March 1st, 2017
Listening to Bowel Sounds: An Outdated Practice?
Medical programs teach us that listening to bowel sounds is an essential part of the physical examination of the abdomen, especially when the differential includes ileus, small bowel obstruction, diarrhea or constipation. Woe betide the student who fails to auscultate the abdomen of patients with these presentations. Yet firstly there’s little supporting evidence for this maneuver, and secondly there’s a lack of consensus about correct technique. Despite these issues, bowel sounds are claimed to help us develop our differential and cinch our diagnosis. The relationship between bowel sounds and pathology is not evidence based. It appears to be more a reflection of tradition and anecdotal evidence.
The noises produced by the movement of gas and fluids during peristalsis are bowel sounds. The technique learned depends on the school, the clinical gut of faculty and staff, and the physical exam text chosen. Some educators teach students that listening in one area is enough whereas others teach them to listen in all four quadrants. Bates’ recommends listening in only one spot, Mosby’s in all four quadrants, and DeGowin’s suggests listening in all four quadrants and the midline. Given that borborygmi may disseminate across the entire abdomen, and what you hear in one quadrant may reflect another part of the abdomen, the precise placement of your stethoscope seems irrelevant.
Also controversial is the duration of auscultation. Educators (and texts) teach students to listen for bowel sounds for anything from 30 seconds to 7 minutes. In reality, a healthy person may have no sounds for several minutes but then later have up to 30 a minute. Bowel sounds may cycle with peak-to-peak periods over 50-60 minutes. This means that any analysis less than that time will be inadequate.1 Additionally, some intestinal contractions are silent, so we cannot presume that a quiet bowel is a motionless bowel.
This complexity is further compounded by order of operations. Schools in the United States teach students to listen prior to palpation whereas schools elsewhere teach students to auscultate after palpation. I was taught to listen in each quadrant for up to 30 seconds or until bowel sounds were heard. This was done prior to palpation. Reversing the procedure was considered unacceptable. The thinking here is that palpation might disturb the intestines, trigger peristalsis, and thus alter the physical exam. My question is — so what?
There’s little evidence to suggest that borborygmi triggered by palpation are any more or less pathological than those that are not. I also suspect that patients might push on their own bellies before a clinician ever enters the room or even in their presence to illustrate their pain: it hurts here!
In researching this issue lately, as I folded page corners of great medical tomes and drew boxes around pertinent information, I felt that I might do just as well turning those pages into something tangible, relevant and concrete; something akin to the Japanese art of origami – a model of bird’s beak esophagus perhaps.
A friend and colleague of mine who trained as a surgeon in South Africa in the 1970’s described to me his memories of learning the nuances of borborygmi. Back then, this was their art.
“When I trained, and did a lot of intestinal surgery, borborygmi really meant being able to hear loud bowel sounds without a stethoscope. We learned to listen for those differences that depict ileus from mechanical intestinal obstruction, an important distinction since the mechanical obstruction often needed an urgent operation while ileus did not; we learned to distinguish propulsive sounds from ‘tinkling,’ non-propulsive ones. I got quite good at that as a chief registrar in Johannesburg. My teachers and the master clinicians who taught me, translated bowel sounds into action. Propulsion — operate! Tinkling — don’t operate!”
The most common and urgent reason to listen to bowel sounds is small bowel obstruction (SBO). The instruction is that bowel sounds will be hyperactive or absent in the setting of SBO. This is the time when the diligent clinician should wield their scope, placing the diaphragm below the diaphragm. However, in a recent study, 53 doctors used a Littman’s electronic stethoscope to assess the bowel sounds of patients with and without SBO. The median frequency with which doctors classified borborygmi as abnormal did not differ significantly between patients with and without bowel obstruction (26% vs. 23%, P=0.08). The study concluded that auscultation of the abdomen provided little help when making clinical decisions regarding management.2
A study published in The Journal of Surgical Education in 2010 came to similar conclusions. They found that “listeners frequently arrive at the incorrect diagnosis.” Listeners were unable to accurately characterise bowel sounds as normal, SBO or ileus. They also noted no difference in accuracy between surgical and internal medicine residents. They concluded that listening to bowel sounds is not a clinically useful part of the physical exam.3
Another reason to listen to bowel sounds is ileus. A study in 2012 examined the utility of listening to bowel sounds as a method of determining the end of post-operative ileus. This study determined that there was no association between the finding of bowel sounds and the return of bowel activity. This research concludes that routine assessment of bowel sounds for resolution of ileus is according to an outdated and unnecessary procedure.4 Undeniably, patients with ileus and SBO often do have abnormal bowel sounds, but it appears that listening for them has little utility in clinical practice today.
I am a keen supporter of the history and physical exam. I advocate for the use of hands, ears and eyes. However, clinicians must be progressive, embracing new modalities and letting go of less reliable methods. For example, teaching bedside ultrasound for the diagnosis of SBO might be a better use of time. A recent systematic review and meta-analysis of the diagnostic modalities used to identify SBO found ultrasound to be superior to all other modalities.5
It is unlikely that medical, nursing and physician assistant programs will stop teaching students to listen for borborygmi any time soon. I hope though that the lack of both evidence and standardisation will at least encourage students, educators and clinicians to question the efficacy and utility of this maneuver. No one should fault the clinicians of earlier times; they lacked the technology and data we have today. Some might consider auscultating for bowel sounds as another part of our arsenal for deployment, rather like Homans’s sign for deep vein thrombosis: something to pull out of our medical tool bag when diagnostic resources are scarce – when our scope is all we have. That said, given the lack of consensus and supporting evidence, I believe patients might benefit more from the ancient art of origami than borborygmi. At least the former might soothe the patient.
1) McGee, S, Evidence-Based Physical Diagnosis, 3rd Edition. Philadelphia, PA: Elsevier-Saunders; 2012
2) Breum BM, Rud B, Kirkegaard T, Nordentoft T. Accuracy of abdominal auscultation for bowel obstruction. World Journal of Gastroenterology : WJG. 2015;21(34):10018-10024. doi:10.3748/wjg.v21.i34.10018.
3) Felder S, Margel D, Murrell Z , Fleshner P. Usefulness of Bowel Sound Auscultation: A Prospective Evaluation. Journal of Surgical Education, 2014-09-01, Volume 71, Issue 5, Pages 768-773.
4) Massey R. Return of bowel sounds indicating an end of postoperative ileus: is it time to cease this long-standing nursing tradition? Medsurg Nursing, 2012-05, Volume 21, Issue 3, Page 146 -150
5) Taylor N, Lalani M. Adult Small Bowel Obstruction. Journal of the Society of Academic Emergency Medicine,5) 2013-06-12, Volume 20, Issue 6, Pages 527-544