The ultrasound meal accommodation test in 509 patients with functional gastrointestinal disorders

Aim: The Ultrasound Meal Accommodation Test (UMAT) is a clinical test used to assess gastric accommodation, gastric emptying, and visceral sensitivity. It has been used as a clinical tool at Haukeland University Hospital, Bergen for more than 20 years.

Material and methods: Five-hundred and nine patients were retrospectively evaluated, 71% females, and 51% were referred from other hospitals or specialists. The aim was to explore the usefulness of UMAT in patients with suspected functional GI disorders (FGID).

Results: One hundred and sixty patients were diagnosed with functional dyspepsia (FD), and 154 patients were diagnosed with irritable bowel syndrome (IBS). The overlap between IBS and FD was 41%. In 36% of FD patients, ultrasound assessment showed impaired gastric accommodation. Of 262 patients filling out all required fields for the FD diagnosis (ROMA II and III), 198 (74%) met the criteria for FD, but only 91 (34%) were later diagnosed with FD by an experienced clinician.

Conclusions: By combining ultrasonography, the symptom response to a standardized meal, and psychological assessment, the UMAT is useful in diagnosis and management of patients with FGID.     

A closed-loop human simulator for investigating the role of feedback control in brain-machine interfaces

Neural prosthetic systems seek to improve the lives of severely disabled people by decoding neural activity into useful behavioral commands. These systems and their decoding algorithms are typically developed "offline," using neural activity previously gathered from a healthy animal, and the decoded movement is then compared with the true movement that accompanied the recorded neural activity. However, this offline design and testing may neglect important features of a real prosthesis, most notably the critical role of feedback control, which enables the user to adjust neural activity while using the prosthesis. We hypothesize that understanding and optimally designing high-performance decoders require an experimental platform where humans are in closed-loop with the various candidate decode systems and algorithms. It remains unexplored the extent to which the subject can, for a particular decode system, algorithm, or parameter, engage feedback and other strategies to improve decode performance. Closed-loop testing may suggest different choices than offline analyses. Here we ask if a healthy human subject, using a closed-loop neural prosthesis driven by synthetic neural activity, can inform system design. We use this online prosthesis simulator (OPS) to optimize "online" decode performance based on a key parameter of a current state-of-the-art decode algorithm, the bin width of a Kalman filter. First, we show that offline and online analyses indeed suggest different parameter choices. Previous literature and our offline analyses agree that neural activity should be analyzed in bins of 100- to 300-ms width. OPS analysis, which incorporates feedback control, suggests that much shorter bin widths (25-50 ms) yield higher decode performance. Second, we confirm this surprising finding using a closed-loop rhesus monkey prosthetic system. These findings illustrate the type of discovery made possible by the OPS, and so we hypothesize that this novel testing approach will help in the design of prosthetic systems that will translate well to human patients.     

Pressure-induced gastric accommodation studied with a new distension paradigm. Abnormally low accommodation rate in patients with functional dyspepsia

OBJECTIVE: A new distension paradigm, by which the gastric volume response to ramp-tonic distension can be analysed in detail, has been developed. The aim of this study was to investigate the applicability of this new paradigm in man, and to compare pressure-induced gastric accommodation in healthy volunteers (HV) and patients with functional dyspepsia (FD). MATERIAL AND METHODS: Ten HV, and 11 FD patients were examined twice; once in the fasting state and once postprandially. Intragastric bag pressure was raised from 1 to 12 mmHg in 4 min (ramp phase) and then kept constant for 5 min (tonic phase). RESULTS: Compared to HV, fasting FD patients had lower gastric accommodation rates (0.9+/-0.2 versus 2.5+/-0.4 ml/s, p=0.002), lower maximum volume (239+/-39 versus 428+/-64 ml, p=0.01) and a longer accommodation time (157+/-26 versus 92+/-15 s, p=0.03). A test meal prior to distension tended to normalize the response in FD patients. CONCLUSIONS: This new barostat paradigm allowed detailed analysis of short-term pressure-induced accommodation in man. Impaired gastric distension-induced accommodation is a novel abnormality in FD.     

In vitro strain measurement in the porcine antrum using ultrasound doppler strain rate imaging

Strain rate imaging (SRI) enables study of deformation in soft tissues. The aim of this study was to evaluate the accuracy of SRI in measuring strain in the porcine antral wall in vitro. An experimental set-up enabled controlled distension of a porcine stomach in a saline reservoir. Radial strain obtained by SRI was compared with radial strain calculated from B-mode ultrasonography. Circumferential strain obtained by SRI was compared with circumferential strain calculated from sonomicrometry. The agreement between radial strain values measured by SRI and B-mode, along and across several ultrasound (US) beams, using US frequency 6.7 MHz and strain length (SL) = 1.9 mm was = -1.0 +/- 12.1% and 0.5 +/- 13.4%, respectively (mean difference +/- 2SD%) and it was better than with SL 1.2 mm. Compared with sonomicrometry, SRI-determined circumferential strain using 6.7 MHz and SL = 1.9 mm was less accurate, whether averaging along or across several US beams (-9.2 +/- 46.7% and 13.8 +/- 51.2%, respectively). In conclusion, SRI gave accurate measurement of radial strain of the antral wall, but seemed to be less accurate for measurement of circumferential strain for this in vitro set-up.     

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.     

Diagnostic Accuracy of Transabdominal Ultrasound in Chronic Pancreatitis

The performance of transabdominal ultrasound (US) in chronic pancreatitis (CP) following the advances in US technology made during recent decades has not been explored. Our aim in this prospective study was to evaluate the diagnostic accuracy of modern abdominal US compared with the Mayo score in CP. One hundred thirty-four patients referred for suspected CP were included in the study. Fifty-four patients were assigned the diagnosis CP. After inclusion, transabdominal US was performed. Ductal features (calculi, dilations and caliber variations, side-branch dilations and hyper-echoic duct wall margins) and parenchymal features (calcifications, cysts, hyper-echoic foci, stranding, lobulation and honeycombing) were recorded. Features were counted and scored according to a weighting system defined at the international consensus meeting in Rosemont, Illinois (Rosemont score). Diagnostic performance indices (95% confidence interval) of US were calculated: The unweighted count of features had a sensitivity of 0.69 (0.54–0.80) and specificity of 0.97 (0.90–1). The Rosemont score had a sensitivity of 0.81 (0.69–0.91) and specificity of 0.97 (0.90–1). Exocrine pancreatic failure was most pronounced in Rosemont groups I and II (p < 0.001). We conclude that using both unweighted and weighted scores, the diagnostic accuracy of modern transabdominal US is good. The extent of pancreatic changes detected by the method is correlated with exocrine pancreatic function.     

Monitoring postprandial size of the proximal stomach by ultrasonography.

The purpose of this study was to develop a sonographic method to monitor postprandial size of the proximal stomach. Twenty-three healthy persons were scanned in a sitting position with a 3.25 MHz transducer after ingestion of 500 ml meat soup. The area in a sagittal section and the maximal diameter in an oblique frontal section were chosen as standard measurements. The soup emptied from the proximal stomach in a linear manner (r = 0.99) and at a rate of 2.0 +/- 1.3%/min. Intraobserver error of the scans (mean +/- SD) was 5.6% +/- 2.3% and 9.5% +/- 4.5% for sagittal area and frontal diameter, respectively, and the corresponding interobserver error was 5.3% +/- 4.0% and 8.3% +/- 5.3%, respectively. This sonographic method demonstrated a moderate day-to-day variation, had low intra- and interobserver error, and allowed estimation of initial emptying fractions of the proximal stomach.