Will a CT (Computed Tomography) scan show constipation?

Will a CT Scan Show Constipation?

A CT scan is not an appropriate imaging modality for diagnosing or evaluating functional constipation, as there is no relevant literature supporting its use for this purpose and colonic stool burden on CT does not correlate with patient-reported bowel symptoms or constipation diagnosis. 1

CT's Limited Role in Constipation

What CT Cannot Do

• CT has no established role in functional assessment of constipation or defecatory dysfunction according to the American College of Radiology guidelines 1
• Recent research definitively demonstrates that colonic stool burden identified on CT does not correlate with bowel movement frequency, stool form, gastrointestinal symptoms, or a criteria-based diagnosis of functional constipation 2
• Inter-rater reliability for assessing stool burden on CT, while better than plain radiographs, still does not translate to clinically useful information about a patient's actual bowel function 2

What CT Can Show Instead

CT may be appropriate only when evaluating for mechanical causes of acute constipation or obstruction, not chronic functional constipation:

• Acute colonic obstruction from masses, volvulus (sigmoid or cecal), or other structural abnormalities 1, 3
• Anatomic conditions in the pelvic floor at rest that may result in obstructed defecation, such as masses or other structural lesions 1
• Complications of obstruction including perforation, ischemia, or abscess formation 1

Appropriate Imaging for Constipation

For Chronic Functional Constipation

The evidence supports these modalities instead:

• Plain abdominal radiographs can show the extent of fecal impaction in chronic constipation, though this has limited clinical utility 3
• Colonic transit time studies using serial abdominal radiographs after ingestion of radiopaque markers can distinguish hypertonic from atonic constipation 3, 4
• Fluoroscopic defecography (cystocolpoproctography) is the initial imaging test of choice for evaluating defecatory dysfunction, revealing structural abnormalities like rectoceles, enteroceles, sigmoidoceles, and rectal intussusception 1

For Acute Presentations Suggesting Obstruction

• CT with IV contrast is appropriate when acute colonic obstruction is suspected based on acute onset of symptoms, abdominal distension, and absence of flatus/stool passage 1
• Plain radiographs may suffice to determine the level and cause of obvious mechanical obstruction like volvulus 3
• Barium enema or colonoscopy can detect the cause of obstruction when CT is unavailable 1

Critical Clinical Pitfall

Approximately 42% of physicians have inappropriately requested abdominal imaging (radiographs or CT) to assess patients' chronic bowel habits, despite lack of evidence supporting this practice 2. This represents wasteful healthcare spending and unnecessary radiation exposure without diagnostic benefit. The disconnect between physician practice patterns and actual evidence is substantial, with about 30% of physicians incorrectly believing evidence supports using CT for chronic constipation assessment 2.

When to Suspect Something Other Than Simple Constipation

Order CT imaging when clinical features suggest mechanical obstruction or serious structural pathology rather than functional constipation:

• Acute onset of constipation (suggests obstruction) 3
• Complete absence of flatus and stool passage 1
• Severe abdominal distension with tenderness 1
• Signs of peritonitis, fever, or systemic toxicity 1
• Bloody stools or rectal bleeding 1
• Known or suspected malignancy 1