What is the standard approach to diagnosing and treating suspected appendicitis?

Standard Approach to Diagnosing and Treating Suspected Appendicitis

Diagnostic Algorithm

The diagnosis of appendicitis requires a systematic approach starting with clinical assessment using validated scoring systems, followed by imaging with CT scan (IV contrast) in non-pregnant adults, ultrasound in children and pregnant patients, and immediate broad-spectrum antibiotics once diagnosis is confirmed, followed by timely appendectomy. 1

Initial Clinical Assessment

• Identify the classic triad: periumbilical pain migrating to right lower quadrant, anorexia/nausea/vomiting, and localized right lower quadrant tenderness 2, 3
• Apply validated risk stratification scores (Alvarado, AIR, or AAS) to categorize patients as low, intermediate, or high-risk 1, 3
• Check for fever and positive psoas sign, which increase likelihood of appendicitis 4
• Note that vomiting before pain onset makes appendicitis less likely 4

Critical caveat: Low Alvarado scores do not reliably exclude appendicitis—8.4% of patients with appendicitis had scores below 5, and one study found 72% of patients with very low scores (1-4) ultimately had appendicitis 4. Therefore, proceed with imaging in intermediate-risk patients rather than relying solely on clinical scores.

Imaging Selection by Patient Population

Non-Pregnant Adults

• Obtain CT abdomen/pelvis with IV contrast as first-line imaging 1
• CT achieves 96-100% sensitivity and 93-95% specificity 4
• IV contrast improves sensitivity to 96% compared to unenhanced CT 4
• Oral contrast is unnecessary and delays diagnosis 4
• High-risk patients younger than 40 years (AIR score 9-12, Alvarado 9-10, AAS ≥16) may proceed directly to surgery without pre-operative imaging 1

Children and Adolescents

• Start with ultrasound as initial imaging modality 1
• Ultrasound has 76% sensitivity and 95% specificity in children 4
• Point-of-care ultrasound (POCUS) by emergency physicians/surgeons shows higher accuracy: 91% sensitivity, 97% specificity 4, 5
• Key ultrasound findings: appendiceal diameter ≥7 mm, non-compressibility, appendiceal tenderness on probe pressure 5
• If ultrasound is inconclusive, proceed to contrast-enhanced low-dose CT rather than standard-dose CT 1

Pregnant Patients

• Begin with ultrasound; if inconclusive, use MRI without IV contrast 1, 4
• MRI has 94% sensitivity and 96% specificity 4
• Avoid CT due to radiation exposure to fetus 1
• Laparoscopy or limited CT may be considered if ultrasound and MRI remain inconclusive 1

Management After Imaging

If Imaging Confirms Appendicitis

• Administer broad-spectrum antibiotics immediately covering gram-negative aerobes and anaerobes 1
• Appropriate regimens: piperacillin-tazobactam monotherapy, or cephalosporin/fluoroquinolone plus metronidazole 2
• Perform appendectomy (laparoscopic or open) as soon as reasonably feasible 1
• Both laparoscopic and open approaches are acceptable; choice depends on surgeon expertise 1

If Imaging Shows Complicated Appendicitis

• CT findings indicating complicated disease: extraluminal appendicolith, abscess, extraluminal air, appendiceal wall enhancement defect, periappendiceal fat stranding 4
• Proceed with urgent surgical intervention for source control 4
• Large periappendiceal abscess or phlegmon may warrant percutaneous drainage rather than immediate appendectomy 4, 6

If Imaging is Negative but Clinical Suspicion Persists

• Consider observation with supportive care, with or without antibiotics 1
• If clinical suspicion remains high despite negative imaging, consider surgical intervention 1
• Mandatory 24-hour follow-up if discharged, due to measurable false-negative rate 1

If Imaging is Inconclusive

• Initiate antimicrobial therapy along with pain medication and antipyretics 1
• For adults, provide antibiotics for minimum 3 days until symptoms resolve or definitive diagnosis is made 1
• Hospitalize if index of suspicion is high 1
• Consider cross-sectional imaging before surgery for patients with normal investigations but non-resolving right iliac fossa pain 1

Non-Operative Management Considerations

Antibiotics-first strategy can be discussed as an alternative to surgery in selected patients with uncomplicated appendicitis without appendicolith 1, though this requires careful patient counseling about failure rates.

• Success rate approximately 70% at initial treatment, but only 63-73% remain symptom-free at one year 2, 7
• CT findings predicting antibiotic failure (≈40% failure rate): appendicolith, mass effect, dilated appendix >13 mm 2
• Surgical management should be recommended in patients with these high-risk CT findings who are fit for surgery 2
• In unfit surgical candidates without high-risk findings, antibiotics-first approach is reasonable 2

Common Pitfalls to Avoid

• Do not administer analgesics before completing diagnostic evaluation, as this may mask evolving peritoneal signs 8
• Do not proceed directly to appendectomy without imaging in patients with incomplete clinical findings, as this risks unnecessary surgery (negative appendectomy carries long-term morbidity) and missing alternative diagnoses 4
• Do not rely solely on ultrasound to exclude appendicitis—it is better at confirming disease when positive than excluding it when negative 5
• Ultrasound accuracy is highly operator-dependent; both ultrasound and MRI may incorrectly classify up to half of perforated appendicitis cases as simple appendicitis 4
• Do not delay antibiotics in confirmed or strongly suspected cases, as this increases complication risk 8

Special Population Considerations

• Elderly patients: CT with IV contrast is strongly recommended due to higher rates of complicated appendicitis and mortality 4
• Pregnant and immunosuppressed patients: Proceed with timely surgical intervention to decrease complication risk 6
• Children aged <3 years: Imaging is particularly important when diagnosis is uncertain 1