SPECT imaging of the stomach: comparison with barostat, and effects of sex, age, body mass index, and fundoplication. Single photon emission computed tomography

Functional dyspepsia

PURPOSE OF REVIEW

Functional dyspepsia is a common disorder, most of the time of unknown etiology and with variable pathophysiology. Therapy has been and still is largely empirical. Data from recent studies provide new clues for targeted therapy based on knowledge of etiology and pathophysiologic mechanisms.

RECENT FINDINGS

The role of Helicobacter pylori gastritis in the pathogenesis of functional dyspepsia has been defined: It is causative in a small minority of patients. Associations between (groups of) symptoms and pathophysiologic mechanisms have been established, but there is much overlap and interaction, and their relevance for the individual patient is uncertain, especially because of the variability of symptoms over time. Little progress has been made in pharmacotherapy of functional dyspepsia, but exploratory studies show interesting new options. Hypnotherapy seems a promising alternative.

SUMMARY

For the time being, diagnostic strategies for patients with suspected functional dyspepsia continue to be directed at excluding other disorders, in particular peptic ulcer disease and gastroesophageal reflux disease. In the presence of reflux symptoms, acid inhibitory therapy, preferably with a proton pump inhibitor, is a rational choice; otherwise, therapy is still empirical. Hypnotherapy is an option that could be seriously considered.

Relationship between partial gastric volumes and dyspeptic symptoms in fundoplication patients: a 3D ultrasonographic study

OBJECTIVES

Impaired gastric accommodation may induce dyspeptic symptoms in postfundoplication patients. Our aim was to assess the effect of a meal on total and partial gastric volumes in relation to dyspeptic symptoms in both dyspeptic and nondyspeptic fundoplication patients using three-dimensional (3D) ultrasonography.

METHODS

Eighteen postfundoplication patients of whom eight with and ten without dyspeptic symptoms and eighteen controls were studied. Three-dimensional ultrasonographic images of the stomach were acquired and symptoms were scored while fasting and at 5, 15, 30, 45, and 60 min after ingesting of a 500-ml liquid meal. From the 3D ultrasonographic images of the stomach the total, proximal, and distal gastric volumes were computed.

RESULTS

Dyspeptic and nondyspeptic fundoplication patients exhibited similar total gastric volumes at 5 min postprandially compared to controls, whereas smaller total gastric volumes were observed from 15 to 60 min postprandially (p = 0.007 and p < 0.001, respectively). Postprandial proximal/total gastric volume ratios were markedly reduced in both dyspeptic (0.39 +/- 0.016; p < 0.05) and nondyspeptic (0.38 +/- 0.016; p < 0.01) fundoplication patients compared to controls (0.47 +/- 0.008). In contrast, distal/total gastric volume ratios were larger in dyspeptic fundoplication patients (0.14 +/- 0.008) compared to both nondyspeptic fundoplication patients (0.11 +/- 0.007); p < 0.05) and controls (0.07 +/- 0.003); p < 0.001). Dyspeptic fundoplication patients had a higher postprandial score for fullness, nausea, and pain than nondyspeptic patients (p < 0.05) and controls (p < 0.05). Meal-induced distal gastric volume increase correlated significantly with the increase in fullness (r = 0.68; p < 0.01).

CONCLUSIONS

After a liquid meal, fundoplication patients exhibit a larger volume of the distal stomach compared with controls. Distal stomach volume was more pronounced in dyspeptic fundoplication patients and related with the increase in postprandial fullness sensations.

Comparison of gastric volumes in response to isocaloric liquid and mixed meals in humans

AIMS

To compare gastric volume responses to ingestion of isocaloric liquid or mixed (solid-liquid) meals and document the intra- and interindividual reproducibility of gastric volume measurement using single photon emission computed tomography (SPECT) imaging after i.v. 99mTc-pertechnetate.

METHODS

Eight healthy volunteers performed two studies at least 9 months apart. Gastric volumes were measured after a 317 kcal liquid nutrient meal. Within 2 weeks of the second liquid meal study, participants performed a third study, ingesting an isocaloric mixed meal. The order of the mixed and second liquid meals was randomized; Bland-Altman plot displayed data on repeated studies with liquid meal and paired t-test compared gastric volumes after mixed or liquid isocaloric meals.

RESULTS

Fasting and postprandial gastric volumes associated with the two liquid meals were not significantly different; inter- and intra-individual coefficients of variation were 13 and 13.8%. In response to the mixed meal, there was a lower absolute postprandial volume and lower change in gastric volume over fasting volume compared with the response to the liquid meal (P = 0.0001).

CONCLUSION

The SPECT measurement of gastric volumes in response to a nutrient liquid meal is reproducible. The magnitude of the volume response is greater after the liquid meal compared with the isocaloric mixed meal.

Effect of oral CCK-1 agonist GI181771X on fasting and postprandial gastric functions in healthy volunteers

CCK influences satiation and gastric and gallbladder emptying. GI181771X is a novel oral CCK-1 agonist; its effects on gastric emptying of solids, accommodation, and postprandial symptoms are unclear. Effects of four dose levels of the oral CCK-1 agonist GI181771X and placebo on gastric functions and postprandial symptoms were compared in 61 healthy men and women in a randomized, gender-stratified, double-blind, double-dummy placebo-controlled, parallel group study. Effects of 0.1, 0.5, and 1.5 mg of oral solution and a 5.0-mg tablet of GI181771X on gastric emptying of solids by scintigraphy, gastric volume by (99m)Tc-single photon emission computed tomographic imaging, maximum tolerated volume of Ensure, and postprandial nausea, bloating, fullness, and pain were studied. On each of 3 study days, participants received their randomly assigned treatment. Adverse effects and safety were monitored. There were overall group effects of GI181771X on gastric emptying (P < 0.01) and fasting and postprandial volumes (P = 0.036 and 0.015, respectively). The 1.5-mg oral solution of GI181771X significantly delayed gastric emptying of solids (P < 0.01) and increased fasting (P = 0.035) gastric volumes without altering postprandial (P = 0.056) gastric volumes or postprandial symptoms relative to placebo. The effect of the 5.0-mg tablet on gastric emptying of solids did not reach significance (P = 0.052). Pharmacokinetic profiles showed the highest area under the curve over 4 h for the 1.5-mg solution and a similar area under the curve for the 0.5-mg solution and 5-mg tablet. Adverse effects were predominantly gastrointestinal and occurred in a minority of participants. GI181771X delays gastric emptying of solids and exhibits an acceptable safety profile in healthy participants. CCK-1 receptors can be modulated to increase fasting gastric volume.

Functional dyspepsia: drugs for new (and old) therapeutic targets

The therapeutic management of functional dyspepsia remains a major challenge for the gastroenterologist. Current therapies available are based on putative underlying pathophysiologic mechanisms, including gastric acid sensitivity, slow gastric emptying and Helicobacter pylori infection, but only a small proportion of patients achieve symptomatic benefit from these therapeutic approaches. Relatively novel mechanistic concepts under testing include impaired gastric accomodation, visceral hypersensitivity, and central nervous system dysfunction. Serotonergic modulators (e.g. the 5-HT4 agonist tegaserod, the 5-HT3 antagonist alosetron and the 5-HT1P agonist sumatriptan), CCK-1 antagonists (e.g. dexloxiglumide), opioid agonists (e.g. asimadoline), N-methyl-D-aspartate (NMDA) receptor antagonists (e.g dextromethorphan), neurokinin antagonists (e.g. talnetant), capsaicin-like agents and antidepressants are among the agents currently under investigation. It seems unlikely, however, that targeting a single mechanism with an individual drug will result in complete symptom remission in most cases.

Assessment of gastric accommodation: overview and evaluation of current methods

Gastric accommodation is considered important in the pathophysiology of several upper gastrointestinal disorders including functional dyspepsia. The gold standard for its measurement is the barostat-balloon study which requires intubation. The aim was explore the reliability and performance characteristics of the techniques proposed for measurement of gastric accommodation. We undertook a literature search using MEDLINE with a broad range of key words. The accommodation reflex and its control are briefly described, based on human data. The performance characteristics of the intragastric barostat, transabdominal ultrasound, magnetic resonance imaging, single photon emission computed tomography, and satiation drinking tests are described. For each technique, we summarize the following: principle, validation studies, advantages, disadvantages, and potential applications. Three-dimensional methods to measure gastric volume non-invasively are promising and among the best validated to date. Simpler techniques would be of considerable appeal for clinical and research studies, but further validation is necessary before satiation drinking tests can be used as surrogates for more sophisticated measurements of gastric accommodation.

Treating irritable bowel syndrome: overview, perspective and future therapies

This article summarizes the ongoing challenges in irritable bowel syndrome and the exciting opportunities for development of novel therapies for this common, enigmatic condition. The challenges include insufficient understanding of mechanisms, lack of specificity of symptoms, differentiation from other conditions, and lack of availability of noninvasive tests to identify dysfunctions. However, significant opportunities are reflected by the advances in clinical trial design and, particularly, clinically relevant end points for such trials, and the increasing understanding of basic neuroenteric science. The latter has delivered two new medications to the practice (alosetron and tegaserod), and other candidate therapies (other serotonergic, tachykininergic, opioid, cannabinoid modulators) are being carefully appraised as potential drugs for the future.

Independent influences of body mass and gastric volumes on satiation in humans

BACKGROUND & AIMS

We assessed the association of body mass and gastric volumes (fasting and postprandial) with satiation and postprandial symptoms.

METHODS

Healthy obese and nonobese subjects underwent measurement of caloric intake at maximum satiation; postprandial symptoms were measured with visual analogue scales 30 minutes after a meal. Gastric volume during fasting and after 300 mL of Ensure was measured with technetium-99m single-photon emission computed tomography imaging. We used multiple regression analysis to assess the associations among variables.

RESULTS

Among 134 participants (81 women and 53 men), the median age was 26 years (range, 12-58 years), and the median body mass index was 24 kg/m(2) (range, 17-48 kg/m(2)). Increased body mass index, but not height, was associated with delayed satiation (P < 0.003, adjusted for sex). Overweight and obese subjects ingested, on average, 225 +/- 57 more kilocalories (945 +/- 239 kJ) at maximum satiation compared with normal weight individuals. Increased fasting gastric volume was not associated with body mass index or height, but it was significantly associated with delayed satiation (P = 0.001, adjusted for body mass index and sex). An increase of 50 mL in the fasting gastric volume was associated with 114 +/- 32 kcal (479 +/- 134 kJ) more ingested at maximum satiation. Increased body mass index was associated with lower fullness scores 30 minutes after a meal (P = 0.0012, adjusted for sex and volume of Ensure ingested). In contrast, scores of postprandial bloating and pain were higher with increased body mass index (both P < 0.05, adjusted for sex and volume of Ensure ingested).

CONCLUSIONS

Greater body mass index and fasting gastric volume are associated with reduced satiation. Increased body mass index or height was not associated with greater gastric volumes.

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

BACKGROUND

Recently, single photon emission computed tomography (SPECT) scanning was described as a non-invasive technique to assess fundic accommodation. However, in contrast with the barostat, no intragastric distending force is applied during SPECT scanning. We hypothesised that in the absence of a barostat balloon, SPECT scanning largely detects the volume effect of the ingested meal and is a rather insensitive tool to detect fundic relaxation.

METHODS

After an overnight fast, healthy volunteers underwent a barostat study and SPECT scanning on two separate days to assess: (1) meal induced fundic accommodation (Nutridrink, 200 ml, 300 kcal); and (2) gastric relaxation to 1 mg intravenous glucagon.

RESULTS

Fasting fundic volumes (145 (8) v 280 (32) ml; p=0.001) and average postprandial volume (329 (10) v 571 (53) ml; p=0.001) were significantly lower measured with SPECT compared with the barostat study. Meal induced fundic relaxation (183 (10) v 289 (46) ml; p=0.050) and the postprandial/fasting volume ratio (2.32 (0.10) v 2.27 (0.29); p=0.892) did not differ significantly between SPECT scanning and the barostat. However, no correlation could be determined between accommodation volumes measured by both techniques. In contrast with meal induced relaxation, the glucagon induced increase in fundic volume (19 (5) v 406 (56) ml; p=0.007) and post/pre glucagon ratio (1.16 (0.03) v 3.02 (0.54); p=0.046) were significantly lower when measured by SPECT scanning compared with the barostat.

CONCLUSION

SPECT scanning detects changes in postprandial volume but is less suitable than the gastric barostat in detecting changes in gastric tone. Our study therefore questions its role as a tool to detect impaired accommodation and warrants further validation of this technique.

Effect of a somatostatin analogue on gastric motor and sensory functions in healthy humans

BACKGROUND

Pharmacological approaches to alter satiation may have an impact on functional upper gastrointestinal disorders and potentially change food intake in obesity.

AIM

Our aim was to compare the effects of two doses of octreotide and placebo on postprandial symptoms, gastric accommodation, and gastric emptying using validated non-invasive techniques.

METHODS

In a randomised, parallel group, two dose, double blind, placebo controlled study, 39 healthy participants (13 per group) were randomised to 30 or 100 micro g octreotide or placebo, administered subcutaneously, 30 minutes before each study. Studies were performed on three separate days and included scintigraphic gastric emptying of solids and liquids, (99m)Tc SPECT imaging to measure fasting stomach volume and gastric accommodation following a 300 ml Ensure meal, and a standardised nutrient drink test to measure maximum tolerated volume and postprandial symptoms.

RESULTS

Relative to placebo, both doses of octreotide delayed gastric emptying of solids (not liquids), increased fasting gastric volume, reduced the change in gastric volume post meal, and decreased the sensation of fullness after a satiating meal.

CONCLUSION

The somatostatin analogue octreotide significantly alters human gastric functions, including inhibition of the normal reflex responses of gastric volume increase and emptying of the meal. These pharmacological effects suggest studies of the medication in disorders of satiation, including obesity and dyspepsia, are warranted.

Effects of asimadoline, a kappa-opioid agonist, on satiation and postprandial symptoms in health

AIM

To evaluate the effect of single administrations of asimadoline, a kappa-opioid agonist, on satiation volume, postprandial symptoms and gastric volumes.

METHODS

Healthy subjects received oral placebo, or 0.5 or 1.5 mg asimadoline in a randomized, double-blind fashion 1 h prior to testing. We assessed effects on the volume of Ensure to achieve full satiation and postprandial symptoms 30 min after meal, and on gastric volume (fasting and postprandial) measured by 99mTc-single photon emission tomography (SPECT) imaging.

RESULTS

Thirteen healthy subjects were studied in each treatment arm. Compared to placebo, asimadoline 0.5 mg decreased postprandial fullness (P = 0.027) without affecting the volume ingested at full satiation (P = 0.6). Asimadoline 1.5 mg decreased satiation during meal, allowing increased satiation volumes (P = 0.008) and tended to decrease postprandial fullness (P = 0.067), despite higher volumes ingested. There was a significant treatment-gender interaction in the effect of asimadoline on gastric volumes (P < 0.05). Asimadoline 0.5 mg (not 1.5 mg) increased fasting (P = 0.047) and postprandial (P = 0.009) gastric volumes in females but decreased fasting volumes in males (P = 0.008). The effect of asimadoline on gastric volume did not explain the effect observed on satiation volume (P = 0.371) or postprandial fullness (P = 0.399).

CONCLUSION

A single oral administration of asimadoline decreases satiation and postprandial fullness in humans independently of its effects on gastric volume.

Effects of glucagon-like peptide-1 and feeding on gastric volumes in diabetes mellitus with cardio-vagal dysfunction

Glucagon-like peptide-1 (GLP-1) increases gastric volume in humans possibly through the vagus nerve. Gastric volume response to feeding is preserved after vagal denervation in animals. We evaluated gastric volume responses to GLP-1 and placebo in seven diabetic patients with vagal neuropathy in a crossover study. We also compared gastric volume response to feeding in diabetes with that in healthy controls. We measured gastric volume using SPECT imaging. Data are median (interquartile range). In diabetic patients, GLP-1 did not increase gastric volume during fasting [5 mL (-3; 30)] relative to placebo [4 mL (-14; 50) P = 0.5], or postprandially [Delta postprandial minus fasting volume 469 mL (383; 563) with GLP-1 and 452 mL (400; 493) with placebo P = 0.3]. Change in gastric volume over fasting in diabetic patients on placebo was comparable to that of healthy controls [452 mL (400; 493)], P = 0.5. In contrast to effects in health, GLP-1 did not increase gastric volume in diabetics with vagal neuropathy, suggesting GLP-1's effects on stomach volume are vagally mediated. Normal gastric volume response to feeding in diabetics with vagal neuropathy suggests that other mechanisms compensate for vagal denervation.

Gastric accommodation and emptying in evaluation of patients with upper gastrointestinal symptoms

BACKGROUND & AIMS

Endoscopy-negative dyspepsia is a common symptom that often is difficult to define in pathophysiologic terms. The aim of this study was to assess the frequency of disordered gastric accommodation and emptying in patients referred with unexplained upper gastrointestinal symptoms.

METHODS

A computerized diagnostic index was used to identify all patients, 18-70 years old, who underwent single-photon emission computed tomography (SPECT) to assess gastric accommodation at Mayo Clinic Rochester over a 3-year period. Demographics, clinical features, and results of diagnostic testing, including scintigraphic gastric emptying, were extracted from the electronic record.

RESULTS

A total of 214 patients were identified; the primary clinical diagnoses were functional dyspepsia, postfundoplication syndromes, rumination syndrome, and diabetic dyspepsia. Gastric accommodation was impaired in 43% of the whole group: 47% of functional dyspepsia, 44% of postfundoplication syndromes, and 33% of diabetic dyspepsia. Delayed gastric emptying was most prevalent in diabetic dyspepsia, and was accelerated in postfundoplication syndromes groups. Thirty-seven percent of patients had abnormal gastric emptying. The highest prevalence of delayed gastric emptying was in the diabetic dyspepsia and accelerated gastric emptying in postfundoplication syndromes groups. Twenty-five percent of patients with normal gastric emptying had impaired accommodation. Upper-gastrointestinal symptoms were not different in groups based on gastric accommodation or emptying results.

CONCLUSIONS

Impaired gastric accommodation is common in patients with unexplained dyspepsia. Symptoms alone cannot predict physiologic disturbances. These noninvasive tests identify single or combined pathophysiologic disturbances and may help to identify subgroups of patients as candidates for more selective pharmacotherapy in the future.