Diagnostic Imaging for Chronic Diarrhea

Initial Imaging Recommendations

• The American College of Radiology recommends CT of the abdomen and pelvis with IV contrast as the initial outpatient imaging study for patients with chronic diarrhea, negative stool cultures, and left lower quadrant abdominal cramping, due to its superior diagnostic accuracy of 98% for detecting colonic inflammation 1, 2
• CT is preferred for its comprehensive assessment, which can evaluate both intraluminal and extraluminal pathology, crucial for diagnosing conditions like diverticulitis that may present with chronic diarrhea and LLQ pain, and can detect complications such as abscesses, fistulas, or strictures that may be causing chronic symptoms 1, 2

Contrast Enhancement and Radiation Considerations

• IV contrast enhancement improves characterization and detection of subtle bowel wall abnormalities and complications, while oral contrast may be beneficial but is not always necessary for diagnosis 1
• Low-dose CT techniques can achieve 75-90% radiation dose reduction compared to standard protocols while maintaining similar sensitivity and specificity 2

Alternative Imaging Modalities

• Ultrasound may be considered if CT is contraindicated or unavailable, but has limitations including lower sensitivity (61% vs 81% for CT) and is operator-dependent 1, 2
• MRI may be considered in patients with contraindications to CT or concerns about radiation exposure, with comparable sensitivity (86-94%) and specificity (88-92%) to CT for some conditions 2
• Plain radiography and fluoroscopic contrast enema are not recommended as initial imaging tests due to limited sensitivity and specificity, and risk of perforation, respectively 1, 2

Special Considerations

• Female patients of reproductive age should be considered for transvaginal ultrasound first if gynecologic pathology is suspected 1, 2
• Clinicians should be mindful of cumulative radiation exposure, especially in younger patients, and consider alternative imaging modalities when possible 2
• Double contrast studies should be avoided in patients with active diverticulitis due to the increased risk of colonic perforation, and should be delayed until complete resolution of acute symptoms, typically 6-8 weeks, as recommended by the American College of Radiology and the American Gastroenterological Association 1, 2, 3
• Single contrast studies may have limited roles in follow-up evaluation after resolution of acute symptoms, assessment of complications after complete resolution of acute diverticulitis, and pre-surgical planning for chronic complications, as suggested by the American College of Radiology 1, 2

1, 2, 4