Short Communication
Bowel Sounds: Is it Time for Surgeons to Hang-up their Stethoscopes?
Osama Elhardello1 and John Macfie1,2*
1Department of General Surgery, Scarborough General Hospital, UK
2The Combined Gastroenterology Research Unit, Scarborough General Hospital, UK
*Corresponding author: John Macfie, Department of General Surgery, University of Hull, York NHS FT, Scarborough Hospital, YO12 6QL, UK
Published: 17 Oct, 2018
Cite this article as: Elhardello O, Macfie J. Bowel Sounds:
Is it Time for Surgeons to Hang-up their
Stethoscopes?. World J Surg Surgical
Res. 2018; 1: 1066.
Short Communication
The noises produced by the movement of gas and fluids during peristalsis are bowel sounds
or borborygmi. We all have them to a greater or lesser extent. When the bowel is obstructed they
become high pitched or tinkling as fluid drips from one distended and tympanic loop of bowel into
another. In the presence of peritonitis, classically in association with a perforation, the abdomen
becomes silent reflecting an absence of peristaltic activity, so called paralytic ileus. Not surprisingly,
therefore, auscultation for bowel sounds is considered an essential part of the assessment of the
acute abdomen and it remains common practice to listen to bowel sounds as a determinant of
the presence or absence of gut function. But what is the evidence? Is listening to bowel sounds an
outdated practice now superseded by readily available abdominal imaging or is they still a useful
clinical observation which is easily obtained with minimal discomfort to the patient.
Cannon (1905) wrote the first systematic account of abdominal auscultation in relation to the
structure and function of the stomach and intestines [1]`. Since then many authors have attempted
to relate the properties of a bowel sound, or series of sounds, to precise structural conditions and
functional events within the alimentary tract. Advances in technology have allowed various systems
to be developed for the objective analysis of bowel sounds. Spectral analysis of bowel sounds was
first described by Horn et al. [2] in 1966. Yoshino et al. in 1990 attempted a computer analysis
of bowel sounds in intestinal obstruction [3]. They concluded that computer analysis of bowel
sounds of mechanical obstruction could provide a very objective assessment of severity, and could
help determine the treatment regimen (conservative or operative) of each patient. This was not
confirmed by a more recent study reported by Ching and Tang using an electronic stethoscope [4].
They found no correlation between bowel calibre and bowel sound characteristics in both acute
small bowel obstruction and acute large bowel obstruction concluding that auscultation of bowel
sounds is nonspecific for diagnosing bowel obstruction.
The intrinsic difficulty with the study of bowel sounds is that it is never possible to hear or
record exactly the same pattern of bowel sounds with exactly same amplitude, frequency, duration
and interval repeatedly and consistently as compared to the consistent sounds produced from the
heart, which has a set rhythm and sound characteristics over time. The bowel sounds heard from
the same patient will also differ at different times when the patient is re-examined. Not surprisingly
therefore the results of studies that have investigated observer variation have consistently found
poor results [5].
In 2014, Felder et al. [6], in a prospective study investigated the sensitivity, positive predictive
value and intra-rater reliability in a group of recordings from controls with normal gastrointestinal
function (n=177), patients with small bowel obstruction (n=19) and patients with post-operative
ileus (n=15). CT imaging was used as the gold standard reference point. A total of 10 recordings
from each group were replayed through speakers with 15 of them duplicated in order as to determine
the intra-rater reliability i.e. the ability of the listener to correctly recognize a duplicate recording.
Clinicians (n=41) were blinded and asked to indicate whether the sounds indicated normality, ileus
or obstruction. The overall sensitivity for normal, small bowel obstruction and post-operative ileus
was 32%, 22% and 22%. The positive predictive values for normal, small bowel obstruction and postoperative
ileus were 23%, 28% and 44%, respectively. The intra-rater reliability results for duplicated
sounds in normal subjects, small bowel obstruction patients and patients with post-operative ileus
were 59%, 52% and 53%. No statistically significant differences were found comparing clinicians
with a surgical to a medical background. They concluded that auscultating bowel sounds is not a
useful clinical practice and has poor differentiating ability between different bowel diseases.
Similar conclusions were drawn from the prospective study
reported by Breum et al. [7] in Denmark in 2015. In this study, 98
patients with suspected bowel obstruction were recruited and assessed
by 53 doctors. Bowel obstruction was confirmed by laparotomy or
endoscopy, and 37 patients were proven later to have obstruction. The
doctors were blinded for the outcome. Accuracy and inter-observer
agreement were generally low leading to their conclusion that clinical
decisions should not be based on assessment of bowel sounds.
The evidence would suggest therefore that auscultation of bowel
sounds is of limited value as a diagnostic discriminant on their
own. What then of the role of bowel sounds as a determinant of
gut function and, as a corollary to this are they a reliable aid to the
clinician in determining whether or not the patient has a paralytic
ileus. This was addressed in a prospective blind observational study
by Read et al. [8] in 2017. A total of 124 consecutive adult patients
who underwent major abdominal surgery were included. They
examined the association between the detection of bowel sounds and
evidence of GI function as evidenced by one of the following; passing
flatus, opening the bowels or tolerance of an oral intake. Tolerance of
oral diet was defined as intake of >1000 mls/24 hrs without vomiting.
The presence of bowel sounds was not associated with flatus passage,
bowel movement or tolerance of oral intake throughout the 10-day
study period. Bowel sounds had a low positive predictive value in
predicting flatus, bowel movement and tolerance of oral diet. They
concluded that bowel sounds are unreliable as a determinant of
whether ileus has resolved or not and is unreliable as a predictor of
tolerance of oral feeding in patients with post-operative ileus. Similar
conclusions were reached by van Bree and colleagues who reviewed
the literature on the clinical utility of listening to bowel sounds in
intensive care patients in 2018 [9]. Their search identified only 7 full
text publications and no Meta analyses or systematic reviews. They
concluded that auscultation with the aim of differentiating normal
from pathological bowel sounds is not useful in clinical practice and
that low values of inter and intra observer variability preclude the use
of bowel sounds for accurate clinical decision making.
In conclusion, listening to bowel sounds has limited utility as
an isolated clinical observation. In conjunction with other aspects
of abdominal examination they may serve to confirm or refute a
putative diagnosis of obstruction or ileus. They serve no purpose as a
means of assessing gut function. Nonetheless, it is not yet time for the
surgeon or surgical nurse to hang up their stethoscope. Auscultation
of the abdomen remains useful for a number of reasons: it ensures
close observation of the abdomen; silence may alert the clinician to
the possibility of ileus and symphonic tympany to obstruction. Most
importantly, perhaps, is that auscultation facilitates a period of calm
reflection in close proximity to the patient.
Authors Contributions
Osama Elhardello: Involved in carrying out the literature review,
drafting the manuscript, and in the final approval and submission for
publication.
John Macfie: Involved in drafting the manuscript, revising the
draft, final approval and the submission for publication.
References
- Cannon WB. Auscultation of the rhythmic sounds produced by the stomach and intestines. Am J Physiol. 1905;14(4):339-53.
- Horn G, Mynors J. Recording the bowel sounds. Med Biol Eng. 1966;4(2):205-8.
- Yoshino H, Abe Y, Yoshino T, Ohsato K. Clinical application of spectral analysis of bowel sounds in intestinal obstruction. Dis Colon Rectum. (1990);33(9):753-7.
- Ching SS, Tan YK. Spectral analysis of bowel sounds in intestinal obstruction using an electronic stethoscope. World J Gastroenterol. 2012;18(33):4585-92.
- Baid H. A critical review of auscultating bowel sounds. Br J Nurs. 2009;18(18):1125-9.
- Felder S, Margel D, Murrell Z, Fleshner P. Usefulness of bowel sound auscultation: A prospective evaluation. J Surg Educ. 2014;71(5):768-73.
- Breum BM, Rud B, Kirkegaard T, Nordentoft T. Accuracy of abdominal auscultation for bowel obstruction. World J Gastroenterol. 2015;21(34):10018-24.
- Read T, Brozovich M, Andujar J, Ricciardi R, Caushaj P. Bowel sounds are not associated with flatus, bowel movement, or Tolerance of Oral Intake in Patients after major abdominal surgery. Dis Colon Rectum. 2017;60(6):608-13.
- Van Bree SHW, Prins MMC, Juffermans NP. Auscultation for bowel sounds in patients with ileus: An outdated practice in the ICU? Neth J Crit Care. 2018;26(4):142-6.