emDOCs Podcast – Episode 139: EBM Acute Appendicitis in Adults Part 2

What imaging is recommended?

• Several imaging tests available for diagnosis. X-ray has poor sensitivity and specificity. Other options include CT, ultrasound, MRI.
• The American College of Radiology (ACR) Appropriateness Criteria:
  • CT abdomen and pelvis with intravenous (IV) contrast is the recommended initial imaging for patients with RLQ pain, fever, and leukocytosis in the context of suspected appendicitis.
  • CT is usually appropriate for patients with isolated RLQ pain (37).
  • In those with RLQ with or without fever and leukocytosis, CT abdomen and pelvis without contrast, US, and MRI may also be appropriate (37).
  • In pregnant women with suspected appendicitis, US abdomen or MRI abdomen and pelvis without IV contrast is usually appropriate, while US pelvis, CT abdomen and pelvis with IV contrast, and CT abdomen and pelvis without contrast may be appropriate (37).
  • ACR recommendations are based on the high sensitivity, specificity, and diagnostic yield of CT for appendicitis and other conditions that may need surgical intervention.
• The Society of American Gastrointestinal and Endoscopic Surgeons (SAGE) guidelines state that US is a reasonable first line study due to its low cost and lack of radiation, but CT and MRI are the most definitive modalities (10).
• CT is a reliable imaging modality.
  • Meta-analysis data demonstrate sensitivity of 96% and specificity over 93% for CT with IV contrast (38).
  • CT without contrast accurate: systematic review of 7 studies found CT without contrast had a sensitivity of 92.7% and specificity 96.1% (39). 2019 Cochrane review found CT without IV contrast had a sensitivity of 91% and specificity of 93% (38).
  • Data suggest oral and rectal contrast do not improve diagnostic yield (38,40,41). Cochrane review found a sensitivity of 89% for CT with oral contrast (38).
  • Low-radiation protocols use 2-4 mSv versus the standard 8-10 mSv) (38,42).
    • A single-center study evaluating 879 patients found no difference with low-dose versus standard-dose CT groups in sensitivity and specificity (42).
    • OPTICAP trial found a low-dose protocol with IV contrast was not inferior for diagnostic accuracy compared to standard-dose protocol
    • Cochrane review found similar sensitivity and specificity for low-dose and standard-dose CT (94% versus 95%) (38).
  • CT findings: enlarged appendix (≥ 8-9 mm outer-to-outer diameter) with occluded lumen, periappendiceal fat stranding, wall thickening (> 3 mm), wall enhancement, and appendicolith (Figure 1) (37,44,45).

• Graded compression US has been evaluated in adults and is the first-line modality in pregnant women
  • Sensitivity 21-96% and specificity 71-98% (46-57).
  • Rates of non-visualization vary between 34-71%; indeterminate rates may reach 85% (52,53,58-60).
  • Standardized results reporting improves US reliability for diagnosing of appendicitis (60).
  • US is more likely to visualize the appendix in men, BMI < 22 mg/kg², and more severe pain (50,52). Y
  • US findings: noncompressible appendix with wall thickness > 6 mm, pain over the appendix with compression, hyperechoic appendicolith, increased echogenicity of periappendiceal fat, and fluid in the RLQ (Figure 2) (46-57).

• MRI is a third-line imaging modality
  • This test is mostly used in pregnant women if US is unavailable or equivocal; MRI can also be used as a first-line imaging modality if available (61,62).
  • Sensitivity is 85-98% and specificity is 97-99% for experienced radiologists; lower in less experienced readers (77-89% and 79-83%, respectively) (63-69).
  • Non-diagnostic rate ranges between 20-40% (63-69).
  • In pregnant patients, sensitivity ranges between 89-100% and specificity 93-99% (70-75).
  • Imaging time is longer with MRI.
  • MRI findings: fluid-filled, enlarged appendix (>7 mm) (Figure 3).

• Guidelines:
  • See ACR discussion above (CT with IV contrast first-line imaging modality in adults with RLQ abdominal pain or for suspected appendicitis).
  • WSES recommends using clinician pre-image likelihood of appendicitis in conjunction with scoring systems (3,37). In intermediate risk patients based on AIR/AAS/Alvarado score, US can used as a first-line imaging test. If the patient has persisting pain in the RLQ, obtain cross-sectional imaging like CT; use low-dose CT with IV contrast in those with suspected appendicitis when clinically appropriate. For MRI, the WSES guidelines state that while it is sensitive and specific for appendicitis during pregnancy, a negative or inconclusive MRI should not be used to exclude the diagnosis if there’s high clinical suspicion (3). In patients with concern for complicated appendicitis (perforation, phlegmon, abscess), or in elderly patients, obtain CT with IV contrast.
• Summary: Based on the available data and guidelines, several imaging modalities are available. In well-appearing, US can be used as a first-line imaging test. If US is unable to visualize the appendix or if the patient has evidence of sepsis, is elderly, or is critically ill, obtain CT, preferably with IV contrast, but oral contrast is not routinely needed. For pregnant patients, use US and MRI if possible.

What is the management?

• Consult surgery for all patients with acute appendicitis and administer IV antibiotics (76).
  • Operative intervention necessary for patients with critical illness or those with emergent intervention.
  • Stable patients with a perforation with phlegmon or abscess can be managed with IV antibiotics and image-guided drainage; early appendectomy is associated with worse outcomes in these patients (3,9). If the patient does not improve, appendectomy is needed (77).
• Previously all patients with appendicitis were treated with surgery and antibiotics, but nonoperative management with antibiotics alone in appropriately selected patients has literature support.
• Nonoperative management with antibiotics alone only for those with uncomplicated appendicitis; defined as those without abscess, appendiceal gangrene, perforation, sepsis, or hemodynamic instability (78-87).
  • 2025 meta-analysis included six trials with 2101 participants published between 2011 to 2021 (1050 received antibiotics and 1051 underwent appendectomy). Within one year, 57 (5.4%) of the 1050 patients receiving non-operative management with antibiotics alone experienced a complication, versus 87 (8.3%) of the 1051 patients receiving appendectomy (OR 0.49; 95% CI 0.20 to 1.20) (87). At one year, 33.9% of the antibiotics alone group had undergone appendectomy. Those with appendicolith at preinterventional imaging undergoing nonoperative management had a higher rate of complications versus appendectomy (15.0% versus 6.3%; OR 2.82; 95% CI 1.11 to 7.18; risk difference 13.2%; 95% CI 2.3% to 24.2%). In patients randomized to antibiotics alone, 94 (48.7%) of 193 patients with an appendicolith underwent appendectomy within one year, compared with 262 (30.6%) of 857 patients without an appendicolith (87).
  • Several guidelines support non-operative management with antibiotics in uncomplicated appendicitis: the Journal of Trauma and Acute Care Surgery Emergency General Surgery Work Group, American Association for the Surgery of Trauma (AAST), and WSES (3,9,88).
    • The Eastern Association for the Surgery of Trauma does not make a recommendation for or against non-operative management with antibiotics-first versus surgery for acute uncomplicated appendicitis due to what they state are limitations in the current data (89).
    • The 2024 SAGE guidelines recommend that patients with either uncomplicated or complicated appendicitis be managed operatively and not nonoperatively (10).
    • The WSES recommends nonoperative management in uncomplicated appendicitis without appendicolith.
    • The AAST states that a fecalith does not preclude nonoperative management, but there is a higher probability of requiring additional procedures (3,88).
  • Consideration: most current literature used CT for diagnosis and to confirm uncomplicated appendicitis, and the studies used IV antibiotics for several days while the patient was admitted, followed by oral antibiotics for 7-10 days (3,90).
  • The APPAC II trial included 583 patients with uncomplicated appendicitis and compared moxifloxacin 400 mg per os (PO) for 7 days versus ertapenem 1 g IV followed by levofloxacin 500 mg PO with metronidazole 500 mg PO three times per day for 5 days (91). Seven days of oral moxifloxacin failed to demonstrate non-inferiority. Secondary analysis found a slightly higher appendectomy rate in those who received oral antibiotic monotherapy, and noninferiority could not be demonstrated (92).
  • 2025 nested trial randomized patients with appendicitis but no perforation waiting for surgery to either receive antibiotics or not receive them until induction in the OR (93). Authors found similar rates of perforation (8.3% versus 8.9%; difference 0.6%; 95% CI -2 to 3.2). For the secondary outcome, lower rate of surgical site infection rate in the antibiotic group (14 of 887 [1.6%]) versus the no-antibiotic group (28 of 886 [3.2%]; absolute difference 1.6 percentage points; 95% CI 0.2 to 3.0) (93).
• For antibiotics, guidelines recommend using IV antibiotics initially, followed by transition to oral antibiotics based on the individual patient condition (3,9).

• Summary: Based on current evidence and guidelines, consult surgery and administer antibiotics for appendicitis. Non-operative management with antibiotics alone may be safe in select patients with uncomplicated appendicitis, particularly those without appendicolith.
• Caveats: Shared decision making is essential if using nonoperative management discussing possibility of failure and risk of complications (3). Non-operative management with antibiotics alone is not recommended in pregnant patients or elderly patients who are appropriate for surgery (3,94).

Key Take homes:

• RLQ pain or tenderness, migrating pain, Rovsing’s sign, psoas sign, and obturator sign are suggestive of the diagnosis; no single finding in isolation can rule in or rule out the diagnosis.
• Combination of normal WBC, normal neutrophil distribution, and normal CRP suggest appendicitis is less likely.
• Current evidence demonstrates the highest diagnostic accuracy with AIR, AAS, and RIPASA.
• US or CT with IV contrast may be appropriate for the first-line imaging modality in adults, but use CT with IV contrast if concerned about a complication. For pregnancy, US and MRI are the recommended imaging tests.
• For treatment, consult surgery and administer antibiotics. Non-operative management with antibiotics alone may be safe in select patients with uncomplicated appendicitis with shared decision-making.

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