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Background: Although the auscultation of bowel sounds is considered an essential component of an adequate physical examination, its clinical value remains largely unstudied and subjective. The aim of this study was to determine whether an accurate diagnosis of mechanical small bowel obstruction, postoperative ileus, or normal controls is possible based on bowel sound characteristics.
Methods: Using an electronic stethoscope (3M Littmann Model 3200) with sound amplification capabilities and a computer Bluetooth interface, bowel sounds of healthy volunteers (n=10), patients with a CT diagnosed mechanical small bowel obstruction demonstrated by a transition point and confirmed at surgery (n=10), and patients with postoperative ileus (n=10) were recorded for 30 seconds while lying in the supine position. The bowel sounds were transferred into a computer and then replayed randomly through high definition speakers to study physicians blinded to the clinical scenario. A total of 45 recordings were played consecutively, with 15 of the recordings duplicated. A survey was taken just prior to the recording playback assessing each physician's perceived level of expertise interpreting bowel sounds. Study physicians were instructed to categorize the patient recording as normal, obstructed, ileus, or not sure.
Results: Study physicians (n=28) included 4 medical students on a surgical service, 8 surgical interns, 4 senior surgical residents, and 12 surgical attendings. Most participants (64%) stated they rarely listened to bowel sounds in their training or clinical practice. Almost all (96%) responded they knew what normal bowel sounds should sound like, but were less confident in what obstructive bowel sounds should sound like (71%). Study participants correctly diagnosed the clinical scenario in a median of 11 (range, 5-16) of the 45 recordings (23%). A median of 2 (range, 0-22) responses were ‘not sure.' Normal bowel sounds were correctly identified 29% of the time with a positive predictive value (PPV) of 22%. Obstructive bowel sounds were correctly identified 24% of the time with a PPV of 26%. Postoperative ileus was correctly identified 20% of the time with a PPV of 39%. No difference was found in diagnostic accuracy between levels of training. For participants responding he/she was ‘always able' to identify normal or obstructive bowel sounds if present, accuracy of diagnosis was 32% and 29%, respectively. Fixed-marginal inter-observer kappa value was only 0.17.
Conclusion: Auscultation of bowel sounds is not a useful clinical practice when trying to differentiate normal versus ileus versus obstruction. Based on our results, the listener usually arrives at an incorrect diagnosis, and the low inter-observer agreement further suggests the inaccuracy of utilizing bowel sounds for clinical purposes. Routinely listening to bowel sounds should be abandoned.