Non-invasive topographic analysis of intestinal activity in man on the basis of acustic phenomena

In an attempt to find a non-invasive method yielding a comprehensive insight into a patient's intestinal activity, continuous multichannel registration and analysis of acustic phenomena as produced by the intestines were performed. Previous work, described by others, was further developed with respect to topographical interpretation of the data obtained, and to the possible introduction into general clinical use by installing different methods of artifact detection and reduction. To record and process bowel sounds, a device developed for this purpose (Phonoenteroanalyzer PEA-06, G-W Elektronik, Munich, FRG) was used. Five specially designed microphones were placed on the abdominal wall. After amplification and filtering, further processing of the signal was achieved by means of rectifying, peak detection, and logarithmic transformation techniques, yielding a topographically discernible pattern of intestinal activity. Noise and movement artifacts, although a basic problem of this technique, could be adequately managed, e.g., by using a control microphone as well as simultaneous registration of breathing. Ten normal subjects as well as eight patients with manifest or suspected gastrointestinal problems, had their bowel sounds registered either continuously overnight or during adequate stimulatory tests (gastrocolonic response, neostigmine test, rectal distension). Bowel sounds were registrated as short "clicks" or longer lasting, sometimes rhythmically appearing, complex acustic phenomena. Overnight registrations revealed periodical changes in general or local intestinal activity, which in turn showed remarkable interindividual variabilities. Stimulatory tests provoked an enhancement of intestinal activity, which could well be documented with this method. In conclusion, analysis of acustic phenomena provoked by the bowels should henceforth allow an objective, continuous, long-term, non-invasive, indirect, and at any time repeatable topographical registration of intestinal activity.