Influence of a 5HT1 receptor agonist on gastric accommodation and initial transpyloric flow in healthy subjects

Sumatriptan, a 5HT1 receptor agonist, inhibits antral motor activity, delays gastric emptying and relaxes the gastric fundus. The aim of this study was to characterize the effect of sumatriptan on transpyloric flow and gastric accommodation during and immediately after ingestion of a liquid meal using duplex sonography. Ten healthy subjects were investigated twice on separate days. In random order either sumatriptan 6 mg (Imigran® 0.5 mL) or a placebo were given s.c. 15 min before ingesting 500 mL of a meat soup. The subjects were examined during the 3-min period before ingestion of the liquid meal, the 3-min spent drinking the meal and 10 min postprandially. Sumatriptan caused a significant widening of both the gastric antrum (P=0.02) and the proximal stomach (P=0.01) 10 min postprandially as compared with placebo. It caused no significant differences in time to initial gastric emptying (P=0.2), but significantly delayed commencement of peristaltic-related transpyloric flow (P=0.04). Sumatriptan had no significant effect on mean abdominal symptom scores, but after sumatriptan there was a significant negative correlation between width of postprandial antral area and postprandial nausea and between width of postprandial antral area and postprandial bloating. We therefore conclude that sumatriptan causes a postprandial dilatation of both the distal and the proximal stomach with no change in dyspeptic symptoms nor in length of time to first gastric emptying. Time to commencement of peristaltic-related emptying is delayed.     

Gastric emptying of a non-digestible solid: assessment with simultaneous SmartPill pH and pressure capsule, antroduodenal manometry, gastric emptying scintigraphy

Abstract  Gastric emptying of digestible solids occurs after trituration of food particles. Non-digestible solids are thought to empty with phase III of the migrating motor complex (MMC). The aim of this study was to determine if a non-digestible capsule given with a meal empties from the stomach with return of the fasting phase III MMC or during the fed pattern with the solid meal. Fifteen normal subjects underwent antroduodenal manometry and ingestion of a radiolabelled meal and SmartPill wireless pH and pressure capsule. In five subjects, emptying of the SmartPill was studied in the fasting period by ingesting the SmartPill with radiolabelled water. The SmartPill emptied from the stomach within 6 h in 14 of 15 subjects. SmartPill pressure recordings showed high amplitude phasic contractions prior to emptying. SmartPill gastric residence time (261 ± 22 min) correlated strongly with time to the first phase III MMC (239 ± 23 min; r  = 0.813; P  < 0.01) and correlated moderately with solid-phase gastric emptying ( r  = 0.606 with T-50% and r  = 0.565 with T-90%). Nine of 14 subjects emptied the capsule with a phase III MMC. In five subjects, the SmartPill emptied with isolated distal antral contractions. In five subjects ingesting only water, SmartPill gastric residence time (92 ± 44 min) correlated with the time to the first phase III MMC (87 ± 30 min; r  = 0.979; P  < 0.01). The non-digestible SmartPill given with a meal primarily empties from the stomach with the return of phase III MMCs occurring after emptying the solid-phase meal. However, in some subjects, the SmartPill emptied with isolated antral contractions, an unappreciated mechanism for emptying of a non-digestible solid.     

Role of vagal innervation on intragastric distribution and emptying of liquid and semisolid meals in conscious pigs

The role of vagal innervation on emptying patterns and intragastric distributions of liquid and semisolid meals is still controversial. We aimed to record these features after dorsal, ventral and truncal vagotomies, using external gamma scintigraphy in conscious pigs in which the dorsal vagus specifically innervates the proximal stomach. Imaging of the stomach was performed for all experimental situations and before surgery using 99mTc-labelled glucose and porridge meals. Emptying of liquids was faster after dorsal vagotomy, whereas it was unchanged after ventral and truncal vagotomies (T1/2 = 57 +/- 8.5, 31 +/- 14.4, 54 +/- 9.1 and 42 +/- 14.9 min for intact, dorsal, ventral and truncal vagotomies, respectively). On the other hand, truncal vagotomy significantly reduced the emptying rate of semisolids whereas dorsal and ventral vagotomies had no significant effect (T1/2 = 96 +/- 7.2, 113 +/- 8.1, 75 +/- 9.9 and 260 +/- 56.6 min for intact, dorsal, ventral and truncal vagotomies). Morphological analysis of the gastric shape confirmed an overdistended proximal stomach after truncal vagotomy only. For semisolids, proximal stomach emptying followed the same emptying pattern as the entire stomach, irrespective of the surgical procedure. We concluded that the proximal stomach is the main control for the emptying of liquids and semisolids. The vagal control of overall gastric emptying for semisolids is probably identical to that modulating the intragastric distribution of the meal.     

Gastric emptying: the validity of the paracetamol absorption test adjusted for individual pharmacokinetics

An algorithm for the paracetamol absorption test for gastric emptying, adjusting for individual pharmacokinetics, was recently developed. The aim of the present study was to validate the use of this algorithm. Furthermore, the algorithm was applied to elucidate whether a gastric tube interferes with the rate of gastric emptying. A caloric liquid meal with paracetamol was administered orally to nine healthy volunteers on two separate days. On one occasion, the subjects were intubated with a nasogastric tube and the meal was aspirated from the stomach 45 min after meal intake. The percentage of the meal retained in the stomach at the time of aspiration was determined by analyses of paracetamol in the aspirate and compared with calculations by the algorithm. On the other examination day, the same meal was ingested without tube and aspiration. The median percentage of the meal retained in the stomach at aspiration was 47% (range 33-70%) calculated by the algorithm and 48% (range 23-61%) based on the aspiration data. The correlation between the emptying parameters was r=0.97 (P < 0.001). The median of gastric emptying parameters was similar when the number of samples included in the calculation by the algorithm was reduced, but the range tended to increase. The gastric tube moderately inhibited gastric emptying during the period 20-40 min after meal intake (P < 0.05), but for the period from meal intake until start of aspiration, no inhibition was found. The present study demonstrates that the novel algorithm for the paracetamol absorption test provides valid estimates for gastric emptying.     

Regional gastric emptying abnormalities in functional dyspepsia and gastro-oesophageal reflux disease

To characterize proximal and distal stomach emptying in functional dyspepsia (FD) and gastro-oesophageal reflux disease (GORD). Eighty-three patients underwent gastric emptying (GE) scintigraphy and symptom scoring for the evaluation of upper gastrointestinal symptoms and were divided into three groups: FD (n = 25), GORD (n = 20) and FD + GORD (n = 38). Total, proximal and distal gastric retention were determined scintigraphically and compared with normal controls. Delayed total GE was observed in each subgroup: FD (56%), GORD (45%) and FD + GORD (55%). Greater proximal gastric retention was observed after meal ingestion in GORD compared to FD. Greater distal gastric retention was observed in FD and FD + GORD but it was only mild in GORD. Nausea, vomiting, early satiety, distention and regurgitation were associated with proximal gastric retention whereas there was no symptom associated with distal gastric retention. Multiple regression demonstrated total gastric retention at 30 min and 1 h was positively correlated with regurgitation whereas early proximal gastric retention was positively correlated with regurgitation and negatively correlated with nausea. Selective abnormalities of proximal and distal stomach emptying were demonstrated in GORD and FD. GORD and FD symptoms were associated with proximal gastric retention suggesting that proximal stomach motor function may be important in the pathogenesis of symptoms associated with these disorders.     

Intragastric distribution of a standardized meal in health and functional dyspepsia: correlation with specific symptoms

In functional dyspepsia, abnormal intragastric distribution of a test meal has been identified but has never been correlated to any symptom pattern. The aim of this study was to compare the intragastric distribution of a meal between functional dyspepsia patients and controls, and to correlate distribution with symptom patterns, using scintigraphic gastric emptying studies. In forty patients with functional dyspepsia and 29 healthy volunteers, scintigraphic planar images were obtained immediately after ingestion of a mixed radiolabelled test meal and every 20 min for 2 h. The images of the stomach were divided into proximal and distal compartments. The mean intragastric distribution was similar in patients and controls. Over the whole test, 18 (45%) and 20 (50%) patients had a distal redistribution of the solid and liquid phase of the meal, respectively, while proximal retention of these phases was found in 13 (33%) and 9 (23%) patients. Early satiety was associated with early distal redistribution of the liquid phase and fullness was associated with late proximal retention. This study shows similar intragastric distribution of a test meal in health and functional dyspepsia. Within the patient group, an association between abnormal intragastric distribution patterns and symptom profiles was found, which might be related to different pathophysiological mechanisms.     

Effect of lateral positioning on gastroesophageal reflux (GER) and underlying mechanisms in GER disease (GERD) patients and healthy controls

Background Posture has been shown to influence the number of transient lower esophageal sphincter relaxation (TLESRs) and gastroesophageal reflux (GER), however, the physiology explaining the influence of right lateral position (RLP), and left lateral position (LLP) is not clear. The aim of this study was to determine the influence of RLP and LLP on TLESRs and GERD after a meal in GER disease (GERD) patients and healthy controls (HC) while monitoring gastric distension and emptying. Methods Ten GERD patients and 10 HC were studied for 90 min (30 min test meal infusion, 30 min postprandial in either RLP or LLP (randomly assigned) and 30 min in alternate position). The study was repeated on a separate day in reverse position order. TLESRs, GER, and gastric emptying rate were recorded using manometry, multichannel intraluminal impedance, and ¹³C‐octanoate breath tests. Gastric distension was visualized by five serial gastric volume scintigraphy scans during the first 30 min. Key Results Gastroesophageal reflux, (GER) disease patients had increased numbers of TLESRs in RLP compared to LLP in the first postprandial hour [5 (4–14) and 4.5 (2–6), respectively, P = 0.046] whereas the number of TLESRs was not different in RLP and LLP [4 (2–4) and 4 (3–6), respectively, P = 0.7] in HC. Numbers of GER increased similar to TLESRs in GERD patients. In GERD patients, gastric emptying reached peak ¹³CO₂ excretion faster and proximal gastric distension was more pronounced. Conclusions & Inferences In GERD patients, TLESRs, GER, distension of proximal stomach, and gastric emptying are increased in RLP compared to LLP. This effect is not seen in HC.     

Effects of gastric electrical field stimulation with long pulses on gastric emptying in dogs

The aim was to investigate the effects of electrical field stimulation (EFS) with long and short pulses on gastric emptying, gastric contractility and vagal activity in dogs. Sixteen dogs were equipped with a duodenal cannula, electrodes and strain gauges (10 dogs) in the stomach. Each dog was fed with Ensure and gastric effluent was collected from the cannula. Electrical stimulation was applied via two electrodes (about 12 cm apart, one in the corpus and the other in the antrum) with long pulses (a frequency of 6 cycles min-1, pulse amplitude of 6 mA and width of 100 ms) in 10 dogs and with short pulses (frequency of 30 Hz and pulse width of 300 micros) in six dogs. The electrocardiogram was also recorded and heart rate variability was derived to assess the vagal activity. It was found that: (i). EFS with long pulses did not alter gastric emptying during stimulation but increased gastric emptying during the 45 min immediately after stimulation; (ii). EFS with long pulses increased gastric contractility in both proximal and distal antrum during and after the stimulation; (iii). EFS with long pulses resulted in an increase in vagal tone during the 45 min immediately after stimulation. However, there is no difference during the 45 min period of stimulation; (iv). EFS with short pulses had no effect on gastric emptying. We concluded that long pulse gastric electrical field stimulation with one electrode in the corpus and the other electrode in the antrum has postponed effects on gastric emptying of liquid, gastric contractility and vagal activity.     

Measuring the interaction of meal and gastric secretion: a combined quantitative magnetic resonance imaging and pharmacokinetic modeling approach

Background The stimulation and intragastric accumulation of gastric secretion has been recognized as an important factor in gastroesophageal reflux disease. However, the interaction of gastric secretion and meal emptying has not been fully understood. Current methods to assess gastric secretion are either invasive or unable to provide information on its volume, distribution and dynamics. The aim of this study was to quantify the interaction between meal emptying and meal induced gastric secretion by using quantitative magnetic resonance imaging (MRI) and pharmacokinetic analysis. Methods A chocolate test meal was developed which is secretion stimulating and MRI compatible. Meal emptying and gastric secretion were assessed in fourteen healthy volunteers using a validated quantitative MRI technique. A population based pharmacokinetic model was developed and applied to the extracted volume data, assessing the meal emptying rate, rate of secretion and their interaction. Key Results The test meal continuously induced gastric secretion in all subjects, which partly accumulated at the meal–air interface, forming a ‘secretion layer’ in the proximal stomach. Traditional fitting detected a significant correlation between meal emptying rate and rate of secretion. The pharmacokinetic model quantified this interaction and estimated a 2.3 ± 1 fold higher effect of meal on secretion than vice versa. The efficacy of the emptied meal to produce gastric secretion was 61%. Conclusions & Inferences The combined quantitative MRI and pharmacokinetic model approach allows for the quantification of gastric secretion volume and its interaction on meal emptying. The observed secretion layer might explain previous findings postulating the presence of an intragastric ‘acid pocket’.     

Influence of sumatriptan on gastric accommodation and on antral contraction in healthy subjects assessed by ultrasonography

Background Oral sumatriptan administration has been reported to delay gastric emptying after liquid meals. The aim of this study was to determine whether delayed gastric emptying is caused by enhanced gastric accommodation, impaired antral contractions, or both using ultrasonography. Methods Ten healthy volunteers were enrolled in this randomized two‐way crossover study. After overnight fasting, the subjects received the liquid meal 60 min after ingesting a 50 mg sumatriptan tablet with 50 mL of water or 50 mL of water alone (control). The cross‐sectional area of the proximal stomach was measured in a supine position after every 100 mL. The frequency and amplitude of the antral contractions were measured in a slightly backward sitting position. The intragastric distribution of the liquid meal was assessed by calculating the proximal stomach/distal stomach ratio (prox/distal ratio). Key Results The cross‐sectional area after drinking 100, 200, and 300 mL of the liquid meal (oral sumatriptan vs control) was 34.49 vs 15.11 cm² (P = 0.0051), 48.00 vs 30.61 cm² (P = 0.0166), and 58.67 vs 47.19 cm² (P = 0.0125), respectively. There was no significant difference in the amplitude of contractions, contraction cycle, motility index, and prox/distal ratio (97.15 vs 97.93%, P = 0.0745; 19.42 vs 19.5 s, P = 0.8590; and 887.58 vs 889.22, P = 0.5751; 9.75 vs 8.41, P = 0.8785; respectively). Conclusions & Inferences Oral sumatriptan administration enhanced gastric accommodation after the ingestion of liquid nutrients, but had no significant effect on antral contractions or intragastric distribution in healthy subjects.     

Effect of mianserin on gastric sensorimotor function and gastric emptying: a randomized,placebo‐controlled,double‐blind,crossover study in healthy volunteers

Background Antidepressants such as mianserin can improve symptoms in some functional dyspeptic patients but their mechanism of action remains unclear. We aimed to assess the effects of mianserin on gastric sensorimotor function in man. Methods In this randomized, placebo‐controlled, double‐blind, crossover study 12 healthy subjects (six men) underwent a gastric barostat study and a gastric emptying breath test after 7 days pretreatment with placebo or mianserin (20 mg; p.o.). Graded isobaric and isovolumetric distentions were performed to determine gastric compliance and sensitivity. Subsequently, intrabag pressure was held constant and the volume increase after administration of a liquid meal (200 mL; 300 kcal) was studied. Breath was sampled before and after ingestion of a test meal and half‐emptying times for solids and liquids were determined from the breath samples. Mianserin was compared to placebo using t‐tests and mixed model analysis (mean ± SD). Key Results Mianserin did not affect pressures or volumes needed to induce first perception or discomfort. During isovolumetric distensions compliance was decreased after mianserin treatment (1.8 ± 0.4 vs 2.0 ± 0.3 mmHg 100 mL^?1; P < 0.05). Premeal volumes were comparable in both treatment arms (221 ± 99 vs 220 ± 88 mL), but meal‐induced relaxation during the first 30 min was significantly inhibited after mianserin treatment (F_6,40 = 2.58, P < 0.05). Mianserin did not affect either solid or liquid gastric emptying. Conclusions & Inferences Mianserin does not alter gastric emptying rate or sensitivity to gastric distension, but inhibits gastric accommodation to a meal in its early phase. These observations provide no explanation for the effects of mianserin in functional dyspeptic patients.     

Effects of clonidine and sumatriptan on postprandial gastric volume response, antral contraction waves and emptying: an MRI study

Abstract Gastric emptying (GE) may be driven by tonic contraction of the stomach (‘pressure pump’) or antral contraction waves (ACW) (‘peristaltic pump’). The mechanism underlying GE was studied by contrasting the effects of clonidine (α₂‐adrenergic agonist) and sumatriptan (5‐HT₁ agonist) on gastric function. Magnetic resonance imaging provided non‐invasive assessment of gastric volume responses, ACW and GE in nine healthy volunteers. Investigations were performed in the right decubitus position after ingestion of 500 mL of 10% glucose (200 kcal) under placebo [0.9% NaCl intravenous (IV) and subcutaneous (SC)], clonidine [0.01 mg min^?1 IV, max 0.1 mg (placebo SC)] or sumatriptan [6 mg SC (placebo IV)]. Total gastric volume (TGV) and gastric content volume (GCV) were assessed every 5 min for 90 min, interspersed with dynamic scan sequences to measure ACW activity. During gastric filling, TGV increased with GCV indicating that meal volume dictates initial relaxation. Gastric contents volume continued to increase over the early postprandial period due to gastric secretion surpassing initial gastric emptying. Clonidine diminished this early increase in GCV, reduced gastric relaxation, decreased ACW frequency compared with placebo. Gastric emptying (GE) rate increased. Sumatriptan had no effect on initial GCV, but prolonged gastric relaxation and disrupted ACW activity. Gastric emptying was delayed. There was a negative correlation between gastric relaxation and GE rate (r² = 49%, P < 0.001), whereas the association between ACW frequency and GE rate was inconsistent and weak (r² = 15%, P = 0.05). These findings support the hypothesis that nutrient liquid emptying is primarily driven by the ‘pressure pump’ mechanism.     

Gastric emptying in normal subjects: reproducibility and relationship to characteristics of the migrating motor complex

This study was designed to clarify whether a part of the variability in gastric emptying could be ascribed to a relationship between meal ingestion and phase activity of the migrating motor complex and whether reproducibility is increased when meal ingestion takes place in relation to preselected characteristics of the migrating motor complex. We examined 12 healthy males, and the design included three examinations, twice with meal ingestion in a duodenal Phase I, and once in a Phase II. The meal consisted of an omelette labelled with ^99mTc followed by 150 ml water labelled with ¹¹¹In. The results showed that liquid lag phase (min) and was significantly shorter in Phase II than in Phase I (1 vs. 4, P = 0.007). The half emptying time of solid linear phase (min) was reproduced with nearly identical median and range values in the three series (I[1]: 67[51–87]; I[2]: 63[47–80]; 61[47–76]). With meal ingestion in Phase I a significant difference between inter- and intra-individual variance could not be demonstrated. With meal ingestion in Phase I a second examination in Phase I did not increase reproducibility of any of the variables compared to a second examination in Phase II. In conclusion, scientific investigations on gastric emptying have to be performed with phase related meal ingestion and a double-radionuclide technique.     

Involvement of NO in gastric emptying of semi-solid meal in conscious pigs

The influence of non-selective nitric oxide synthase (NOS) inhibition on gastric emptying of a semi-solid meal was studied in conscious pigs. Antroduodenal motility and fundic compliance were also assessed to evaluate the mechanisms at the origin of potential alteration in gastric emptying pattern. N(G)-nitro-L-arginine methyl ester (L-NAME; 20 mg kg(-1) i.v.) delayed gastric emptying (half-emptying time of 128.98 +/- 16.86 min vs 73.74 +/- 7.73 min after saline, P < 0.05, n = 6) as a result of decreased proximal gastric emptying. No changes were observed for distal gastric emptying as a result of unchanged antral motility. Similarly, no changes were noted on duodenal motor patterns either in the fasted or in the fed state. L-NAME decreased fundic compliance in fasted state (49 +/- 11 mL mmHg(-1) vs 118 +/- 15 mL mmHg(-1) after saline, P < 0.05, n = 6). As this phenomenon is expected to increase emptying rate, the gastroparesis induced by NOS inhibition is thus likely to originate from distal resistive forces. It is concluded that NO positively modulates gastric emptying.     

Postprandial proximal gastric acid pocket in patients after distal gastrectomy

Background An unbuffered postprandial proximal gastric acid pocket (PPGAP) has been noticed in the majority of normal individuals and patients with gastroesophageal reflux disease. The role of gastric anatomy, specifically the antrum, in the physiology of the PPGAP is not yet fully elucidated. This study aims to analyze the presence of PPGAP in patients submitted to distal gastrectomy. Methods A total of 15 patients who had a distal gastrectomy plus DII lymphadenectomy and Roux‐en‐Y reconstruction for gastric adenocarcinoma (mean age 64.3 ± 8.4 years, 12 females) were studied. All patients were free of foregut symptoms after the operation. Patients underwent a high‐resolution manometry. A station pull‐through pH monitoring was performed from 5 cm below the lower border of the lower esophageal sphincter (LBLES) to the LBLES in increments of 1 cm in a fasting state and 10 min after a standardized fatty meal. Postprandial proximal gastric acid pocket was defined by the presence of acid reading (pH<4) in a segment of the proximal stomach between non‐acid segments distally (food) and proximally (LBLES). The PPGAP extent was recorded. The protocol was approved by local ethics committee. Key Results Acidity was not detected in the stomach of nine patients before meal. After meal, PPGAP was not found in three patients. In three patients (20%), a PPGAP was noted with an extension of 1, 1 and 3 cm. Conclusions & Inferences In conclusion, PPGAP is present in a minority of patients after distal gastrectomy; this finding may suggest that the gastric antrum may play a role in the genesis of the PPGAP.     

Gastric secretion does not affect the reliability of the 13C‐acetate breath test: A validation of the 13C‐acetate breath test by magnetic resonance imaging

Background ¹³C‐Acetate labeled meals are widely used to determine meal emptying by means of analyzing resulting ¹³CO₂ exhalation dynamics. In contrast to the underlying metabolic processes, only few ¹³C breath test meal emptying studies have focused on intragastric processes that may alter ¹³CO₂ exhalation. This work assessed the effect of enhanced gastric secretion on the reliability of half emptying time (t50) measurements by ¹³C‐acetate breath test. Methods ¹³CO₂ exhalation data were acquired in a double‐blind, randomized, cross‐over gastric emptying study in 12 healthy volunteers receiving either pentagastrin or placebo intravenously. The standard method proposed by Ghoos et al. was applied to calculate t50 (t50_Ghoos) from ¹³CO₂ exhalation data, which were compared and tested for agreement to meal half emptying times (t50_MV) from concurrent recorded MRI (magnetic resonance imaging) volume data. In addition, the accumulated gastric secretion volumes during infusion as detected by MRI (AUC_SV₆₀) were correlated with the corresponding cumulative percent ¹³C doses recovered (cPDR₆₀). Key Results t50_Ghoos and t50_MV showed a linear correlation with a slope of 1.1 ± 0.3 (r² = 0.67), however, a positive offset of 136 min for t50_Ghoos. No correlation was detected between AUC_SV₆₀ and cPDR₆₀ (r² = 0.11). Both, breath test and MRI, revealed a prolonged t50 under pentagastrin infusion with median differences in t50_Ghoos of 45[28–84] min (P = 0.002) and t50_MV of 39[28–52] min (P = 0.002). Conclusions & Inferences This study suggests that ¹³CO₂ exhalation after ingestion of a ¹³C‐labeled liquid test meal is not affected by stimulated gastric secretion, but is rather reflecting the dynamics of meal or caloric emptying from the stomach.     

Effect of meal volume on gastric emptying

Abstract While the volume of a liquid meal has been identified as the principal accelerator of gastric emptying of liquids, the relationship between meal volume and gastric emptying of solids has been controversial. With solid foods, the need to reduce solid foods into small particles (trituration) before passage might obscure the effect of meal volume on solid propulsion. To distinguish trituration from driving force as the rate-limiting factor for emptying, 75 (1.6 mm) nylon spheres were fed along with different amounts of steak meals (150, 300 and 600 g), or alternatively, 50, 100 or 200 (1.6 mm) nylon spheres were fed to six dogs with 300 g steak meals. To examine the effect of meal volume on gastric emptying, we studied the effect of different meal volumes on the speed of gastric emptying of liquids (150, 300, 600 and 1200 ml of phosphate buffer) and solids (150, 300 and 600 g of cooked beef steak) in five dogs with duodenal fistulas. Intestinal inhibition was eliminated by diverting all chyme through the fistulas. In the absence of intestinal feedback, we found that gastric emptying of steak and spheres were different in that steak emptying was independent of meal volume (g min^-1 was constant across 150–600 g) while sphere emptying was affected by the number of spheres in the stomach and that liquid emptying was dependent on the meal volume (ml min^-1 increased across 150–1200 ml). Thus, meal volume accelerated gastric emptying provided the process is not rate-limited by trituration.     

Effect of Intraduodenal Infusion of Acid on the Antropyloroduodenal Motor Unit in Human Volunteers

Intraduodenal acid has been shown to delay gastric emptying. We have investigated the effect of infusing hydrochloric acid into the duodenum on the motor activity of the gastric antrum, pylorus, and duodenum in 18 healthy volunteers. Pressures in the gastric antrum, pylorus, and duodenum and the pH in the antrum and duodenum were recorded in response to alternate duodenal infusions of normal saline and 0.1 M isotonic hydrochloric acid at constant (1 or 2 ml/min) or increasing (1, 2, 3.75, and 5 ml/min) rates. Repetitive infusions of acid (1 or 2 ml/min) were associated with 1) a decrease in antral pressure waves (p < 0.05), 2) a reduction in coordinated pressure waves involving the duodenum (p < 0.05) and replacement by random contractile activity, and 3) an increase in isolated pyloric pressure waves (IPPWs) (p < 0.05). Increasing the rate of acid infusion reduced the rate of coordinated contractions involving the antrum (r = -0.39; p < 0.01) and increased the rate of IPPWs (r = 0.45; p < 0.01). There were significant correlations between the percentage of time that the duodenal pH was less than 2, and both the rate of coordinated contractions involving the antrum (r = -0.28; p < 0.01) and the rate of IPPWs (r = 0.34; p < 0.01). These changes in antropyloroduodenal motor activity may contribute to the delay in emptying of acidic solutions from the stomach.     

Inter‐observer reproducibility and analysis of gastric volume measurements and gastric emptying assessed with magnetic resonance imaging

Background Magnetic resonance (MR) imaging provides direct, non‐invasive measurements of gastric function and emptying. The inter‐observer variability (IOV) of MR volume measurements and the most appropriate analysis of MR data have not been established. To assess IOV of total gastric volume (TGV) and gastric content volume (GCV) measurements from MR images and the ability of standard power exponential (PowExp), and a novel linear exponential (LinExp) model to describe MR data. Methods Ten healthy volunteers received three different volumes of a liquid nutrient test meal (200–800 mL) on 3 days in a randomized order. Magnetic resonance scans were acquired using a 1.5T system every 1–5 min for 60 min. Total gastric volume and GCV were measured independently by three observers. Volume data were fitted by PowExp and LinExp models to assess postprandial volume change and gastric emptying half time (T₅₀). Key Results An initial rise in GCV and TGV was often observed after meal ingestion, thereafter GCV and TGV decreased in an approximately linear fashion. Inter‐observer variability decreased with greater volumes from 12% at 200 mL to 6% at 600 and 800 mL. Inter‐observer variability for T₅₀ was <5%. PowExp and LinExp models provided comparable estimates of T₅₀; however, only LinExp described dynamic volume change in the early postprandial period. Conclusions & Inferences Gastric MR provides quantitative measurements of postprandial volume change with low IOV, unless the stomach is nearly empty. The novel LinExp model describes the dynamic volume changes in the early postprandial period more accurately than the PowExp model used in existing gastric emptying studies.     

Cyclooxygenase-2 inhibition increases gastric tone and delays gastric emptying in rats.

We evaluated the effects of cyclooxygenase-2 (COX-2) selective inhibitors, COX-1 selective inhibitor, or COX non-selective inhibitor on gastric emptying and intestinal transit of liquids, and evaluated the effect of a COX-2 selective inhibitor on gastric tonus (GT). Male Wistar rats were treated per os with saline (control), rofecoxib, celecoxib, ketorolac, rofecoxib + ketorolac, celecoxib + ketorolac, or indomethacin. After 1 h, rats were gavage-fed (1.5 mL) with the test meal (5% glucose solution with 0.05 g mL(-1) phenol red) and killed 10, 20 or 30 min later. Gastric, proximal, medial or distal small intestine dye recovery (GDR and IDR, respectively) were measured by spectrophotometry. The animals of the other group were treated with i.v. valdecoxib or saline, and GT was continuously observed for 120 min using a pletismomether system. Compared with the control group, treatment with COX-2 inhibitors, alone or with ketocolac, as well as with indomethacin increased GDR (P < 0.05) at 10-, 20- or 30-min postprandial intervals. Ketorolac alone did not change the GDR, but increased the proximal IDR (P < 0.05) at 10 min, and decreased medial IDR (P < 0.05) at 10 and 20 min. Valdecoxib increased (P < 0.01) GT 60, 80 and 100 min after administration. In conclusion, COX-2 inhibition delayed the gastric emptying of liquids and increased GT in rats.