and 1 h.

CONCLUSIONS

Intravenous bolus injection of 50 mg ranitidine does not modify gastric volume or gastric emptying after a 600 mL liquid meal in healthy humans.

Application of magnetic resonance imaging to measure fasting and postprandial volumes in humans

Our aims were to measure the gastric volume response in excess of ingested meal volume (i.e. gastric accommodation), contribution of swallowed air to this excess, day-to-day variability of gastric volumes measured by MRI and their relationship to volumes measured by single-photon-emission computed tomography (SPECT). In 20 healthy volunteers, fasting and postprandial gastric volumes were measured after technetium(99m)-pertechnetate labeling of the gastric mucosa by SPECT and separately by MRI, using 3D gradient echo and 2D half-Fourier acquisition single-shot turbo spin echo (HASTE) sequences. Ten of these subjects had a second MRI exam to assess intra-individual variation. Thereafter, another 10 subjects had two MRI studies during which they ingested the nutrient in 30 or 150 mL aliquots. During MRI, the postprandial gastric volume change exceeded the ingested meal volume by 106 +/- 12 mL (Mean +/- SEM). The HASTE and gradient echo sequences distinguished air from fluid under fasting and postprandial conditions respectively. This postprandial excess mainly comprised air (61 +/- 5 mL), which was not significantly different when ingested as 30 or 150 mL aliquots. Fasting and postprandial gastric volumes measured by MRI were generally reproducible within subjects. During SPECT, postprandial volumes increased by 158 +/- 18 mL; gastric volumes measured by SPECT were higher than MRI. MRI measures gastric volumes with acceptable performance characteristics; the postprandial excess primarily consists of air, which is not affected by the mode of ingestion. Gastric volumes are technique specific and differ between MRI and SPECT.

Effect of the 5-HT3 receptor antagonist, ondansetron, on gastric size in dyspeptic patients with impaired gastric accommodation

BACKGROUND

A reduction of gastric accommodation after a meal has been documented in patients with idiopathic dyspepsia. In these patients the administration of a 5-HT3 receptor antagonist may reduce some of the dyspeptic symptoms; it is not clear however, whether these drugs influence gastric adaptation to distension as well.

AIM

To evaluate the effects of the 5-HT3 receptor antagonist, ondansetron, on gastric distension after a liquid meal in dyspeptic patients with reduced gastric accommodation.

METHODS

Before and after a 500 ml water load, gastric accommodation (area of the proximal and distal stomach) was evaluated using real-time ultrasonography in 21 idiopathic dyspepsia patients and 26 healthy controls. In dyspeptic patients, the test was repeated twice: after the administration of placebo and after ondansetron 8 mg i.v. (in both cases, 15 min prior to the water load). Secondary outcomes were epigastric pain, fullness and nausea as assessed by a visual analogue scale at basal and after ondansetron.

RESULTS

Fasting gastric size was similar in dyspeptic and controls. Compared with controls, dyspeptic patients showed a statistically significant smaller area of the proximal stomach (14.7+/-1.2 cm(2) vs. 18.6+/-1.4 cm(2), respectively; p=0.0247). In dyspeptic patients, gastric proximal and distal size did not change significantly following placebo, whereas after the administration of ondansetron the mean area of the proximal and distal stomach significantly increased (proximal stomach: 14.6+/-1.6 cm(2) placebo, 20.4+/-1.9 cm(2) ondansetron, p=0.0095; distal stomach: 8.9+/-0.9 placebo, 11.4+/-1.2cm(2) ondansetron, p=0.0409). Of the symptoms, only nausea was significantly reduced after ondansetron.

CONCLUSION

In dyspeptic patients with impaired gastric accommodation, ondansetron reverts gastric accommodation to within the range of controls.

Impaired drinking capacity in patients with functional dyspepsia: intragastric distribution and distal stomach volume

The water drink test is a good tool to evoke dyspeptic symptoms. To what extent these symptoms are related to altered gastric distribution is not clear. Therefore, we determined gastric volumes after a drink test using SPECT. After a baseline scan 20 healthy volunteers (HV) and 18 patients with functional dyspepsia (FD) underwent a drink test (100 mL min(-1)) followed by five scans up to 2 h. Dyspeptic symptoms were scored before every scan. A Wilcoxon signed rank test (P < 0.05) and a mixed effects model were used for statistical analyses. Fasting volumes were significantly higher in FD compared to HV for total, proximal and distal stomach (P < 0.001). Functional dyspeptic patients ingested significantly less water (P < 0.001) and had an impaired filling of the distal part of the stomach (P = 0.001) after the drink test. In FD, bloating (prox. 80%, dist. 56%), pain (prox. 87%, dist. 62%) and fullness (prox. 80%, dist. 59%) were determined more by proximal stomach volume rather than distal stomach volume. These data suggest that drinking capacity is mainly determined by antral volume, with a reduced antral filling in FD compared to HV. The persisting symptoms of bloating, pain and fullness in FD are predominantly associated with proximal stomach volume.

Single photon emission computed tomography for gastric volume assessment: A method with observer-defined regions of interest

AIM

Single photon emission computed tomography (SPECT) imaging allows non-invasive measurement of gastric volume. In previous studies, the processing of the SPECT data involved global threshold algorithms that do not take into account the non-uniform distribution of radioactivity in the gastric wall. The aim of this study was to develop a simple alternative method based on observer-defined regions of interest.

METHODS

A phantom study was performed to standardize volume calculations from SPECT derived cross-sectional areas. In 12 healthy volunteers, the principle was then used to determine gastric volume before and after a 600 ml liquid meal. Furthermore, gastric emptying of the meal was followed with planar scintigraphy.

RESULTS

The median volume of the stomach was 86 ml (range 62-130 ml) at baseline, 642 ml (536-748 ml) immediately after the meal, and 370 ml (221-481 ml) 1 h after the meal. The coefficient of variation for the calculations was 9%, 2% and 4%, respectively. The median increase in gastric volume was 562 ml (501-628 ml) immediately after the meal and 294 ml (159-370 ml) after 1 h. Gastric retention of the meal was 68% (50-73%) after 0.5 h and 51% (39-57%) after 1 h.

CONCLUSIONS

The present manual technique may be a reliable alternative to the automated SPECT methods for assessing gastric volume. The liquid meal that was used in our study did not seem to cause an increase in gastric volume that differed from the volume of the meal.

Role of gastric sensorimotor dysfunction in gastrointestinal symptoms and energy intake in liver cirrhosis

OBJECTIVE

Altered gastric sensorimotor function is related to the symptomatology in several gastrointestinal diseases. Gastrointestinal symptoms in patients with cirrhosis may result in low energy intake contributing to malnutrition and increased morbidity. The aim of this study was to investigate gastric accommodation to a meal and sensitivity to gastric distension with reference to energy intake, nutritional status and gastrointestinal symptoms in liver cirrhosis.

MATERIAL AND METHODS

Sixteen patients with cirrhosis and 15 healthy controls underwent a gastric barostat study to assess gastric accommodation to a meal and sensory thresholds for first perception and discomfort. The patients also underwent a slow caloric satiety drinking test. Food intake and nutritional status were also evaluated and gastrointestinal symptoms were assessed by means of a questionnaire.

RESULTS

Compared with controls, patients with cirrhosis had enhanced gastric accommodation (p<0.05) but lower daily energy intake (p<0.05). Patients with versus those without compromised nutritional status had enhanced gastric accommodation (p<0.05). Gastric accommodation was correlated to daily energy intake in controls (r=0.67, p<0.05) but not in cirrhotic patients (p>0.4). The end-point of the satiety test was inversely related to gastric volumes in cirrhotic patients. Mean post-meal balloon volumes were positively correlated to the Model for End Stage Liver Disease (MELD) score (r=0.53, p<0.05). Sensory thresholds did not differ between patients and controls but were related to gastrointestinal symptom severity and cirrhosis severity scores in the patients.

CONCLUSIONS

Gastric accommodation is increased in cirrhotic patients but there seems to be some disturbance in its relation to energy intake. The satiety drinking test is not a good surrogate marker of accommodation in cirrhotic patients. In cirrhosis the severity of gastrointestinal symptoms is related to gastric sensitivity.

Contribution of sensitivity, volume and tone to visceral perception in the upper gastrointestinal tract in man: emphasis on testing

Upper gastrointestinal (GI) symptoms occur frequently in the general population, making them among the most common indications responsible for patients consulting the healthcare system. Consequently, understanding and characterization of the upper GI symptoms is important for the diagnosis and assessment of organ dysfunction. In practice, assessment of clinical symptoms is difficult and it is still to a large extent unclear how sensitivity, volume and tone contribute to visceral perception in the upper GI tract. The goal of advanced research in upper GI symptoms is to obtain a better understanding of the mechanisms involved in transduction, transmission, and perception under normal and pathophysiological conditions. An important step towards this goal is understanding the information provided by and the inherent limitations of the currently available measuring techniques. This article focuses on the sensory testing of the oesophagus, and methods and concepts used to assess the relation between gastric volumes or tone and upper GI symptoms. It also summarizes the contributions of these techniques towards identifying the components responsible for the generation of upper GI symptoms.

The effect of macronutrients on gastric volume responses and gastric emptying in humans: A magnetic resonance imaging study

The effects of macronutrients on gastric volume changes, emptying, and gastrointestinal symptoms are incompletely understood. Three liquid meals of 500 ml (fat emulsion, 375 kcal; protein solution, 375 kcal; glucose solution, 400 kcal) were infused into the stomach of 12 healthy volunteers on three occasions. Studies were performed in seated body position using an open-configuration magnetic resonance imaging (MRI) system. MRI imaging sequences, assessing stomach and meal volumes, were performed prior to and at times t = 0, 3, 6, 9, 12, 15, 25, 35, 45, 60, 75, and 90 min after meal administration. Areas under the curve for the early emptying phase (0-15 and 0-45 min) were calculated, and characteristics of the volume curves were analyzed by a gastric emptying model. Gastrointestinal symptoms were assessed by a self-report scale. Initial (t = 0 min) and early postprandial gastric volumes were highest for glucose because of lower initial emptying. However, in the early emptying phase the characteristics of the volume curves for stomach and meal were uniform for all macronutrients. Perceptions of fullness and satiety were linearly associated with postprandial gastric volumes, but not with macronutrient composition. Isovolumic macronutrient meals modulate gastric volume response by initial meal emptying patterns. Macronutrient specific accommodation responses, as shown in barostat studies, are not reflected as gastric volume responses under noninvasive conditions.

Gastric accommodation and motility are influenced by the barostat device: Assessment with magnetic resonance imaging

The barostat is considered the gold standard for evaluation of proximal gastric motility especially for the accommodation response to a meal. The procedure is invasive because it involves the introduction of an intragastric catheter and bag and is not always well tolerated. Moreover, the barostat bag itself may influence motility. Nowadays magnetic resonance imaging (MRI) is able to measure several aspects of gastric motility noninvasively. To evaluate whether the accommodation response of the stomach, observed with the barostat, is present during MRI and whether the barostat interferes with gastric physiology, gastric accommodation, motility, and emptying were studied twice in 14 healthy subjects with MRI using three-dimensional volume scans and two-dimensional dynamic scans once in the presence of a barostat bag and once when the barostat bag was not present. Fasting and postprandial intragastric volumes were significantly higher in the experiment with barostat vs. without barostat (fasting: 350 +/- 132 ml vs. 37 +/- 21 ml, P < 0.0001; postprandial: 852 +/- 126 ml vs. 361 +/- 62 ml, P < 0.0001). No significant differences were found in gastric emptying (88 +/- 41 vs. 97 +/- 40 ml/h, not significant) and contraction frequency between both experiments. The accommodation response observed in the presence of the barostat bag was not observed in the absence of the barostat bag. In conclusion, the presence of an intragastric barostat bag does not interfere with gastric emptying or motility, but the accommodation response measured with the barostat in situ is not observed without the barostat bag in situ. Gastric accommodation is a nonphysiological barostat-induced phenomenon.

Fundal dysaccommodation in functional dyspepsia: head-to-head comparison between the barostat and three-dimensional ultrasonographic technique

BACKGROUND

Recently, non-invasive techniques such as 3 dimensional ultrasonography (3DUS) have been developed to assess gastric wall characteristics and to investigate their relationship with upper gastrointestinal sensations. To date, no head-to-head comparison has been carried out between the barostat and the 3DUS technique.

AIM

To compare barostat and 3DUS and to investigate the relationship between gastric volumes and sensations in patients with functional dyspepsia and in healthy subjects.

PATIENTS AND METHODS

Gastric accommodation was studied in 15 patients with functional dyspepsia and in 15 healthy subjects after ingestion of a liquid nutrient (300 kcal) using barostat and 3DUS in random order for 60 min. Proximal gastric relaxation was measured using barostat and gastric volume using 3DUS. Change in gastric volume, acquired by 3DUS, was expressed as total gastric volume/proximal volume ratio (TGV/PV) and compared with changes in barostat volume (fundal accommodation).

RESULTS

Patients with functional dyspepsia showed a smaller change in proximal gastric volume than healthy subjects using barostat (mean (SD) 82 (61) v 205 (79) ml, p<0.01) and 3DUS (118 (41) v 199 (39) ml, p<0.01). Dysaccommodation of the proximal stomach was observed in 7 of 15 (46%) patients using the barostat technique. 10 of 15 (67%) patients were found to have an abnormal change in proximal gastric volume using TGV/PV ratio. At 5 min postprandially, fullness was related to the change in distal gastric volume (r = 0.51, p = 0.006) in the 3DUS study, whereas no relationship was observed in the barostat study.

CONCLUSION

3DUS is a feasible non-invasive technique to measure gastric volumes and shows a distinct overlap with barostat data in healthy subjects and patients with functional dyspepsia. Fullness relates to distal gastric volumes when assessed by non-invasive 3DUS.

Impaired gastric accommodation and its role in dyspepsia

The accommodation reflex is an important mechanism of normal gastric physiology. In functional dyspepsia, impairment of accommodation has been found in 40% of cases, but it has been described in several other upper gastrointestinal disorders, such as diabetic gastropathy and postfundoplication syndrome. This review focuses on the pathways involved in the normal accommodation reflex, the relevance of impaired gastric accommodation as a cause of morbidity and the methods used to assess gastric accommodation in humans. The available medical and therapeutic strategies based on the actual knowledge of the physiology and pharmacology of the accommodation reflex are outlined, with a focus on the role of nitrergic neurones and serotonergic receptors.

Effect of a proton pump inhibitor on postprandial gastric volume, emptying and symptoms in healthy human subjects: a pilot study

BACKGROUND

In consensus guidelines, proton pump inhibitors (PPIs) are recommended for the treatment of functional dyspepsia. It is unclear whether PPIs change gastric volume or emptying.

AIM

To assess the effect of a PPI, rabeprazole, on gastric volume and emptying and postprandial symptoms.

METHODS

In a double-blind, parallel-group placebo-controlled trial, 13 healthy participants were randomized to rabeprazole, 20 mg b.d., or placebo. On day 3, fasting gastric volume was measured using intravenous (99m)Tc-pertechnate and single photon emission computed tomography (SPECT). After the last dose of study medication, an (111)In-chloride egg meal (300 kcal) was ingested, and postprandial gastric volume and emptying were measured by SPECT. Symptom ratings using a visual analogue scale (fullness, nausea, bloating, abdominal pain, aggregate score) were obtained at baseline and 15, 30, 45, 60 and 75 min postprandially. Group comparisons were performed using Mann-Whitney rank sum test.

RESULTS

There were no statistically significant differences in gastric volume or emptying in the two groups. However, there was a borderline increase in gastric volume with rabeprazole compared with placebo. Rabeprazole treatment reduced aggregate postprandial symptoms, particularly fullness, 30 min after the meal (P = 0.01).

CONCLUSIONS

In healthy participants, rabeprazole, 20 mg b.d., did not significantly change gastric emptying, but reduced symptoms and had a borderline effect on gastric volume postprandially. The mechanism of reduced postprandial symptoms with a PPI requires further study.

New imaging in neurogastroenterology: an overview

Advances in imaging are being introduced initially as research tools and subsequently as clinical diagnostic tests. These investigations include modifications of the standard gastric emptying by scintigraphy to include application of intraluminal ultrasound to image sustained contractions and longitudinal shortening in the oesophagus, 2- and 4-h images, volumetric measurements to measure gastric volume, magnetic resonance (MR) imaging to appraise the structure and function of the rectal evacuation process, and brain imaging as a surrogate for the investigation of the brain's contribution to functional gastrointestinal disorders and chronic pain syndromes. There is a need for rigorous validation and measurement of the performance characteristics of these tests. Given the impact of gastric emptying at 4 h and single photon emission computerized tomography (SPECT) imaging for measuring gastric volumes on research and clinical practice, it is anticipated that, once validated, these different techniques are likely to have a significant impact on neurogastroenterology and, potentially, replace more invasive procedures.

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.

Gastric accommodation assessed by ultrasonography

Gastric accommodation is important for the under-standing of the pathophysiology in functional dyspepsia and is also relevant for symptom generation in other disorders. The term gastric accommodation has at least three different meanings: The accommodation process, the accommodation reflex, and the accommodation response. The gastric accommodation process is a complex phenomenon that describes how the size of the gastric compartment changes in response to a meal. The electronic barostat is considered the gold standard in assessing gastric accommodation. Imaging methods, including MRI, SPECT, and ultrasonography may also be used, particularly in patients who are stress-responsive, e.g. functional dyspepsia patients, as a non-invasive and less stress-inducing method is favourable. Ultrasonography satisfies these criteria as it does not by itself distort the physiological response in stress-responsive individuals.

Relationship of gastric emptying and volume changes after a solid meal in humans

Noninvasive imaging has been developed to measure gastric volumes. The relationship between gastric emptying and volume postprandially is unclear. The aims were to 1) develop a 3-dimensional (3D) single photon emission-computed tomography (SPECT) method to simultaneously measure gastric volume and emptying postprandially, 2) describe the course of gastric volume change during emptying of the meal, and 3) assess a 3D method measuring gastric emptying. In 30 healthy volunteers, we used (111)In-planar and (99m)Tc-SPECT imaging to estimate gastric emptying and volume after a radiolabeled meal. A customized analysis program of SPECT imaging assessed gastric emptying. A Bland-Altman plot assessed the performance of the new SPECT analysis compared with planar analysis. Gastric volume postprandially exceeds the fasting volume plus meal volume. The course of volume change and gastric emptying differ over time. Higher differences in volumes exist relative to fasting plus residual meal volumes at 15 min (median 763 vs. 568 ml, respectively, P < 0.001), 1 h (median 632 vs. 524 ml, P < 0.001), and 2 h (median 518 vs. 428 ml, P < 0.02), in contrast to similar volumes at 3 h (median 320 vs. 314 ml, P = 0.85). Analysis of SPECT imaging accurately measures gastric emptying compared with planar imaging with median differences of 1% (IQR -2.25 to 2.0) at 1 h, 1% (-3.25 to 2.25) at 2 h, and -2.5% (-4 to 0) at 3 h. Gastric volume exceeds meal volume during the first 2 postprandial hours, and simultaneous measurements of gastric volume and emptying can be achieved with a novel 3D SPECT method.

Does the nutrient drink test accurately predict postprandial gastric volume in health and community dyspepsia?

Nutrient drink tests have been proposed as a surrogate for measurement of gastric accommodation. To study the relationship of maximum tolerated volume (MTV) during nutrient drink test and gastric volumes measured by single-photon emission computed tomography (SPECT) in healthy controls and functional dyspepsia (FD) patients. We reviewed data from 85 healthy controls and 35 FD residents of south-eastern Minnesota. All underwent standardized nutrient drink and SPECT studies between August 2000 and June 2003. To test for associations between nutrient drink test and SPECT gastric volumes, we used multiple linear regression and partial regression analyses, assigning age, gender, dyspepsia status and postprandial symptoms as covariates in the model. In the combined group (healthy and FD), MTV was weakly associated with fasting gastric volume (r = 0.43, P = 0.0001) and with volume response to feeding (r = 0.25, P = 0.006). In the FD group, associations were similar (fasting r = 0.53, P = 0.001; postmeal r = 0.32, P = 0.06). After accounting for covariates, MTV only explained 13 and 3% of variations in fasting and postprandial volumes measured by SPECT. MTV during the nutrient drink test does not accurately reflect gastric volume measurements by SPECT in healthy controls and a sample of people in the community with FD.

Proximal gastric dysfunction in functional dyspepsia: Management options

Functional dyspepsia is a heterogeneous disorder where distinct pathophysiological abnormalities are present in subgroups of patients. Accommodation of the proximal stomach to a meal is impaired in up to half of the patients with functional dyspepsia. This is associated with symptoms of early satiety and weight loss. Drug interventions aimed at restoring impaired accommodation are currently being studied.