What is the recommended diagnostic and treatment approach for acute appendicitis, including imaging, antibiotics, and surgical versus non‑operative management?

Acute Appendicitis: Diagnostic and Treatment Approach

Diagnosis

Use a risk-stratified approach combining clinical scoring systems (AIR or Adult Appendicitis Score 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 enable timely surgical or antibiotic treatment. 1, 2

Clinical Risk Stratification

Adults:

• Apply the AIR (Appendicitis Inflammatory Response) score or Adult Appendicitis Score, which provide the highest discriminating power for identifying low-risk patients who can avoid imaging and admission versus intermediate-risk patients requiring diagnostic imaging 1, 2
• The Alvarado score alone lacks sufficient specificity in adults and should not be used to confirm appendicitis, though it helps exclude the diagnosis 1, 2
• 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

Children:

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

Imaging Strategy by Population

Non-Pregnant Adults (<40 years old):

• CT abdomen-pelvis with IV contrast is the recommended initial imaging for intermediate-to-high clinical suspicion, offering sensitivity of 96-100% and specificity of 93-95% 1, 2
• IV contrast raises sensitivity to approximately 96% compared with unenhanced CT; oral contrast is unnecessary and may delay diagnosis 1, 2
• Patients with high clinical scores (AIR 9-12, Alvarado 9-10) may proceed directly to surgery without cross-sectional imaging 1, 2
• For adolescents and young adults, use contrast-enhanced low-dose CT to limit radiation exposure 1, 2

Elderly Patients (≥40 years old):

• CT with IV contrast is strongly recommended because older adults have higher rates of complicated appendicitis and associated mortality 1, 2
• The benefit of accurate diagnosis outweighs radiation concerns in this population 2

Children and Adolescents:

• Ultrasound is the first-line imaging modality to avoid radiation, with sensitivity approximately 76% and specificity approximately 95% 1, 2, 3
• If ultrasound is equivocal or nondiagnostic and clinical suspicion persists, proceed directly to CT with IV contrast (sensitivity 96-100%, specificity 93-95%) rather than repeating ultrasound 2
• MRI without IV contrast is a radiation-free alternative (sensitivity 94%, specificity 96%) 1, 2
• Point-of-care ultrasound performed by emergency physicians or surgeons yields higher accuracy (sensitivity approximately 91%, specificity approximately 97%) 2
• Do not repeat ultrasound after an initial nondiagnostic study if clinical suspicion remains high 2

Pregnant Patients:

• Ultrasound remains the initial imaging choice 1, 2
• When ultrasound is inconclusive, MRI without IV contrast is preferred over CT, providing sensitivity approximately 94% and specificity approximately 96% while avoiding fetal radiation 1, 2
• A negative or inconclusive MRI does not rule out appendicitis; surgery should be considered if clinical suspicion remains high 2

CT Findings Indicating Complicated Appendicitis

• Extraluminal appendicolith, peri-appendiceal abscess, extraluminal air, wall enhancement defect, and peri-appendiceal fat stranding indicate complicated disease requiring urgent surgical intervention 1, 2

Management After Inconclusive Imaging

• If imaging is negative but clinical suspicion remains high, observe with supportive care and consider antibiotics; surgical intervention may be pursued if suspicion persists 2
• Ensure follow-up within 24 hours after discharge because of measurable risk of false-negative results 2
• For patients with normal investigations but persistent right iliac fossa pain, obtain cross-sectional imaging before surgery; if imaging remains negative and pain progresses, exploratory laparoscopy is recommended 2

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Treatment

Antibiotic Therapy

Preoperative Antibiotics:

• Administer a single preoperative dose of broad-spectrum antibiotics (from 0 to 60 minutes before surgical skin incision) in all patients with acute appendicitis undergoing appendectomy 1
• For uncomplicated cases, use second- or third-generation cephalosporins such as cefoxitin or cefotetan 1
• For complicated appendicitis, initiate intravenous antibiotics effective against enteric gram-negative organisms and anaerobes (E. coli and Bacteroides spp.) as soon as diagnosis is established 1
• Broader-spectrum coverage includes piperacillin-tazobactam, ampicillin-sulbactam, ticarcillin-clavulanate, or imipenem-cilastatin 1, 4

Postoperative Antibiotics:

Adults:

• Do not use postoperative antibiotics for uncomplicated appendicitis 1
• For complicated appendicitis with adequate source control, discontinue antibiotics after 3-5 days postoperatively; do not prolong beyond this duration 1
• Early switch to oral antibiotics (after 48 hours) is safe, effective, and cost-efficient 1

Children:

• Do not use postoperative antibiotics for uncomplicated appendicitis 1, 3
• For complicated appendicitis, switch to oral antibiotics after 48 hours with overall therapy duration shorter than 7 days 1, 3

Surgical Management

Adults:

• Laparoscopic appendectomy is the preferred approach, offering better outcomes than open surgery 1, 4
• Perform appendectomy as soon as reasonably feasible once diagnosis is established 1, 5
• For complicated appendicitis with phlegmon or abscess, laparoscopic appendectomy is treatment of choice where advanced laparoscopic expertise is available, with low threshold for conversion 1
• For large appendiceal abscess or phlegmon, consider percutaneous drainage plus antibiotics rather than immediate appendectomy 1, 5

Children:

• Laparoscopic appendectomy is the preferred treatment approach, offering better treatment success rates, lower recurrence rates, and improved quality of life compared to open surgery 3
• Perform surgery within 24 hours of admission for uncomplicated appendicitis 3
• For perforated appendicitis, early appendectomy within 8 hours is recommended 3
• Use conventional three-port laparoscopic appendectomy rather than single-incision approaches due to shorter operative times, less postoperative pain, and lower wound infection incidence 3
• Simple ligation of the appendicular stump is recommended over stump inversion, associated with shorter operative times and quicker recovery 3
• Do not use prophylactic abdominal drainage after laparoscopic appendectomy for complicated appendicitis, as it does not prevent complications and may be associated with negative outcomes 3

Non-Operative Management (Antibiotics-First Strategy)

Patient Selection for Antibiotics-First Approach:

Adults:

• Non-operative management with antibiotics can be considered in highly selected patients with uncomplicated appendicitis and absence of appendicolith on imaging 1, 4, 5
• Do not attempt antibiotic management if CT shows appendicolith, mass effect, or dilated appendix >13 mm, as these findings are associated with approximately 40% treatment failure rate 4
• Success rate of antibiotics-first strategy is approximately 63-73% at one year, meaning more than two-thirds avoid surgery 6, 7
• At one year, 30.7% of antibiotic-treated participants required appendectomy 6
• Use broad-spectrum antibiotics such as piperacillin-tazobactam monotherapy or combination therapy with cephalosporins or fluoroquinolones plus metronidazole 4

Children:

• Non-operative management with antibiotics can be discussed as an alternative to surgery in selected children with uncomplicated appendicitis in the absence of an appendicolith 3
• When choosing non-operative management, advise patients and families about the possibility of treatment failure and risk of misdiagnosing complicated appendicitis 3
• Initial intravenous antibiotics with subsequent conversion to oral antibiotics is recommended based on clinical condition 3

Critical Caveat:

• If appendicolith is present with acute appendicitis, surgical management is strongly preferred due to 47-60% failure rate of non-operative management 8

Interval Appendectomy

• Do not perform routine interval appendectomy after non-operative management for complicated appendicitis in young adults (<40 years old) and children 1
• Interval appendectomy is recommended only for patients with recurrent symptoms 1
• For patients ≥40 years old treated non-operatively, perform both colonic screening with colonoscopy and interval full-dose contrast-enhanced CT scan due to 3-17% incidence of appendicular neoplasms 1

Special Populations

Pregnant Patients:

• Perform surgery promptly if appendicitis is confirmed to decrease risk of complications 5

Immunosuppressed Patients:

• Undergo timely surgical intervention to decrease risk of complications 5

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Common Pitfalls

• Do not confuse incidental appendicolith (found on imaging without appendicitis) with appendicolith-associated appendicitis—management differs dramatically; observation without surgery is appropriate for incidental findings 8
• Ultrasound demonstrates low sensitivity (33.9-51.5%) for detecting perforated appendicitis, limiting its utility when perforation status influences management 2
• Non-visualization of the appendix on ultrasound does not exclude appendicitis; about 26% of patients with equivocal ultrasound ultimately have appendicitis 2
• Do not proceed directly to surgery without imaging in patients with incomplete clinical findings, as this risks unnecessary surgery if appendicitis is absent and misses alternative diagnoses 2
• Low or incomplete Alvarado scores do not reliably exclude appendicitis—studies show 8.4% of patients with appendicitis had scores below 5 2