What is the initial workup for a patient presenting with right lower quadrant abdominal pain?

Workup for Right Lower Quadrant Abdominal Pain

Computed tomography (CT) with intravenous contrast is the initial imaging study of choice for evaluating patients with right lower quadrant abdominal pain, with a sensitivity of 95% and specificity of 94% for detecting appendicitis and other causes of right lower quadrant pain. 1, 2

Initial Clinical Assessment

• Evaluate for key symptoms and signs:

  • Pain characteristics (onset, duration, migration, severity)
  • Associated symptoms (nausea, vomiting, fever, anorexia)
  • Focused physical exam for:
    • Localized tenderness at McBurney's point
    • Guarding and rigidity
    • Rovsing's sign (pain in RLQ when pressing LLQ)
    • Psoas sign and obturator sign

• Laboratory studies:

  • Complete blood count (CBC) with differential
  • C-reactive protein (CRP)
  • Urinalysis
  • Pregnancy test in women of reproductive age (critical before imaging) 1
  • Consider liver function tests and lipase if indicated

Imaging Algorithm

1. CT with IV contrast: First-line imaging for most adults with RLQ pain

   • Highest diagnostic accuracy (sensitivity 96%, specificity 94-100%) 2
   • Excellent for identifying alternative diagnoses
   • Changes management in up to 42% of cases 2

2. Ultrasonography: Consider as first-line in:

   • Pregnant patients
   • Children
   • Young, thin adults
   • Patients with contraindications to CT contrast
   • Note: Lower sensitivity (76%) compared to CT (96%) 2
   • Significantly limited in obese patients (BMI >37 kg/m²) 2

3. Non-contrast CT: Acceptable alternative when:

   • IV contrast is contraindicated (renal insufficiency, contrast allergy)
   • Sensitivity approximately 90% 2

4. MRI without contrast: Consider when:

   • Pregnant patients with non-diagnostic ultrasound
   • Patients who cannot receive radiation or contrast

Common Diagnoses to Consider

• Appendicitis (most common surgical cause)
• Right colonic diverticulitis (8% of RLQ pain cases) 2
• Bowel obstruction (3% of RLQ pain cases) 2
• Inflammatory bowel disease
• Mesenteric adenitis
• Urolithiasis
• Gynecologic conditions (ovarian torsion, PID, ectopic pregnancy)
• Epiploic appendagitis
• Omental infarction
• Infectious enterocolitis 3, 4

Important Clinical Pitfalls

1. Do not delay imaging in patients with classic appendicitis symptoms 2
2. Do not rule out appendicitis based on absence of fever or normal WBC count, as 15.6% of confirmed appendicitis cases present with isolated RLQ pain without fever or elevated inflammatory markers 2
3. Do not use ultrasound as first-line in obese patients due to significantly reduced accuracy 2
4. Do not start antibiotics before confirming diagnosis, as this may mask findings 2
5. Do not rely solely on clinical assessment for appendicitis, as this historically leads to high negative appendectomy rates 2
6. Avoid plain radiographs for suspected appendicitis - they have limited diagnostic value (rated only 4/9 by ACR) 1, 2

CT with IV contrast not only provides the highest diagnostic accuracy but also increases physician diagnostic certainty from 70.5% to 92.2%, prevents delays in diagnosis and treatment, and guides appropriate management, particularly in patients where clinical presentation may be atypical or confusing 2.