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

Obtain CT abdomen/pelvis with IV contrast—this is the gold standard with sensitivity 96-100% and specificity 93-95%. 1, 2, 5

• Use IV contrast only; oral contrast is unnecessary and delays diagnosis 2
• For adolescents and young adults, use low-dose CT protocols to reduce radiation exposure 1, 2
• Point-of-care ultrasound (POCUS) by experienced emergency physicians or surgeons is an acceptable first-line alternative with sensitivity 91% and specificity 97% 1, 2

Children and Adolescents

Start with ultrasound as the first-line imaging modality (sensitivity 76%, specificity 95%) to avoid radiation exposure. 1, 2, 5

• If ultrasound is equivocal or non-diagnostic and clinical suspicion persists, proceed to MRI or low-dose CT 1, 2
• In children, combine imaging with clinical scores: fever >38°C, rebound tenderness, and WBC ≥10,100/mm³ creates a prediction rule with only 1% missed appendicitis rate 2
• Absent or decreased bowel sounds, positive psoas sign, positive obturator sign, and positive Rovsing sign are most reliable for ruling in appendicitis in children 2, 4

Pregnant Patients

Perform pregnancy testing first, then obtain ultrasound as initial imaging. 1, 5

• If ultrasound is inconclusive, proceed to MRI without IV contrast (sensitivity 94%, specificity 96%) rather than CT to avoid ionizing radiation 1, 2, 5
• First-trimester patients should never receive CT; use ultrasound followed by MRI if needed 1, 5

Elderly Patients (>40 years)

Obtain CT scan with IV contrast in all elderly patients due to higher rates of complicated appendicitis, atypical presentations, and increased mortality. 1, 2

CT Findings Indicating Complicated Appendicitis

Look for these high-risk features on CT that predict treatment failure with antibiotics and necessitate surgery: 2, 3

• Appendiceal diameter ≥13 mm
• Appendicolith (fecalith in appendiceal lumen)
• Extraluminal air
• Abscess formation
• Appendiceal wall enhancement defect
• Periappendiceal fat stranding

Management After Imaging

If imaging is negative but clinical suspicion remains high, obtain follow-up within 24 hours to ensure resolution of symptoms due to the low but measurable risk of false-negative results. 1, 5

If imaging shows complicated appendicitis with large periappendiceal abscess or phlegmon, consider percutaneous drainage plus antibiotics rather than immediate appendectomy. 5, 6

Treatment

Antibiotic Therapy

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

Antibiotic Regimens for Uncomplicated Appendicitis

• Second- or third-generation cephalosporins: cefoxitin or cefotetan 1
• Alternative: piperacillin-tazobactam monotherapy 7, 3
• Alternative: fluoroquinolone plus metronidazole 3

Antibiotic Regimens for Complicated/Perforated Appendicitis

Use piperacillin-tazobactam 3.375 grams IV every 6 hours (total 13.5 grams daily) for 7-10 days. 1, 7

Alternative regimens: 1

• Ampicillin-sulbactam
• Ticarcillin-clavulanate
• Imipenem-cilastatin
• Ampicillin + clindamycin (or metronidazole) + gentamicin
• Ceftriaxone + metronidazole

Do not add metronidazole when using broad-spectrum agents like aminopenicillins with β-lactam inhibitors or carbapenems, as anaerobic coverage is already provided. 1

Surgical Management

Perform appendectomy as soon as reasonably feasible once diagnosis is established—both laparoscopic and open approaches are acceptable, with laparoscopic preferred in children. 5, 8

• For uncomplicated appendicitis: Surgery within 24 hours of admission 5
• For complicated appendicitis: Early appendectomy within 8 hours is recommended 5
• Laparoscopic appendectomy is preferred over open due to reduced wound infections and faster recovery 5, 8

Postoperative Antibiotic Duration

For uncomplicated appendicitis: No postoperative antibiotics are needed beyond the preoperative dose. 1, 5

For complicated appendicitis in adults: Continue antibiotics for 4-7 days postoperatively. 1, 8

For complicated appendicitis in children: Switch to oral antibiotics after 48 hours with total duration less than 7 days. 1

Non-Operative Management Consideration

In highly selected patients with uncomplicated appendicitis AND no appendicolith on imaging, antibiotics-first strategy can be discussed as an alternative to surgery, with approximately 70% success rate at one year. 3, 9

However, recognize these critical limitations: 3, 9

• 30.7% of antibiotic-treated patients require appendectomy within one year
• CT findings of appendicolith, mass effect, or appendiceal diameter >13 mm predict 40% treatment failure with antibiotics
• Antibiotics increase negative appendectomy rates 3-fold if surgery becomes necessary later (RR 3.16)

Therefore, recommend surgical management in patients with CT findings of appendicolith, mass effect, or dilated appendix >13 mm who are fit for surgery. 3

Reserve antibiotics-first approach for unfit surgical candidates without high-risk CT findings. 3

Special Populations Requiring Urgent Surgery

Pregnant patients and immunosuppressed patients should undergo timely surgical intervention regardless of imaging findings to decrease risk of complications. 6

Common Pitfalls and Caveats

• Never rely solely on clinical findings without imaging in intermediate-risk patients—this leads to missed diagnoses or unnecessary surgeries 5
• Never delay antibiotics in confirmed or strongly suspected cases—this increases complication risk 5
• Never use clinical scores alone to confirm appendicitis—they help exclude disease but lack specificity for confirmation 1, 2
• Ultrasound accuracy is highly operator-dependent—both MRI and ultrasound may incorrectly classify up to half of perforated appendicitis cases as simple appendicitis 2
• In elderly patients, never skip CT imaging—atypical presentations are common and mortality is higher 1, 2
• Always obtain routine histopathology after appendectomy—this identifies unexpected findings including rare malignancies (0.3% incidence in antibiotic-treated patients) 5, 9
• For patients with persistent symptoms after 4-7 days of antibiotic therapy, obtain CT or ultrasound imaging to investigate treatment failure and consider extra-abdominal sources or noninfectious conditions 1