What's the next step in evaluating a patient with right lower quadrant pain radiating to the right lower back, with unremarkable CT (Computed Tomography) of the abdomen and pelvis without IV (Intravenous) contrast and lumbar spine x-rays?

Next Step: Repeat CT with Intravenous Contrast

The next step is to obtain a CT of the abdomen and pelvis WITH intravenous contrast, as the initial non-contrast CT has significantly limited diagnostic capability for evaluating right lower quadrant pain. 1, 2

Why the Initial CT Was Inadequate

• Non-contrast CT has substantially lower sensitivity (90-91%) compared to contrast-enhanced CT (96-97%) for detecting appendicitis and other acute pathology. 1
• The ACR Appropriateness Criteria explicitly state that CT with IV contrast is "usually appropriate" for right lower quadrant pain, while non-contrast CT is only appropriate when the patient cannot receive IV contrast. 1
• Contrast-enhanced CT identifies alternative diagnoses in 23-45% of cases presenting with right lower quadrant pain, which is critical given the broad differential for pain radiating to the lower back. 2

Specific Diagnostic Advantages of IV Contrast

• Contrast enhancement significantly improves visualization of inflammatory processes, vascular pathology, and soft tissue abnormalities that could explain the radiating back pain pattern. 1
• For appendicitis specifically, contrast-enhanced CT achieves 95% sensitivity and 94% specificity, compared to 91% sensitivity for non-contrast studies. 1
• CT with IV contrast excels at detecting non-appendiceal causes including right colonic diverticulitis (8% of RLQ pain cases), bowel obstruction (3%), infectious enterocolitis, inflammatory terminal ileitis, and ureteral stones—all of which can radiate to the back. 1

Alternative Imaging Considerations

• Ultrasound is not recommended as the next step after an unremarkable CT, as it has lower sensitivity for deep pathology and would represent a step backward in diagnostic capability. 2
• MRI abdomen and pelvis without IV contrast could be considered if there is a contraindication to IV contrast, with 85-98% sensitivity for appendicitis and ability to identify alternative diagnoses in 52% of cases. 3

Critical Pitfall to Avoid

• Do not proceed to diagnostic laparoscopy or surgical exploration without definitive imaging confirmation, as this risks both negative exploration and missing the actual pathology. 2
• The radiating back pain pattern suggests possible retroperitoneal involvement, psoas inflammation, or referred pain from pelvic pathology—all better characterized with contrast-enhanced imaging. 4, 5

If Contrast-Enhanced CT Remains Negative

• Consider targeted ultrasound for gynecologic pathology (ovarian torsion, hemorrhagic cyst, pelvic inflammatory disease) if the patient is female. 3
• Evaluate for musculoskeletal causes including psoas abscess or iliopsoas pathology if imaging remains unrevealing. 4
• Reassess at 3-7 days if symptoms persist without identified pathology, as some conditions evolve over time. 3