Barostat involves the placement of a polyethylene balloon into the stomach and linking it to a barostatic device to measure intragastric volumes in the fasting and postprandial periods⁵⁾. The barostat and intragastric polyethylene balloon provide an excellent method to study viscus tone and visceral hypersensitivity.

However, tube replacement itself is invasive in nature and can cause discomfort to patients, thereby limiting its role to research laboratory. Moreover, the barostat-controlled balloon cannot accurately measure posprandial accommodation of the entire stomach and the intragastric balloon itself may interfere with the intragastric handling of the meal¹⁶⁾.

Ultrasound studies of the proximal stomach allow non-invasive monitoring of meal induced relaxation of the proximal stomach¹⁷⁾. The experience about utrasound has been largely substantiated by Gilja et al.^17–20) Recently, three-dimensional ultrasound is being developed to measure proximal gastric volume¹⁹⁾, even though it is not yet widely available and requires further validation. However, the disadvantages of ultrasound are that it seems labor-intensive, requires a skilled sonographer and is likely to be observer-dependent.

This method was developed by Michael Camilleri et al. at Mayo Clinic²⁰⁾. This approach uses intravenous (i.v.) injection of a radioisotope, ^99mTc-pertechnetate with SPECT imaging of gastric mucosa, followed by image processing and analysis using a software.

Troncon et al.³⁰⁾ used a radioisotope to evaluate the shape of the stomach and identified differences in intragastric distribution of a meal, suggesting that the fundus fails to accommodate postprandially in patients with functional dyspepsia. Jan Tack and his colleagues performed a barostat study and reported that impaired gastric accommodation to a meal was found in 40% of patients with functional dyspepsia⁸⁾. The impaired gastric accommodation was associated with early satiety and weight loss. Kim et al.³⁵⁾ applied the SPECT study to assess gastric accommodation in patients with idiopathic nonulcer dyspepsia and healthy subjects and to evaluate the application of three-dimensional (tomographic acquisition) SPECT in a tertiary referral center at Mayo Clinic. All patients also had gastric emptying study by gastric scintigraphy. Among healthy subjects (8M, 12F), the postprandial/fasting gastric volume ratio was 4.9 1.7 (mean SD, 5th through 95th percentiles 38, median 4.6). 13/32 (41%) patients with idiopathic nonulcer dyspepsia had reduced postprandial accommodation (the ratio <3) (Figure 2). Gastric emptying was fast in four (13%), normal in 25 (78%) and slow in three (9%) patients. Both tests were normal in 50% of patients. Weight loss of >10 pounds tended to be more frequently observed in those with reduced accommodation (62% vs 32%, p=0.09). The study illustrated that the impaired gastric accommodation is more common than delayed gastric emptying in dyspeptic patients in a tertiary clinical setting.

Obesity, defined by an excess of body fat, is a highly prevalent disorder in the Western world³⁶⁾. Intragastric balloon studies showed that the gastric capacity was significantly larger^37–39) and the gastric capacity decreased after a restrictive diet in obese subjects³⁴⁾. However, inserting a gastric balloon or tube into the stomach and measuring the maximum water-filled balloon volume may reflect only an indirect index of gastric capacity. Furthermore, intubation itself may have evoked reflex relaxation of the stomach¹⁶⁾ or obese individuals may have had a more pronounced reflex relaxation in response to intubation, an artificial stimulus. Thus, Kim et al.⁴⁰⁾ applied SPECT method and satiety test to compare gastric accommodation and satiety between 13 obese (BMI 30 kg/m², mean BMI:37.0 kg/m²) and 19 non-obese (BMI < 30 kg/m², mean BMI: 26.2 kg/m²) asymptomatic subjects to prove the hypothesis that obese people had increased gastric accommodation and reduced postprandial satiety. The satiety test measured maximum tolerable volume of ingestion of liquid nutrient meal (Ensure) and symptoms 30 minutes after cessation of ingestion. The results have shown that fasting and postprandial gastric volumes and the ratio of postprandial/fasting gastric volume were not different between asymptomatic obese subjects and control subjects. Maximum tolerable volume of ingested Ensure and aggregate symptom score 30 min later were also not different between obese and control subjects. Therefore, asymptomatic obese people did not show either increased gastric accommodation or reduced satiety and those data suggested that gastric physiology is unlikely to provide an important contribution to development of moderate obesity.

After Nissen or laparoscopic fundoplication, patients frequently report upper abdominal (dyspeptic) symtoms. Theoretically, these symptoms may be the result of changes in function of the proximal stomach induced by fundoplication¹¹⁾. Smaller proximal stomach can be successfully documented by SPECT imaging in post-fundoplication patients³⁵, ⁴¹⁾ (Figure 2) and Samsom et al.⁴²⁾ reported that 2/4 post-fundoplication patients had total gastric volumes below those of healthy controls and could successfully documented. Kim et al.⁴¹⁾ also have shown by SPECT that 2/3 post-fundoplication patients had impaired gastric accommodation (the postprandial/fasting gastric volume ratio< 3). These studies are in agreement with barostat studies and therefore, SPECT study may be potentially, clinically applicable in patients who complain of dyspeptic symptoms after fundoplication.