Is ultrasound a suitable initial imaging test for a patient presenting with left lower quadrant (LLQ) pain?

Ultrasound for Left Lower Quadrant Pain

Ultrasound is an appropriate initial imaging test for left lower quadrant (LLQ) pain in specific patient populations, particularly premenopausal women with suspected gynecologic pathology, but CT is generally preferred for most patients with LLQ pain due to its superior diagnostic accuracy. 1

Patient-Specific Imaging Recommendations

Premenopausal Women

• Pelvic/transvaginal ultrasound is the preferred initial imaging modality when gynecologic pathology is suspected in premenopausal women with LLQ pain 1, 2
• Ultrasound can effectively evaluate ovarian cysts, ectopic pregnancy, pelvic inflammatory disease, and other gynecologic conditions that may present with LLQ pain 2, 3
• When gynecologic findings on ultrasound are negative or equivocal but symptoms persist, CT should be considered as the next step 4, 2

General Adult Population

• CT abdomen and pelvis with contrast is the preferred initial imaging test for most patients with LLQ pain, particularly when diverticulitis is suspected 1
• CT offers superior diagnostic accuracy (98%) for diverticulitis and better detection of alternative diagnoses 1
• CT allows for evaluation of disease severity, identification of complications (perforation, abscess, fistula), and appropriate treatment planning 1

Role of Transabdominal Ultrasound

• Transabdominal ultrasound may be used to reduce unnecessary CT examinations in selected cases 1
• Benefits include:
  • Real-time, non-invasive evaluation 1
  • Can be directed to the area of maximal pain 1
  • No ionizing radiation exposure 1
• Limitations include:
  • Variable sensitivity (77-98%) and specificity (80-99%) for diverticulitis 1
  • Highly operator-dependent 1
  • Technical difficulties in patients who are obese 1
  • Less commonly used in the United States for non-gynecologic LLQ pain 1

Clinical Considerations

Suspected Diverticulitis

• The classic triad of LLQ pain, fever, and leukocytosis is present in only 25% of diverticulitis cases 1
• Misdiagnosis based on clinical assessment alone occurs in 34-68% of cases 1
• CT is superior for:
  • Evaluating disease severity and extent 1
  • Detecting complications like perforation, abscess, or fistula 1
  • Identifying alternative diagnoses with similar presentations 1

Other Imaging Modalities

• Plain radiography is not useful as an initial test for LLQ pain due to limited sensitivity 1
• MRI has superior soft tissue resolution but is:
  • More time-consuming to perform 1
  • More expensive 1
  • Less sensitive for extraluminal air and urinary tract calculi 1
  • Not recommended as initial imaging for acute LLQ pain 1
• Contrast enema is not recommended as an initial test due to:
  • Lower sensitivity than CT 1
  • Inability to show extraluminal abnormalities 1
  • Risk of perforation in acute diverticulitis 1

Common Pitfalls and Caveats

• Ultrasound may miss non-gynecologic causes of LLQ pain that can be detected by CT 1, 5
• When gynecologic pathology is initially suspected but ultrasound is negative, consider CT to evaluate for gastrointestinal causes 4, 5
• In patients with known diverticulitis and mild recurrent symptoms, imaging may not be necessary 1
• CT with IV contrast is preferred over non-contrast CT for better delineation of abscesses and inflammatory changes 1
• Consider the differential diagnosis of LLQ pain beyond diverticulitis, including colitis, urolithiasis, epiploic appendagitis, and retroperitoneal pathology 6