Appendicitis: Alvarado Score, Imaging, and Appendectomy
Appendicitis is the most common abdominal surgical emergency. Peak incidence is 10–30 years of age. Lifetime risk is ~7%. Missing it leads to perforation (30% rate) with peritonitis and sepsis; overtreating it leads to unnecessary surgery. Risk stratification and appropriate imaging prevent both errors.
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Evidence-based · For exam prep, not medical advice
update Updated October 2026
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Built by surgery and anesthesiology residents·Written for USMLE Step 1
Classic progression: periumbilical colicky pain → migration to RLQ (McBurney's point — 1/3 of the way from ASIS to umbilicus) → nausea/vomiting → fever → RLQ tenderness + guarding. Rebound tenderness and Rovsing sign (LLQ pressure → RLQ pain) support peritoneal irritation. Psoas sign: RLQ pain with right hip extension (retrocecal appendix). Obturator sign: RLQ pain with internal rotation of flexed right hip (pelvic appendix). Alvarado (MANTRELS) score: Migration of pain to RLQ (1), Anorexia (1), Nausea/vomiting (1), Tenderness at McBurney's (2), Rebound tenderness (1), Elevated temperature (1), Leukocytosis (2) = max 10. Score ≤4: low risk (likely not appendicitis); 5–6: equivocal (imaging); 7–10: high risk (likely appendicitis, consider direct to OR in classic presentation).
Imaging
CT abdomen/pelvis with IV contrast: gold standard — sensitivity 98%, specificity 98%. Findings: appendix diameter >6mm, periappendiceal fat stranding, appendicolith (calcified fecalith — 20% of cases but high specificity), non-opacification of appendiceal lumen. Ultrasound: preferred in children and pregnant women (no radiation). Sensitivity 75–90% (operator-dependent), specificity 90%. Findings: non-compressible tubular structure >6mm. MRI: best in pregnancy when ultrasound is equivocal — no radiation, good sensitivity for perforation. Plain films: largely unhelpful — appendicolith on KUB is only classic finding. Algorithm: Children and pregnant women → ultrasound first. Adults with classic presentation (Alvarado ≥7) → CT or direct to OR. Adults with equivocal presentation → CT.
Management
Uncomplicated appendicitis: laparoscopic appendectomy (gold standard — faster recovery, lower wound infection than open). Non-operative management (IV antibiotics alone) is effective in ~70% of uncomplicated cases without appendicolith, but recurrence rate ~30% at 5 years — shared decision-making with patient. Antibiotics: ceftriaxone + metronidazole OR piperacillin-tazobactam for 24–48h pre-op. Complicated (perforated/gangrenous) appendicitis: if hemodynamically stable with formed abscess → CT-guided drainage + antibiotics, then interval appendectomy 6–8 weeks later. If peritonitis or hemodynamically unstable → urgent open or laparoscopic appendectomy + washout. Broad-spectrum antibiotics post-operatively for 4–5 days.
quiz Test yourself
Quick check — 3 questions
1. A 19-year-old presents with 18 hours of periumbilical pain that migrated to the RLQ, anorexia, nausea, temp 38.2°C, and WBC 14,500. His Alvarado score is 8. CT shows an appendix 9mm in diameter with periappendiceal fat stranding. The next step is:
Explanation. Alvarado score 8 + classic clinical features + CT confirming uncomplicated appendicitis → laparoscopic appendectomy. Non-operative management (antibiotics alone) is an option for uncomplicated appendicitis in selected patients but requires shared decision-making. This patient has a classic presentation with CT confirmation — surgery is the standard of care and most reliable treatment.
2. RLQ pain worsened by internal rotation of the flexed right hip (obturator sign) suggests the appendix is located:
Explanation. The obturator sign tests for irritation of the obturator internus muscle. A pelvic (low-lying) appendix positioned near the obturator internus will be irritated by rotation of the hip. The psoas sign (pain with right hip extension) suggests a retrocecal appendix lying on the right psoas major. Knowing the anatomical position explains atypical presentations.
3. A 45-year-old woman has a 5-day history of RLQ pain that has improved. CT shows a pericecal abscess 5cm, no free air or peritonitis. The optimal management is:
Explanation. Perforated appendicitis with a contained abscess (not free peritonitis) is managed with CT-guided drainage + IV antibiotics in the acute phase. Immediate surgery has higher complication rates. After resolution of the abscess (4–6 weeks), interval appendectomy is performed to prevent recurrence (~15–20% recurrence without surgery) and to exclude malignancy as the underlying cause.
Frequently asked questions
Why does appendicitis pain migrate from periumbilical to RLQ?expand_more
Early appendicitis causes visceral pain (from distension of the appendix) transmitted via T8–T10 visceral afferents — perceived as dull, colicky, periumbilical pain (visceral pain is poorly localized and referred to the periumbilical region for mid-gut structures). As inflammation progresses to involve the parietal peritoneum overlying the appendix (which is richly innervated by somatic sensory nerves), pain becomes sharp, well-localized, and constant at McBurney's point in the RLQ. This migration of pain is the classic diagnostic clue.
Is CT scan safe in children with suspected appendicitis?expand_more
The increased radiation exposure from CT raises theoretical lifetime cancer risk in children — cumulative pediatric CT exposure is a real concern. Current practice: start with graded-compression ultrasound in children. If ultrasound is diagnostic (appendix >6mm, non-compressible) → proceed. If ultrasound is non-diagnostic → MRI (preferred over CT in many children's hospitals) or CT if MRI unavailable/delayed. CT reserved for cases where ultrasound/MRI unavailable or equivocal and clinical urgency requires definitive imaging. Shared decision between surgeon, radiologist, and family.
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