What imaging should I order for a patient with left lower quadrant pain?

Imaging for Left Lower Quadrant Pain

CT of the abdomen and pelvis with intravenous contrast is the preferred imaging modality for patients with left lower quadrant pain, particularly when diverticulitis is suspected. 1

First-Line Imaging

• CT with IV contrast has the highest rating (8-9/9) on the American College of Radiology Appropriateness Criteria for left lower quadrant pain, with reported overall accuracy of 98% for diagnosing diverticulitis 1
• CT provides comprehensive assessment of disease severity, aids in treatment planning, and can identify alternative diagnoses that may mimic diverticulitis 1
• The value of CT extends beyond diagnosis to stratifying patients for operative versus nonoperative treatment based on imaging features 1
• Oral or colonic contrast may be added to help with bowel luminal visualization, though IV contrast is most important for detecting inflammation and complications 1

Specific Benefits of CT for Left Lower Quadrant Pain

• CT is highly sensitive for detecting small amounts of extraluminal air, which can indicate perforation requiring surgical intervention 1
• CT can identify complications of diverticulitis such as abscesses, fistulas, and pericolonic inflammation that other modalities may miss 1
• CT allows visualization of both intra- and extra-colonic pathology, which is crucial as many causes of left lower quadrant pain originate from the colon but may extend beyond it 2
• Low-dose CT techniques can achieve 75-90% radiation dose reduction compared to standard protocols while maintaining similar sensitivity and specificity 1

Alternative Imaging Options

MRI Abdomen and Pelvis

• May be appropriate (rated 4-5/9) in select cases, particularly when avoiding radiation is critical 1
• Preliminary data shows sensitivity of 86-94% and specificity of 88-92% for diverticulitis 1
• Limited by longer acquisition time, motion artifacts in acutely ill patients, and reduced sensitivity for extraluminal air 1

Ultrasound

• Transabdominal ultrasound is rated as "may be appropriate" (4/9) 1
• Can be useful to reduce CT usage without negative impact on patient care 1
• Particularly valuable in premenopausal women to evaluate for gynecologic causes of pain before proceeding to CT 1

Abdominal Radiography

• Limited utility (rated 4/9) for left lower quadrant pain 1
• May detect large amounts of free air or bowel obstruction but is significantly less sensitive than CT 1
• Not recommended as an initial imaging test due to poor sensitivity for most causes of left lower quadrant pain 1

Special Considerations

• In premenopausal women, consider transvaginal ultrasound first to evaluate for gynecologic causes before proceeding to CT 1, 3
• Unenhanced CT may be appropriate (rated 6/9) when IV contrast is contraindicated, though it has reduced sensitivity for inflammatory changes 1
• CT should cover both abdomen and pelvis, as limiting the scan to just the pelvis could miss important pathology 4
• Contrast enema has been largely supplanted by CT and is not recommended as an initial imaging test 1

Common Pitfalls to Avoid

• Failing to consider gynecologic causes in women of reproductive age, which may require ultrasound before or instead of CT 1, 3
• Missing anatomic variants such as intestinal malrotation that can present with left-sided symptoms from typically right-sided structures 5
• Using only pelvic-focused CT, which can miss important pathology in the abdomen 4
• Relying solely on clinical diagnosis without imaging, as misdiagnosis based on clinical assessment alone occurs in 34-68% of cases 1