Evaluation of Right Lower Quadrant Pain in a 21-Year-Old Female
Start with CT abdomen and pelvis with IV contrast as your initial imaging study—this achieves 95% sensitivity and 94% specificity for appendicitis while simultaneously identifying alternative diagnoses in up to 45% of cases. 1
Initial Clinical Assessment
Focus your history and physical on these specific findings:
- Migration pattern: Periumbilical pain migrating to RLQ suggests appendicitis 1
- Associated symptoms: Anorexia, nausea, vomiting, fever 1
- Gynecologic history: Last menstrual period, sexual activity, contraception use, vaginal discharge 1
- Physical exam: Rebound tenderness, guarding, McBurney's point tenderness 1
- Urinary symptoms: Dysuria, frequency, hematuria to assess for UTI/nephrolithiasis 1
Imaging Algorithm
First-Line: CT Abdomen/Pelvis with IV Contrast
CT is the workhorse for RLQ pain in adults, providing definitive diagnosis in a single study. 1
- Diagnostic performance: 95% sensitivity, 94% specificity for appendicitis 1
- Alternative diagnoses detected: Right colonic diverticulitis (8%), bowel obstruction (3%), ovarian pathology, infectious enterocolitis, ureteral stones, inflammatory bowel disease 1
- Clinical impact: 41% of patients with non-appendiceal diagnoses require hospitalization, 22% need surgical/interventional procedures 1
Alternative: Ultrasound First Strategy
Consider pelvic ultrasound (transabdominal + transvaginal) ONLY if gynecologic pathology is your primary concern and you want to avoid radiation. 2
When ultrasound is appropriate:
- Strong clinical suspicion for ovarian torsion, ovarian cyst, or tubo-ovarian abscess 2
- Patient specifically concerned about radiation exposure 2
- Experienced sonographer immediately available 2
Critical limitations of ultrasound:
- Appendix not visualized in 20-81% of cases, creating diagnostic uncertainty 2
- Sensitivity ranges wildly from 21% to 95.7% depending on operator skill and patient body habitus 2
- Equivocal results require CT anyway, causing diagnostic delay without avoiding radiation 2
- False-positive rates are higher in females 2
Differential Diagnosis Beyond Appendicitis
Your CT will evaluate for these conditions simultaneously 1, 3:
Gastrointestinal causes:
- Right colonic diverticulitis (mimics appendicitis exactly) 1
- Inflammatory bowel disease (Crohn's terminal ileitis) 1
- Infectious enterocolitis/typhlitis 1
- Mesenteric adenitis 3
- Epiploic appendagitis 3
Gynecologic causes:
- Ovarian torsion (surgical emergency) 2
- Ruptured ovarian cyst 2
- Tubo-ovarian abscess 1
- Ectopic pregnancy (if sexually active) 2
- Pelvic inflammatory disease 1
Urologic causes:
Vascular causes:
- Mesenteric ischemia (rare in this age group) 4
Common Pitfalls to Avoid
- Don't assume normal labs exclude serious pathology: Inflammatory markers can be normal early in appendicitis or with perforation 2
- Don't delay imaging for "observation": In a 21-year-old female, the differential is too broad and consequences of missed diagnosis (perforated appendicitis, ovarian torsion) are too severe 1
- Don't order ultrasound first if appendicitis is your leading diagnosis: You'll likely need CT anyway, causing unnecessary delay 2
- Don't forget pregnancy test: Essential before any imaging in reproductive-age females 1
If Patient is Pregnant
The algorithm changes completely—start with ultrasound, then MRI if inconclusive, reserving low-dose CT only when MRI unavailable. 1
- US + MRI combination is most commonly used (41% of cases) 1
- MRI performance in pregnancy: 96.8% sensitivity, 99.2% specificity for appendicitis 1
- Low-dose CT can be used when MRI not immediately available: 83% conclusive diagnosis rate 1
- Risk of perforation: Pregnant women present later with higher perforation rates and increased fetal loss risk 1