Accuracy of abdominal auscultation for bowel obstruction

Abstract

Aim: To investigate the accuracy and inter-observer variation of bowel sound assessment in patients with clinically suspected bowel obstruction.

Methods: Bowel sounds were recorded in patients with suspected bowel obstruction using a Littmann(®) Electronic Stethoscope. The recordings were processed to yield 25-s sound sequences in random order on PCs. Observers, recruited from doctors within the department, classified the sound sequences as either normal or pathological. The reference tests for bowel obstruction were intraoperative and endoscopic findings and clinical follow up. Sensitivity and specificity were calculated for each observer and compared between junior and senior doctors. Interobserver variation was measured using the Kappa statistic.

Results: Bowel sound sequences from 98 patients were assessed by 53 (33 junior and 20 senior) doctors. Laparotomy was performed in 47 patients, 35 of whom had bowel obstruction. Two patients underwent colorectal stenting due to large bowel obstruction. The median sensitivity and specificity was 0.42 (range: 0.19-0.64) and 0.78 (range: 0.35-0.98), respectively. There was no significant difference in accuracy between junior and senior doctors. The median frequency with which doctors classified bowel sounds as abnormal did not differ significantly between patients with and without bowel obstruction (26% vs 23%, P = 0.08). The 53 doctors made up 1378 unique pairs and the median Kappa value was 0.29 (range: -0.15-0.66).

Conclusion: Accuracy and inter-observer agreement was generally low. Clinical decisions in patients with possible bowel obstruction should not be based on auscultatory assessment of bowel sounds.

Keywords: Accuracy; Auscultation; Bowel obstruction; Bowel sounds; Diagnostic test; Multi-observer; Observer variation; Prospective.

Figure 1

Box plot showing distributions of the proportion of patients with pathological bowel sounds per doctor in 37 patients with bowel obstruction and 61 patients with no obstruction. Each doctor contributes one proportion to each column.

Figure 2

Receiver operator characteristics diagram with estimates of sensitivity and specificity for each of the 52 doctors stratified according to clinical experience. The boxes show the range of values for sensitivity and specificity for junior and senior doctors. The diagram contains 51 visible pairs of sensitivity and specificity since pairs of estimates were identical for two junior doctors and for two senior doctors.

Figure 3

Boxplot summarizing the distributions of κ values in 528 pairs of junior doctors and in 190 pairs of senior doctors.