Gastrointestinal Sounds and Migrating Motor Complex in Fasted Humans Takeshi Tomomasa, M.D., Akihiro Morikawa, M.D., Richard H. Sandler, M.D., Hussein A. Mansy, M.D., Hiroaki Koneko, M.D., Tabata Masahiko, M.D., Paul E. Hyman, M.D., and Zen Itoh, M.D. Department of Pediatrics and Institute for Molecular and Cellular Regulation, Gunma University School of Medicine, Maebashi, Japan; Rush Medical Center, Chicago, Illinois; and Children’s Hospital of Orange County, Orange, California Objective: We investigated the relationships among gastrointestinal sounds, gastrointestinal manometric findings, and small intestinal transit time in healthy fasted humans. Methods: Gastrointestinal sounds ac- quired with two microphones attached to the upper and lower abdominal walls of healthy subjects were quanti- fied with a computer-aided sound analysis program. Antroduodenal contractions were recorded by manom- etry. Small intestinal transit time was measured by breath hydrogen testing after intraduodenal administra- tion of lactulose. Results: The sum of the gastrointestinal sound amplitudes (sound index) in both the upper and lower abdomen changed with time, coinciding with the gastric phases of the migrating motor complex. The sound indices in the upper and lower abdomen were 59.0  24.8 and 98.1  21.6 mV/min in phase 1, 95.5  27.9 and 127.4  34.9 mV/min in phase 2, and 132.8  12.4 and 188.5  73.4 mV/min in phase 3, respectively. There were no significant differences among motility phases in terms of the mean duration or frequency of each sound event. Intravenous erythromycin induced phase 3 in the stomach and doubled the sound index. Somatostatin analogue induced phase-3–like clustered contractions in the duodenum, but inhibited antral con- tractions and decreased the sound index. The small in- testinal transit time was shorter and the sound index increased after intravenous metoclopramide, compared with controls. Scopolamine delayed small intestinal tran- sit time and decreased the sound index. Conclusions: This study is the first to document the relationships between gastrointestinal sounds and the migrating mo- tor complex. The chronological relation between antral motility and gastrointestinal sounds, and the dissimilar effects of erythromycin and somatostatin, suggest that antral contractions increase gastrointestinal sounds, perhaps by supplying gas into the intestine. (Am J Gas- troenterol 1999;94:374 –381. © 1999 by Am. Coll. of Gastroenterology) INTRODUCTION Gastrointestinal sounds, or bowel sounds, are a physical finding that can be monitored easily, painlessly, and at low cost. They have been used clinically as an indicator of bowel motility on certain occasions, especially for bedside diag- nosis of paralytic ileus. Nevertheless, gastrointestinal sounds have not been a topic of intensive scientific research until recently, because of great fluctuation with time and the lack of objective quantification (1, 2). Due to recent computer and software advances, it is now practical to collect and analyze large amounts of sound data (3–10). It has been shown that gastrointestinal sounds are decreased in patients with disorders causing mechanical obstructions (5) and with paralytic ileus due to acute appen- dicitis (5, 7). Carbachol increased gastrointestinal sounds (8) and atropine and oxybutynin decreased them (9) in healthy subjects. Recently, Campbell et al. (10) developed a system to analyze what they termed abdominal surface vibration by efficiently eliminating background noises. They reported that alternating hyperactivity and quiescence in the surface vibration corresponded with intestinal motility patterns and was diagnostic in patients with partial mechan- ical obstruction (11). However, the physiology associated with gastrointestinal sounds is still largely unknown. Be- cause gastrointestinal motility changes cyclically with time, understanding gastrointestinal sounds requires their corre- lation with gastrointestinal motility patterns. Fasting gastrointestinal motility is characterized by the repeated appearance of three distinctive phases, called the migrating motor complex (MMC), with an average cycle of 80 to 150 min (12, 13). The phase of repetitive propagating contractions called phase 3 is followed by a period of no contractions called phase 1. Phase 2, a phase of intermittent, variable-amplitude contractions, comes after phase 1, and is followed by phase 3. In the present study, we acquired gastrointestinal sounds from upper and lower abdominal surfaces continuously in healthy fasting subjects and corre- lated these sounds with phases of the interdigestive cycle of the proximal gastrointestinal tract. We also measured both gastrointestinal sounds and the small intestinal transit time Received May 20, 1998; accepted Oct. 5, 1998. THE AMERICAN JOURNAL OF GASTROENTEROLOGY Vol. 94, No. 2, 1999 Copyright © 1999 by Am. Coll. of Gastroenterology ISSN 0002-9270/99/$20.00 Published by Elsevier Science Inc. PII S0002-9270(98)00743-6 374