The Value of Bowel Sounds in Evaluating Postoperative Intestinal Function Recovery in Colorectal Cancer Patients: A Prospective Cohort Study

Colorectal cancer (CRC) is the third most common malignancy worldwide and the second leading cause of cancer-related mortality. In recent years, both the incidence and mortality of colorectal cancer in China have shown a significant upward trend. With population aging and lifestyle changes, the disease is increasingly affecting younger individuals, with the proportion of patients under 40 years of age steadily rising. Treatment strategies vary according to disease stage; however, for most cases amenable to primary resection, surgical intervention remains the cornerstone of therapy.

With the widespread implementation of Enhanced Recovery After Surgery (ERAS) protocols, postoperative rehabilitation has been substantially improved through optimization of preoperative, intraoperative, and postoperative management strategies, such as shortened preoperative fasting, the use of laparoscopic techniques, and early postoperative oral intake, thereby facilitating accelerated recovery and earlier discharge. Following curative surgery for colorectal cancer, patients commonly experience reduced or transiently absent intestinal motility due to surgical manipulation and the effects of anesthesia, with gradual return to normal function over several days. Early postoperative feeding has been shown to promote gastrointestinal functional recovery.

However, a subset of patients may exhibit delayed recovery of bowel function, characterized by diminished bowel sound activity, prolonged time to first flatus, and often accompanied by abdominal distension. Postoperative ileus (POI) is one of the most common causes of delayed postoperative gastrointestinal recovery and typically presents as transient suppression of gastrointestinal motility. When the duration exceeds the expected physiological range, potential pathological conditions, such as early postoperative small bowel obstruction (EPSBO), should be considered. In such circumstances, oral intake may exacerbate the ileus and even precipitate intestinal obstruction. Therefore, timely differentiation and accurate diagnosis of the patient's postoperative gastrointestinal status are of critical importance.

Abdominal auscultation, as a noninvasive diagnostic technique, has a history spanning several centuries. In 1905, Cannon was the first to report systematic investigations of abdominal auscultation, proposing that regular bowel sounds are generated by intestinal peristaltic activity. Subsequent studies have demonstrated that bowel sounds vary by anatomical location: sounds originating from the small intestine are typically high-pitched, high-amplitude, and frequent, whereas colonic sounds are lower in frequency, weaker in amplitude, and less frequent. Postoperatively, the recovery of gastrointestinal motility differs among intestinal segments, with the small intestine recovering first, followed by the stomach and the colon.

Abdominal auscultation has been widely used as an adjunctive tool in the evaluation of conditions such as intestinal obstruction and ileus owing to its immediacy and convenience and is commonly applied in patients with delayed postoperative gastrointestinal recovery. However, the reliability of auscultation-based assessment remains controversial because of the inherent subjectivity in clinicians' descriptions of bowel sounds. A prospective study by Felder et al. demonstrated a low sensitivity of 22%-32% for manual auscultation in distinguishing healthy from diseased individuals, along with low positive predictive values of 23%-44%. Similarly, Thomas et al. conducted a prospective study examining the relationship between auscultated bowel sounds and postoperative oral tolerance and flatus, finding no significant correlation between bowel sounds and postoperative abdominal distension, flatus, defecation, or tolerance of oral intake.