Mechanosensory properties in the human gastric antrum evaluated using B-mode ultrasonography during volume-controlled antral distension

Abstract

Mechanosensory properties in the human gastric antrum evaluated using B-mode ultrasonography during volume-controlled antral distension. Am J Physiol Gastrointest Liver Physiol 290: G876 -G882, 2006. First published November 17, 2005 doi:10.1152/ajpgi.00131.2005.-The aims of this study were to evaluate gastric antral mechanical behavior and distension-induced sensorimotor responses in the human gastric antrum using transabdominal ultrasound scanning. Ten healthy volunteers underwent volume-controlled ramp inflation of a bag located in the antrum with volumes up to 125 ml. The active and passive circumferential tensions and stresses were calculated from measurements of pressure, diameter, and wall thickness before and during the administration of the anticholinergic drug butylscopolamine. The bag distensions elicited contractions in the antrum and sensory responses below the pain threshold. Butylscopolamine abolished the contractions and significantly reduced the sensory response. The lengthtension diagram known from in vitro studies of smooth muscle strips could be reproduced as tension-volume diagrams in the human gastric antrum. The number of induced contractions and the contraction pressure amplitude (afterload) showed a parabolic behavior as function of the distension volume (preload), with maximum approximately at 70 ml. At the sensation threshold, the luminal circumference showed the lowest variation coefficient (13-25%), whereas the variation coefficient was more than 100% for the pressure, tensions, and stresses. We conclude that the muscle length-tension diagram and typical preload-afterload curves ad modem the Frank-Starling cardiac law can be obtained in the human gastric antrum. The sensory responses were most closely associated with the luminal circumference, indicating that the sensation during antral distension depends on deformation rather than on tension.biomechanics; preload; afterload; stress; strain; ultrasound THE GASTRIC ANTRUM PRIMARILY has a mechanical function, propelling contents received from the corpus of the stomach through the pylorus into the proximal part of the small intestine. Methods traditionally used for basic and clinical evaluation of the antrum are endoscopy, manometry, and radiographic examinations (4,(22)(23)(24). Manometry provides data on the contractile properties of the antrum but fails to provide data on the mechanical properties in general. During recent years, transabdominal ultrasound has aroused interest for use in the study of gastrointestinal physiology and for clinical evaluation of the stomach because it is a noninvasive and safe method applicable to the study of antral motility in patients with functional dyspepsia (2, 19). Transabdominal ultrasound provides geometric data; however, for analyses of tissue forces and stresses, it needs to be combined with manometry. Only a few studies have combined ultrasonography and manometry for the purpose of characterizing antral contractility (21). Furthermore, a limited number of studies have used ultrasonography to ...

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