How to manage a patient with right lower quadrant (RLQ) pain and no leukocytosis (elevated white blood cell count), considering the possibility of referred pain?

Management of Right Lower Quadrant Pain Without Leukocytosis

CT abdomen and pelvis with IV contrast is the imaging modality of choice for evaluating RLQ pain without leukocytosis, as it provides superior diagnostic accuracy (95% sensitivity, 94% specificity) for appendicitis while simultaneously identifying alternative diagnoses that frequently require intervention. 1

Initial Diagnostic Approach

Imaging Strategy

• CT abdomen and pelvis remains the primary imaging modality even in the absence of leukocytosis, as the "classic" presentation of appendicitis (including fever and leukocytosis) occurs in only approximately 50% of patients 1
• CT identifies the cause of RLQ pain in the majority of cases, with 41% of patients with non-appendiceal diagnoses requiring hospitalization and 22% requiring surgical or image-guided intervention 1
• The absence of elevated WBC does not exclude appendicitis or other serious pathology requiring urgent treatment 1

Contrast Protocol Selection

• Contrast-enhanced CT without enteral contrast achieves sensitivities of 90-100% and specificities of 94.8-100% for appendicitis, avoiding delays associated with oral contrast administration 1
• Non-enhanced CT has lower sensitivity (85.7%) but meta-analysis shows acceptable performance (90% sensitivity, 94% specificity) if contrast is contraindicated 1

Differential Diagnosis Beyond Appendicitis

Common Alternative Diagnoses

When CT excludes appendicitis in patients with RLQ pain and normal WBC, the most frequent diagnoses include: 1

• Gynecologic conditions: Benign adnexal masses, ovarian pathology (refer to ACR criteria for acute pelvic pain if this is primary concern)
• Gastrointestinal etiologies: Gastroenteritis, colitis, inflammatory bowel disease, right-sided diverticulitis, constipation
• Genitourinary causes: Urolithiasis (refer to ACR criteria for flank pain if primary concern)
• Vascular: Pelvic congestion syndrome
• Musculoskeletal: Iliopsoas bursitis (uncommon but documented) 2

Critical Pitfall: Referred Pain Considerations

• Right upper quadrant pathology can present as RLQ pain through referred mechanisms 1
• Biliary disease (cholecystitis, choledocholithiasis) should be considered if imaging does not reveal RLQ pathology 1
• Ensure CT field of view includes the entire abdomen and pelvis to avoid missing referred sources 1

Role of Ultrasound

Performance Limitations

• Ultrasound has significantly lower sensitivity (51.8%) and specificity (81.4%) compared to CT in the general population with RLQ pain 1
• Appendix non-visualization occurs in 27.7-45% of cases, limiting diagnostic confidence 1
• When appendix is not visualized, indirect signs yield highly variable sensitivity (31.8-83.9%) and specificity (56.7-96.7%) 1
• Negative appendectomy rate with ultrasound alone is 38.4% versus 1.7-7.7% with CT 1

Appropriate Ultrasound Use

• Consider as initial modality only in reproductive-age females where gynecologic pathology is primary concern 1
• If ultrasound is non-diagnostic or equivocal, proceed directly to CT rather than clinical observation alone 1

MRI Considerations

• MRI with diffusion-weighted imaging (DWI) achieves specificity and positive predictive value of 100% with sensitivity 97-99% for appendicitis 1
• Reserve for pregnant patients or when radiation exposure is contraindicated 1
• DWI sequences increase appendix conspicuity and reader confidence 1

Management Algorithm

1. Obtain CT abdomen and pelvis with IV contrast as first-line imaging for RLQ pain without leukocytosis 1
2. If CT shows appendicitis: Proceed to surgical consultation regardless of WBC count 1
3. If CT shows alternative diagnosis: Direct management toward specific pathology identified (94.3% concordance with final clinical diagnosis) 1
4. If CT is negative: Consider referred pain from upper abdomen, musculoskeletal causes, or functional disorders 1, 2
5. In immunocompromised patients: Maintain high suspicion for atypical presentations including typhlitis, which requires urgent diagnosis via contrast-enhanced CT 3

Key Clinical Caveats

• Never rely on normal WBC alone to exclude appendicitis or other surgical pathology—imaging is mandatory 1
• CT changes management in 43% of patients initially suspected to have appendicitis clinically 1
• In patients without final CT diagnosis, only 14% require hospitalization and 4% require intervention, supporting CT's role in avoiding unnecessary procedures 1
• Ensure complete evaluation of the entire abdomen and pelvis to identify referred pain sources 1