What type of imaging should be ordered for a patient with abdominal pain?

Imaging Selection for Patients with Abdominal Pain

For patients with abdominal pain, CT of the abdomen and pelvis with IV contrast is the most appropriate initial imaging study due to its superior diagnostic accuracy and ability to detect a wide range of pathologies. 1

Initial Imaging Selection Based on Clinical Presentation

Nonlocalized Abdominal Pain

• CT abdomen and pelvis with IV contrast is the preferred initial imaging modality for nonlocalized abdominal pain, as it can detect a broad range of pathologies and has been shown to change the leading diagnosis in 49% of patients and alter management plans in 42% of patients 1
• If IV contrast is contraindicated, CT without contrast is an appropriate alternative 1
• MRI abdomen and pelvis without and with IV contrast can provide clinically useful information but is less readily available in emergency settings 1
• Conventional radiography (X-ray) has limited diagnostic value for abdominal pain and rarely changes patient treatment 1

Right Upper Quadrant Pain

• Ultrasound is recommended as the initial imaging test for right upper quadrant pain to evaluate for gallbladder disease 1
• Ultrasound has a sensitivity of 81% and specificity of 83% for detecting acute cholecystitis, can identify other potential causes of pain, and avoids radiation exposure 1, 2
• CT may be considered for patients with inconclusive ultrasound results or to help guide surgical planning 1
• MRI can be used in patients with equivocal ultrasound findings or to visualize hepatic and biliary abnormalities that cannot be characterized on ultrasound 1

Left Lower Quadrant Pain

• CT is recommended as the initial imaging test for left lower quadrant pain, particularly when diverticulitis is suspected 1
• CT has a sensitivity of greater than 95% for detecting diverticulitis and can provide information about disease extent and complications 1
• Ultrasound may be used as an alternative but has variable sensitivity compared to CT and is highly operator-dependent 1

Special Considerations

Pregnant Patients

• Ultrasound should be the primary imaging modality for pregnant patients with abdominal pain 1
• For equivocal findings, noncontrast MRI is recommended as the follow-up imaging study 1

Patients with Fever

• CT abdomen and pelvis with IV contrast is the preferred imaging study for patients with abdominal pain and fever to evaluate for abscesses and other infectious/inflammatory processes 1
• CT can detect various conditions including abscesses, colitis, inflammatory bowel disease, cholecystitis, and pelvic inflammatory disease 1

Suspected Specific Conditions

Suspected Cyst Hemorrhage

• Ultrasound (showing sediment or mobile septations) and/or MRI (heterogeneous and intense signal on both T1- and T2-weighted sequences) may be used to diagnose cyst hemorrhage 1
• CT is not recommended to diagnose cyst hemorrhage 1

Suspected Hepatic Cyst Infection

• MRI showing high signal intensity on diffusion-weighted images, fluid-fluid level, wall thickening, or gas in at least one cyst may indicate hepatic cyst infection 1
• 18FDG PET-CT showing increased FDG activity lining a cyst compared to normal parenchyma is useful for diagnosing hepatic cyst infection 1

Practical Algorithm for Imaging Selection

1. First, determine if pain is localized or nonlocalized:

   • If nonlocalized: CT abdomen/pelvis with IV contrast 1
   • If localized: Proceed based on quadrant

2. For localized pain:

   • Right upper quadrant: Start with ultrasound 1, 2
   • Left lower quadrant: Start with CT with IV contrast 1
   • Other quadrants: CT with IV contrast is generally preferred 1

3. Special situations:

   • Pregnancy: Ultrasound first, then noncontrast MRI if needed 1
   • Suspected biliary disease: Ultrasound first 1, 3
   • Suspected pancreatic disease: CT with IV contrast, though ultrasound may be useful initially 4

Common Pitfalls to Avoid

• Relying solely on conventional radiography, which has limited diagnostic value for abdominal pain 1
• Failing to use IV contrast with CT when not contraindicated, as it increases the spectrum of detectable pathology 1
• Using CT as the first-line imaging for right upper quadrant pain when ultrasound is more appropriate and avoids radiation exposure 1
• Not considering MRI for specific conditions like cyst hemorrhage where it provides superior diagnostic information 1