Diagnostic and Treatment Approach for Suspected Appendicitis
Initial Clinical Assessment
Begin with focused evaluation for right lower quadrant pain with periumbilical migration, fever, and peritoneal signs—these findings combined with elevated WBC >10,000/mm³ AND CRP ≥8 mg/L have a positive likelihood ratio of 23.32 for appendicitis. 1
Key Clinical Findings to Assess
- Migration of pain from periumbilical region to right lower quadrant (highly predictive) 1
- Fever >38°C 1
- Peritoneal signs: rebound tenderness, guarding, rigidity 1
- Psoas sign and obturator sign (increase likelihood of appendicitis) 1
- Rovsing sign (pain in RLQ with palpation of LLQ) 1
Critical pitfall: Vomiting before pain onset makes appendicitis less likely—the typical sequence is pain first, then nausea/vomiting. 1
Laboratory Testing
Obtain WBC with differential and CRP in all patients. 1
- WBC >10,000/mm³ alone has limited value (LR+ only 1.59-2.7) 1
- CRP ≥10 mg/L has LR+ of 4.24 1
- The combination of WBC >10,000/mm³ AND CRP ≥8 mg/L is most powerful (LR+ 23.32, LR- 0.03) 1
Risk Stratification Using Clinical Scores
Use the AIR (Appendicitis Inflammatory Response) or AAS (Adult Appendicitis Score) in adults—these are the best-performing clinical prediction tools. 1 The Alvarado score should NOT be used alone to confirm appendicitis due to insufficient specificity, though it helps exclude the diagnosis. 1
In pediatric patients, use the Pediatric Appendicitis Score to exclude appendicitis, but never make the diagnosis based on clinical scores alone. 1
Imaging Strategy: Population-Specific Approach
Non-Pregnant Adults
Order CT abdomen/pelvis with IV contrast only—this is the gold standard with sensitivity 96-100% and specificity 93-95%. 1, 2, 3
Technical specifications:
- IV contrast alone is sufficient—oral contrast is NOT necessary and delays diagnosis by 40 minutes to 2+ hours without improving accuracy 3
- IV contrast increases sensitivity to 96% compared to 91% for unenhanced CT 3
- Oral contrast approximately doubles radiation exposure without benefit 3
When to proceed directly to surgery without imaging: Only in patients with very high clinical suspicion (high AIR/AAS score, classic presentation with peritoneal signs). 1 However, do NOT proceed to appendectomy without imaging in patients with incomplete clinical findings—this risks unnecessary surgery (negative appendectomy carries long-term morbidity) and missing alternative diagnoses. 1, 2
Children and Adolescents
Start with ultrasound as first-line imaging (sensitivity 76%, specificity 95%) to avoid radiation exposure. 1, 2, 3
Point-of-care ultrasound (POCUS) performed by emergency physicians or surgeons shows even higher accuracy: sensitivity 91%, specificity 97%. 1
Key ultrasound findings:
- Appendiceal diameter ≥7 mm 1
- Non-compressibility of appendix 1
- Appendiceal tenderness during examination 1
If ultrasound is equivocal or non-diagnostic and clinical suspicion persists, obtain CT abdomen/pelvis with IV contrast or MRI. 1, 2
Critical pitfall: Ultrasound accuracy is highly operator-dependent. 1
Pregnant Patients
Obtain ultrasound as initial imaging modality. 1, 2, 3
If ultrasound is inconclusive, proceed to MRI without IV contrast (sensitivity 94%, specificity 96%)—NOT CT, to avoid radiation. 1, 2, 3
Important caveat: Peritoneal signs may be less reliable in pregnancy due to anatomic displacement of the appendix. 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
Concerns about radiation exposure should be balanced against the need for accurate and timely diagnosis, especially given higher complication risk. 1
Management After Imaging
If Imaging Confirms Appendicitis
Initiate broad-spectrum antibiotics immediately covering aerobic gram-negative organisms and anaerobes (e.g., piperacillin-tazobactam monotherapy, or cephalosporin/fluoroquinolone + metronidazole). 1, 2, 4
Perform appendectomy as soon as reasonably feasible—both laparoscopic and open approaches are acceptable, with laparoscopic preferred in children. 1, 2
Special populations requiring timely surgical intervention:
- Pregnant patients (to decrease complications) 2, 5
- Immunocompromised patients 2, 5
- Patients with complicated appendicitis (perforation, abscess, phlegmon) 1
Non-Operative Management Consideration
In highly selected patients with uncomplicated appendicitis and NO appendicolith on imaging, an antibiotics-first strategy can be discussed as an alternative to surgery, with success rate of 63-73% at one year. 1, 4
CT findings predicting antibiotic failure (≈40% failure rate):
If these high-risk CT findings are present, recommend surgical management in patients fit for surgery. 4
If Imaging Shows Complicated Appendicitis
Urgent surgical intervention is required for source control. 1
Large periappendiceal abscess or phlegmon may warrant percutaneous drainage rather than immediate appendectomy. 1, 5
If Imaging is Negative but Clinical Suspicion Remains High
Consider observation with supportive care, with or without antibiotics, OR surgical intervention if clinical suspicion is very high despite negative imaging. 1, 3
Ensure follow-up within 24 hours if discharged. 1
Critical principle: Do not dismiss appendicitis based on negative imaging alone if clinical suspicion remains high—both MRI and ultrasound may incorrectly classify up to half of all patients with perforated appendicitis as having simple appendicitis. 1
Algorithm Summary by Clinical Suspicion Level
Very Low Clinical Suspicion
Intermediate Clinical Suspicion
- Adults: CT abdomen/pelvis with IV contrast 1, 2, 3
- Children: Ultrasound first, CT if equivocal 1, 2
- Pregnant: Ultrasound first, MRI if equivocal 1, 2