What is the appropriate diagnosis and treatment for a patient with suspected appendicitis?

Diagnosis and Management of Appendicitis

Diagnostic Approach

For adults with suspected appendicitis, begin with clinical risk stratification using validated scoring systems (AIR or AAS scores), followed by CT abdomen/pelvis with IV contrast as the primary imaging modality, then proceed to urgent appendectomy with broad-spectrum antibiotics covering gram-negative organisms and anaerobes. 1, 2

Initial Clinical Assessment

• Assess for characteristic findings: periumbilical pain migrating to the right lower quadrant, anorexia, nausea/vomiting, localized right lower quadrant tenderness, and fever 1, 3
• Right lower quadrant pain, abdominal rigidity, and periumbilical pain radiating to the right lower quadrant are the most reliable signs for ruling in appendicitis in adults 4
• Positive psoas sign, fever, or migratory pain to the right lower quadrant increases likelihood of appendicitis; vomiting before pain makes it less likely 2
• Obtain WBC with differential and CRP in all patients—WBC >10,000/mm³ AND CRP ≥8 mg/L has a positive likelihood ratio of 23.32 2

Risk Stratification Using Clinical Scores

Apply the AIR score (0-12 points) or AAS score to stratify patients into low, intermediate, or high-risk categories before proceeding with imaging. 1, 2

• Low-risk patients (AIR score <5): Consider discharge with 24-hour follow-up or observation without immediate imaging 1, 2
• Intermediate-risk patients (AIR score 5-8): Proceed with diagnostic imaging—these patients benefit most from systematic imaging 1, 2
• High-risk patients (AIR score 9-12) under age 40: May proceed directly to surgery without preoperative imaging, though imaging is still recommended in most cases 1, 2

Do NOT use the Alvarado score alone to confirm appendicitis in adults due to insufficient specificity, though it helps exclude the diagnosis. 2 Studies show 8.4% of patients with appendicitis had Alvarado scores below 5, and one study found 72% with very low scores (1-4) ultimately had appendicitis. 2

Imaging Strategy by Patient Population

Non-Pregnant Adults

CT abdomen and pelvis with IV contrast is the recommended first-line imaging modality, with sensitivity 96-100% and specificity 93-95%. 1, 2

• Use IV contrast only—oral contrast is unnecessary and delays diagnosis 2
• Consider low-dose CT protocols in adolescents and young adults to reduce radiation exposure 1, 2
• If CT is negative but clinical suspicion persists, obtain cross-sectional imaging before surgery or consider exploratory laparoscopy 1

Children and Adolescents

Ultrasound is the first-line imaging modality (sensitivity 76%, specificity 95%) to avoid radiation exposure. 1, 2

• Key ultrasound findings: appendiceal diameter ≥7 mm, non-compressibility, appendiceal tenderness 2
• Point-of-care ultrasound (POCUS) by emergency physicians or surgeons shows higher accuracy (sensitivity 91%, specificity 97%) 1, 2
• If ultrasound is equivocal and clinical suspicion persists, proceed to MRI or low-dose CT 1
• In children, combine ultrasound with clinical scores (Pediatric Appendicitis Score) to improve diagnostic accuracy—never diagnose based on scores alone 1, 2

Pregnant Patients

All female patients of childbearing potential require pregnancy testing before imaging. 1

• First-line: Ultrasound with graded compression 1, 2
• If ultrasound inconclusive: MRI without IV contrast (sensitivity 94%, specificity 96%) is preferred over CT to avoid ionizing radiation 1, 2
• If MRI is negative but clinical suspicion remains high, consider laparoscopy or limited CT scanning 1

Elderly Patients (>40 years)

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

• Atypical presentations are common in elderly patients—do not rely on clinical findings alone 2

CT Findings Indicating Complicated Appendicitis

CT findings suggesting complicated disease include: 1, 2

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

Follow-Up After Negative Imaging

For patients with negative imaging but non-resolving symptoms, follow-up at 24 hours is mandatory due to the low but measurable risk of false-negative results. 1

• If symptoms persist or progress despite negative imaging, obtain repeat cross-sectional imaging or proceed to exploratory laparoscopy 1

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Treatment

Antibiotic Therapy

Administer broad-spectrum antibiotics immediately once appendicitis is diagnosed or strongly suspected, covering aerobic gram-negative organisms (E. coli) and anaerobes (Bacteroides species). 1, 5, 3

Antibiotic Regimens for Uncomplicated Appendicitis

• Preferred: Piperacillin-tazobactam 3.375 grams IV every 6 hours 1, 6, 3
• Alternatives: Second- or third-generation cephalosporins (cefoxitin or cefotetan) 1

Antibiotic Regimens for Complicated Appendicitis

• Preferred: Piperacillin-tazobactam 4.5 grams IV every 6 hours 1, 6
• Alternatives: Ampicillin-sulbactam, ticarcillin-clavulanate, imipenem-cilastatin, or combination therapy with ampicillin + clindamycin (or metronidazole) + gentamicin 1
• Metronidazole is not needed when using broad-spectrum agents like aminopenicillins with β-lactam inhibitors or carbapenems 1

Surgical Management

Appendectomy (laparoscopic or open) remains the standard of care and should be performed as soon as reasonably feasible once diagnosis is established. 5, 3, 7

Timing of Surgery

• Uncomplicated appendicitis: Surgery within 24 hours of admission 5
• Complicated appendicitis: Early appendectomy within 8 hours is recommended 5
• Laparoscopic appendectomy is preferred in children 5

Surgical Approach for Complicated Disease

• Perforated appendicitis: Urgent surgical intervention for source control 5
• Large periappendiceal abscess or phlegmon: Consider percutaneous drainage plus antibiotics rather than immediate appendectomy 5

Postoperative Antibiotic Management

Uncomplicated Appendicitis

No postoperative antibiotics are needed after appendectomy for uncomplicated appendicitis in both adults and children. 1

Complicated Appendicitis

Continue antibiotics postoperatively for complicated appendicitis, with early switch to oral antibiotics after 48 hours and total duration shorter than 7 days. 1

• In children with complicated appendicitis, early transition to oral antibiotics is safe, effective, and cost-efficient 1
• Postoperative antibiotics can be administered orally if the patient is well enough for discharge 1

Non-Operative Management (Antibiotics-First Strategy)

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, with a success rate of approximately 63-73% at one year. 5, 3, 8

Patient Selection for Non-Operative Management

• Appropriate candidates: Uncomplicated appendicitis without appendicolith, mass effect, or appendiceal diameter >13 mm on CT 3
• Poor candidates: Presence of appendicolith, mass effect, or dilated appendix >13 mm—these findings are associated with 40% treatment failure rate with antibiotics 3

Outcomes of Antibiotics-First Approach

• Approximately 30.7% of antibiotic-treated patients require appendectomy within one year, or conversely, more than two-thirds avoid surgery 8
• Antibiotics may reduce wound infections compared to surgery 8
• Antibiotics probably increase negative appendectomy rates if surgery is eventually required (RR 3.16) 8

Surgical management should be recommended in patients with CT findings of appendicolith, mass effect, or dilated appendix who are fit for surgery. 3

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Special Populations

Pregnant Patients

• Appendectomy should be performed promptly to reduce risk of perforation and maternal/fetal complications 9
• Laparoscopic approach is safe in pregnancy 9

Immunosuppressed Patients

• Timely surgical intervention is recommended to decrease risk of complications 9

Patients >40 Years with Complicated Appendicitis Treated Non-Operatively

These patients should undergo colonic screening and interval full-dose contrast-enhanced CT scan to exclude malignancy. 1

• The incidence of malignancy in the antibiotic group is 0.3%, though follow-up was variable 8

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Common Pitfalls and Caveats

• Relying solely on clinical scores without imaging: Clinical scores help stratify risk but should not be used alone to confirm or exclude appendicitis, especially in adults 1, 2
• Ultrasound accuracy is operator-dependent: Both MRI and ultrasound may incorrectly classify up to half of patients with perforated appendicitis as having simple appendicitis 2
• Delaying antibiotics: Antibiotics should be initiated immediately upon diagnosis or strong suspicion—delays increase complication risk 5
• Proceeding to surgery without imaging in intermediate-risk patients: This risks unnecessary surgery if appendicitis is absent and misses alternative diagnoses 2
• Ignoring persistent symptoms after negative imaging: False-negative imaging occurs—24-hour follow-up is mandatory, and repeat imaging or laparoscopy should be considered if symptoms persist 1
• Routine histopathology is recommended after appendectomy to identify unexpected findings, including rare malignancies 5