Colonic stool burden on computed tomography does not correlate with bowel habit: a cross-sectional study

Purpose: Stool burden on abdominal radiographs is not reflective of constipation, perhaps because of variable fecal shadowing or limited inter-rater agreement. These limitations are hypothetically mitigated by computed tomography (CT). This research aimed (i) to evaluate whether bowel movement frequency, stool form, or a diagnosis of functional constipation correlate or associate with stool burden identified on CT, and (ii) to investigate whether physicians use CT in their assessment of a patients’ bowel function. Methods: Patients attending for non-emergent abdominal CT imaging were invited to participate by completing a bowel questionnaire. Stool burden identified on imaging was determined and inter-rater reliability was evaluated in a subgroup of patients (n = 20). Descriptive and comparative analyses were performed. An online questionnaire evaluated the use of abdominal imaging in assessing patients’ bowel function in a cross-section of ordering physicians. Results: The patient response rate was 19% (96/516). No clinically useful associations between fecal burden and stool form, bowel motion frequency, gastrointestinal symptoms or a diagnosis of constipation was identified. The physician response rate was 35% (33/94). Opportunistic use of data was more common than deliberate use. However, an abdominal radiograph or CT scan had been requested by 42% and 18% of physicians respectively to assess patient’s chronic bowel habit. Approximately 30% of physicians believed evidence supported this practice. Conclusions: Physicians may use abdominal CT in their assessment of patients’ chronic bowel habits. However, objective assessment does not support this practice. Colonic stool burden does not correlate with patient-reported symptoms or a criteria-based diagnosis of constipation.