Ultrasonography and three-dimensional methods of the upper gastrointestinal tract

Measurement of Gastrointestinal and Colonic Motor Functions in Humans and Animals

Accurately measuring the complex motor behaviors of the gastrointestinal tract has tremendous value for the understanding, diagnosis and treatment of digestive diseases. This review synthesizes the literature regarding current tests that are used in both humans and animals. There remains further opportunity to enhance such tests, especially when such tests are able to provide value in both the preclinical and the clinical settings.

Three-dimensional ultrasound imaging

This review is about the development of three-dimensional (3D) ultrasonic medical imaging, how it works, and where its future lies. It assumes knowledge of two-dimensional (2D) ultrasound, which is covered elsewhere in this issue. The three main ways in which 3D ultrasound may be acquired are described: the mechanically swept 3D probe, the 2D transducer array that can acquire intrinsically 3D data, and the freehand 3D ultrasound. This provides an appreciation of the constraints implicit in each of these approaches together with their strengths and weaknesses. Then some of the techniques that are used for processing the 3D data and the way this can lead to information of clinical value are discussed. A table is provided to show the range of clinical applications reported in the literature. Finally, the discussion relating to the technology and its clinical applications to explain why 3D ultrasound has been relatively slow to be adopted in routine clinics is drawn together and the issues that will govern its development in the future explored.

Feasibility and application of 3-dimensional ultrasound for measurement of gastric volumes in healthy adults and adolescents

OBJECTIVES

Abnormal gastric accommodation to a meal results in dyspepsia. Current methods to measure gastric volume (GV) are invasive or involve ionizing radiation. The aims of this study were to compare fasting and postprandial (PP) GVs measured by (99m)Tc-single photon emission computed tomography (SPECT) and 3-dimensional ultrasound (3D-US) in adults, to assess the performance characteristics of 3D-US measurement of GV during fasting and postprandially, and to develop normative data of GVs in 24 healthy adolescents.

PATIENTS AND METHODS

Eleven adults underwent SPECT and 3D-US simultaneously to measure GV, and a second 3D-US alone within 1 week of the first study. Twenty-four adolescents underwent 1 3D-US measurement. Each study included fasting, a 300-mL Ensure meal, and 0 to 30-minute PP GV measurements.

RESULTS

3D-US identifies GV accommodation to 300mL Ensure. Delta (0-30 minutes average PP fasting) GV was 444mL (median, interquartile range [IQR]=422, 534) for 3D-US and 543mL (median, IQR=486, 564) for SPECT (P=0.15). There were larger interindividual coefficients of variation for GV by 3D-US (60.3% fasting and 21.3% average PP) compared with 19% fasting and 9.2% PP for SPECT. Intraindividual coefficients of variation for the 2 3D-US measurements in adults were 84% fasting and 44% average PP. The estimated GVs for the adolescent group (median [25th-75th IQR]) were 33 (18-53)mL fasting, 330 (284-357)mL 30 minutes PP, and 281 (240-324)mL for delta GV.

CONCLUSIONS

3D-US is a promising method to measure GV accommodation to a meal. Large coefficients of variation reflect the learning stage in development of this promising technique.

Methods for measurement of gastric motility

There is an array of tests available to measure gastric motility. Some tests measure end points, such as gastric emptying, that result from several different functions, whereas other tests are more specific and test only a single parameter, such as contractility. This article reviews the tests most commonly available in practice and research to evaluate in vivo the gastric functions of emptying, accommodation, contractility, and myoelectrical activity. The rationale for testing, the relative strengths and weaknesses of each test, and technical details are summarized. We also briefly indicate the applications and validations of the tests for use in experimental animal studies.

Increased visceral sensitivity in Giardia-induced postinfectious irritable bowel syndrome and functional dyspepsia. Effect of the 5HT3-antagonist ondansetron

In an outbreak of waterborne giardiasis where 1300 subjects were diagnosed, with Giardia lamblia, 139 continued to have abdominal symptoms of whom two of three had negative stool culture and microscopy. These were considered to have a postinfectious functional gastrointestinal disorder. We investigated visceral hypersensitivity in patients with persisting abdominal symptoms after Giardia infection and assessed the effect of 5HT(3)-antagonist ondansetron. Twenty-two patients with Giardia negative stools and 19 controls were included. A subset of patients (n = 15) had both irritable bowel syndrome (IBS) and functional dyspepsia (FD). All subjects underwent a satiety test with a soup combined with three-dimensional ultrasound. Fifteen of 22 patients underwent double-blind, randomized, placebo-controlled study with the 5-HT(3) antagonist ondansetron given orally. Drinking capacity was lower in patients than in controls (P < 0.01) and gastric emptying was reduced (P < 0.05). Patients had more symptoms both fasting and postprandially (P < 0.001) compared to controls. Ondansetron had no effect on these parameters except from less nausea postprandially (P < 0.05). In conclusion, patients with Giardia-induced gastrointestinal symptoms developed both IBS and FD. They exhibited gastric hypersensitivity with lower drinking capacity and delayed gastric emptying. The 5-HT(3) antagonist ondansetron did not improve drinking capacity, gastric emptying or symptoms except nausea.

Measurements of gastric emptying of low- and high-nutrient liquids using 3D ultrasonography and scintigraphy in healthy subjects

Scintigraphy represents the 'gold standard' for the measurement of gastric emptying. Recent studies suggest that three-dimensional (3D) ultrasonography may allow a precise measure of gastric emptying, given the capacity for accurate volume calculations of the stomach. The aim of this study was to compare measurements of gastric emptying of both low- and high-nutrient drinks by 3D ultrasonography with scintigraphy. Ten healthy young subjects (6M, 4F, age 23.5 +/- 1.5 years) were studied on 2 days. Concurrent measurements of gastric emptying by scintigraphy and 3D ultrasonography were performed after ingestion of 500 mL beef soup (12 kcal) or 300 ml dextrose (25% w/v) (314 kcal) labelled with 20 MBq (99m)Tc-sulphur colloid. There was no significant difference between scintigraphic and ultrasonographic 50% emptying times (T50s) (soup: 27.7 +/- 4.8 min vs 23.8. +/- 4.8 min; dextrose: 122.2 +/- 13.3 min vs 131.9 +/- 10.2 min). There was a close correlation between scintigraphic and ultrasonographic T50s for both soup (r = 0.92, P = 0.0005) and dextrose (r = 0.88, P = 0.0007). For the T50s, the limits of agreement were -15.2 min and +8.1 min for the soup (mean difference -3.6 min) and -35.3 min and +47.6 min for dextrose (mean difference +6.2 min). 3D ultrasonography provides a valid measure of gastric emptying of liquid meals in healthy subjects.

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.