The effect of gastric secretion on gastric physiology and emptying in the fasted and fed state assessed by magnetic resonance imaging O. GOETZE,* R. TREIER,  M. FOX,*, à A. STEINGOETTER,  ,§ M. FRIED,*, à P. BOESIGER , à & W. SCHWIZER*, à *Division of Gastroenterology, University Hospital Zurich, Zurich, Switzerland  Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland àZurich Centre for Integrative Human Physiology (ZIHP), Zurich University, Zurich, Switzerland §Department of Nuclear Medicine, Technical University Munich, Munich, Germany Abstract Conventional measurement of gastric secretion is invasive and cannot assess the intra- gastric distribution of gastric contents or the effects of secretion on gastric function. This study assessed the effect of gastric secretion on gastric volume responses and emptying (GE) using a validated fast T 1 mapping magnetic resonance imaging (MRI) technique. Twelve healthy participants were studied in the fasted state and after 200 kcal Gadolinium-DOTA labelled glucose meal during intravenous infusion of penta- gastrin or placebo in double-blind, randomized order. Total gastric volume (TGV) and gastric content vol- ume (GCV) was assessed by MRI volume scans and secretion by fast T 1 mapping. Data was described by the j-coefficient (volume change after meal ingestion), by GE half time (T 50 ) and maximal GE rate (GER max ) derived all from a GE model. Pentagastrin increased GCV and TGV compared to placebo [j(GCV):1.6 ± 0.1 vs 0.6 ± 0.1; j(TGV): 1.6 ± 0.1 vs 0.7 ± 0.1; P < 0.001]. T 1 maps revealed a secretion layer above the meal, the volume of which was associated with j (R 2 = 83%, P < 0.001). TGV and GCV change were similar in both conditions (j; P = ns). T 50 was higher for pentagastrin than for placebo (84 ± 7 vs 56 ± 4min, P < 0.001); however, GER max was similar (5.9 ± 0.6 vs 4.9 ± 0.4 mL min )1 , P = ns). This study shows volume and distribution of gastric secretion can be quanti- fied in-vivo by non-invasive MRI T 1 mapping. Increased GCV drove TGV accommodation without evidence of a direct effect of pentagastrin or excess acid on gastric function. Secretion increases GCV thus prolongs GE as assessed by T 50 ; however, GE rate is unchanged. Keywords gastric emptying, gastric physiology, gastric secretion, magnetic resonance imaging, T 1 mapping. INTRODUCTION Gastric secretion is of key importance for the peptic digestion of food and has a role in regulating the rate of gastric emptying (GE) and the delivery of nutrients to the small bowel. In addition, gastric secretion has a role in the pathogenesis of common gastrointestinal diseases including peptic ulcer and gastroesophageal reflux disease (GERD). 1 The focus of previous investi- gations has been on hydrogen ion concentration (pH) in the gastrointestinal tract; however, (i) pH alone does not reflect the absolute ÔamountÕ of acid produced by the stomach or present in the refluxate, (ii) gastric secretion contains other potentially harmful chemicals (e.g. pepsin, trypsin and bile acid) and (iii) volume reflux with oesophageal distension is a common cause of ongoing symptoms in GERD patients that fail to respond to acid suppression with proton pump inhibi- tors (PPIs). 2,3 The important contribution of gastric secretion to postprandial intra-gastric volume is demonstrated by reports that up to 800 mL of gastric juice can be produced in response to a 400 mL solid Address for correspondence Oliver Goetze, MD, Division of Gastroenterology and Hepatology, University Hospital Zurich, Raemistr. 100, CH-8091 Zurich, Switzerland. Tel: +41 44 255 9229; fax: +41 44 255 4503; e-mail: oliver.goetze@usz.ch Parts of this work were presented at the DDW 2007, Washington, DC and at the Joint International Meeting for Neurogastroenterology and Motility 2008 in Luzern, Switzerland. Received: 15 October 2008 Accepted for publication: 4 February 2009 Neurogastroenterol Motil (2009) 21, 725–e42 doi: 10.1111/j.1365-2982.2009.01293.x Ó 2009 Blackwell Publishing Ltd 725