What is the recommended approach to a patient with suspected acute appendicitis?

Approach to Suspected Acute Appendicitis

Use a risk-stratified diagnostic pathway combining clinical scoring systems (AIR or AAS scores in adults, Pediatric Appendicitis Score in children) with tailored imaging—ultrasound first in children and pregnant patients, CT with IV contrast in non-pregnant adults with intermediate-to-high risk—to guide timely surgical or antibiotic management. 1, 2

Initial Clinical Assessment and Risk Stratification

Adults

• Apply the AIR (Appendicitis Inflammatory Response) score or AAS (Adult Appendicitis Score) as your primary clinical prediction tool—these have the highest discriminating power and effectively identify low-risk patients who can avoid imaging and hospital admission while flagging intermediate-risk patients who need diagnostic imaging 1
• Do NOT use the Alvarado score alone to confirm appendicitis in adults due to insufficient specificity, though it helps exclude the diagnosis 1
• Obtain WBC with differential and CRP in all patients—the combination of WBC >10,000/mm³ AND CRP ≥8 mg/L has a positive likelihood ratio of 23.32 2

Pediatric Patients

• Use the Alvarado score or Pediatric Appendicitis Score to exclude appendicitis, but never make the diagnosis based on clinical scores alone 1
• In children, CRP ≥10 mg/L and leukocytosis ≥16,000/mL are strong predictive factors 1
• The combination of fever >38°C, rebound tenderness, and WBC ≥10,100/mm³ creates a prediction rule with only 1% missed appendicitis rate 2

Key Physical Examination Findings

• In adults: right lower quadrant pain, abdominal rigidity, and periumbilical pain migrating to the right lower quadrant are the best signs for ruling in appendicitis 3
• In children: absent or decreased bowel sounds, positive psoas sign, positive obturator sign, and positive Rovsing sign are most reliable 3
• Critical pitfall: Do not rely on physical examination findings alone—they must be combined with laboratory findings and imaging to guide management decisions 2

Imaging Strategy Based on Patient Population

Non-Pregnant Adults

• CT abdomen and pelvis with IV contrast is the recommended initial imaging modality for intermediate-to-high clinical suspicion, with sensitivity 96-100% and specificity 93-95% 1, 2
• IV contrast increases sensitivity to 96% compared to unenhanced CT; oral contrast is generally not necessary and may delay diagnosis 1, 2
• In high-risk patients younger than 40 years old (AIR score 9-12, Alvarado score 9-10, AAS ≥16), you may proceed directly to surgery without cross-sectional imaging 1
• Use contrast-enhanced low-dose CT over standard-dose CT in adolescents and young adults to reduce radiation exposure 1

Children and Adolescents

• Ultrasound is the recommended initial imaging modality (sensitivity 76%, specificity 95%) to avoid radiation exposure 1, 2
• If ultrasound is equivocal or non-diagnostic and clinical suspicion persists, proceed to CT with IV contrast (sensitivity 96-100%, specificity 93-95%) or MRI without IV contrast (sensitivity 94%, specificity 96%) 1, 2
• Point-of-care ultrasound (POCUS) performed by emergency physicians or surgeons shows even higher accuracy (sensitivity 91%, specificity 97%) 1, 2

Pregnant Patients

• Ultrasound is the recommended initial imaging modality 1, 2
• If ultrasound is inconclusive, MRI without IV contrast is preferred over CT (sensitivity 94%, specificity 96%) to avoid radiation exposure 1, 2
• Do not make the diagnosis based on symptoms and signs alone—laboratory tests and inflammatory serum parameters (e.g., CRP) should always be requested 1
• Important caveat: A negative or inconclusive MRI does not exclude appendicitis; surgery should still be considered if high clinical suspicion persists 1

Elderly Patients

• CT scan with IV contrast is strongly recommended due to higher rates of complicated appendicitis and mortality in this population 1, 2

Ultrasound Technical Considerations

Key diagnostic findings on ultrasound include:

• Appendiceal diameter ≥7 mm 2, 4
• Non-compressibility of the appendix 2
• Appendiceal tenderness during examination 2

Major pitfall: Ultrasound accuracy is highly operator-dependent, and both MRI and ultrasound may incorrectly classify up to half of all patients with perforated appendicitis as having simple appendicitis 1, 2

CT Findings Indicating Complicated Appendicitis

CT findings suggestive of complicated disease include:

• Extraluminal appendicolith 1, 2
• Abscess formation 1, 2
• Extraluminal air 1, 2
• Appendiceal wall enhancement defect 1, 2
• Periappendiceal fat stranding 1, 2
• Appendiceal diameter >13 mm 4

Management After Imaging

Positive Imaging

• Administer broad-spectrum antibiotics immediately once appendicitis is diagnosed or strongly suspected—regimens should cover aerobic gram-negative organisms and anaerobes (e.g., piperacillin-tazobactam monotherapy or combination therapy with cephalosporins or fluoroquinolones plus metronidazole) 2, 4
• Appendectomy should be performed as soon as reasonably feasible once diagnosis is established 2
• Both laparoscopic and open appendectomy are acceptable, with laparoscopic approach preferred in children 2

Complicated Appendicitis with Large Abscess

• Large periappendiceal abscess or phlegmon may warrant percutaneous drainage rather than immediate appendectomy 2, 5

Negative or Inconclusive Imaging

• If imaging is negative but clinical suspicion remains high, consider observation and supportive care, with or without antibiotics 1
• If clinical suspicion is very high despite negative imaging, consider surgical intervention 1
• Ensure follow-up within 24 hours if discharged, because of the low but measurable risk of false-negative results 1
• For patients with normal investigations but non-resolving right iliac fossa pain, cross-sectional imaging is recommended before surgery; if imaging remains negative with progressive or persistent pain, exploratory laparoscopy is recommended 1

Non-Operative Management Consideration

• In highly selected patients with uncomplicated appendicitis and absence of appendicolith on imaging, an antibiotics-first strategy can be discussed as an alternative to surgery 2, 4
• Success rate is approximately 63-73% at one year, but approximately 37% of adult patients treated conservatively undergo appendectomy within one year 4, 6
• CT findings that predict higher failure rates (≈40%) of antibiotics-first approach: appendicolith, mass effect, or dilated appendix >13 mm 4
• Surgical management should be recommended in patients with these high-risk CT findings who are fit for surgery 4

Special Populations Requiring Surgical Intervention

• Pregnant patients and immunosuppressed patients should undergo timely surgical intervention to decrease the risk of complications 5

Common Pitfalls to Avoid

• Do not proceed directly to surgery without imaging in patients with incomplete clinical findings—this risks unnecessary surgery if appendicitis is absent (negative appendectomy carries long-term morbidity) and missing alternative diagnoses 2
• Do not dismiss low or incomplete Alvarado scores as excluding appendicitis—studies show 8.4% of patients with appendicitis had Alvarado scores below 5, and one study found 72% of patients with very low scores (1-4) ultimately had appendicitis 2
• Balance concerns about radiation exposure with the need for accurate and timely diagnosis, especially in elderly patients with higher risk of complications 1, 2
• Recognize that peritoneal signs may be less reliable in pregnant patients due to anatomic displacement 2