Imaging for Right Lower Quadrant Pain in a Patient Without an Appendix
A KUB (kidney, ureter, bladder) radiograph is not the appropriate initial imaging study for a patient with sharp inspiratory right lower quadrant pain who has had a previous appendectomy. Instead, CT of the abdomen and pelvis with contrast is the recommended first-line imaging study 1.
Rationale for CT as First-Line Imaging
For patients with right lower quadrant pain who no longer have an appendix, CT imaging offers several advantages:
High diagnostic yield for alternative diagnoses: CT has excellent sensitivity and specificity for identifying numerous non-appendiceal causes of right lower quadrant pain 1.
Comprehensive evaluation: CT can detect a wide range of conditions affecting the:
- Gastrointestinal system (colitis, diverticulitis, inflammatory bowel disease)
- Genitourinary system (nephrolithiasis, pyelonephritis)
- Gynecologic system (in female patients)
- Hepatopancreaticobiliary system 1
Clinical impact: Studies show that CT findings frequently alter management plans, with 41% of patients with non-appendiceal diagnoses requiring hospitalization and 22% needing surgical or image-guided intervention 1.
Why KUB Is Insufficient
A KUB radiograph has several limitations in this scenario:
- Low sensitivity: Plain radiography has poor sensitivity for most causes of abdominal pain 1.
- Limited diagnostic value: The American College of Radiology rates abdominal radiography only a "4" (may be appropriate) on their 9-point scale for right lower quadrant pain, compared to "8" for CT with contrast 1.
- Specific indication: KUB is primarily useful when there is concern for perforation and free air, not for general evaluation of right lower quadrant pain 1.
Clinical Significance of Sharp Inspiratory Pain
Sharp pain that worsens with inspiration in the right lower quadrant suggests:
- Peritoneal irritation
- Possible inflammatory process adjacent to the diaphragm
- Potential for serious underlying pathology requiring prompt diagnosis
Alternative Diagnoses to Consider
Since appendicitis is ruled out in this patient, other diagnoses to consider include:
- Urinary tract conditions: Nephrolithiasis, ureteral stones (seen in approximately 3% of patients with RLQ pain) 1
- Colonic conditions: Right-sided diverticulitis (seen in 8% of RLQ pain cases), inflammatory bowel disease, infectious colitis 1
- Gynecologic conditions (in female patients): Ovarian torsion, tubo-ovarian abscess, ectopic pregnancy
- Other inflammatory conditions: Epiploic appendagitis, omental infarction, mesenteric adenitis 2
- Musculoskeletal causes: Iliopsoas bursitis 3
- Rare infections: Abdominal actinomycosis 4
Imaging Algorithm for RLQ Pain in Post-Appendectomy Patient
First-line: CT abdomen and pelvis with IV contrast
- Highest diagnostic yield for multiple potential etiologies
- Oral contrast may not be necessary depending on institutional preference 1
Alternative if radiation concerns exist:
- Ultrasound of abdomen/pelvis (particularly in female patients to evaluate gynecologic structures)
- MRI without contrast if ultrasound is inconclusive (especially in pregnant patients) 5
If initial imaging is negative but clinical suspicion remains high:
- Consider diagnostic laparoscopy, which has been shown to alter management in 31.1% of patients with right lower quadrant pain 6
Important Clinical Considerations
- The absence of an appendix significantly broadens the differential diagnosis for right lower quadrant pain
- Delaying appropriate imaging may lead to delayed diagnosis of serious conditions
- The inspiratory component of the pain suggests peritoneal irritation, which warrants thorough evaluation
- Diagnostic accuracy is crucial as studies show that alternative diagnoses often require intervention 1
Remember that while CT involves radiation exposure (approximately 10 mSv), the diagnostic benefit outweighs the risk in most adult patients with acute abdominal pain 1.