Acute Appendicitis: Diagnosis, Appendectomy vs Antibiotics-First, and Complicated Disease

Conclusión

Initial workup

• CT confirms the diagnosis and classifies severity: uncomplicated appendicitis is an inflamed appendix without necrosis, perforation, abscess, or appendicolith, typically ≤ 1.1 cm in diameter. No further imaging is needed once CT is definitive.
• Baseline CBC, CMP, CRP, lactate if ill-appearing, coagulation studies if anticoagulated, type and screen, and urine hCG in patients of childbearing potential. CRP and WBC also inform candidacy for nonoperative management (CRP < 6 mg/dL and WBC < 12 × 10⁹/L predict success).
• Assess for peritonitis, immunosuppression, pregnancy, and symptom duration — each alters the operative-versus-nonoperative decision and its urgency.

Acute management

• NPO, IV isotonic fluids, analgesia (acetaminophen with or without an opioid; NSAIDs if not contraindicated), and antiemetics. Early surgical consultation — the treatment decision is surgical.
• Start IV antibiotics with gram-negative and anaerobic coverage at diagnosis: ceftriaxone 1–2 g IV daily plus metronidazole 500 mg IV every 8 hours, or cefoxitin 2 g IV every 6–8 hours. In beta-lactam allergy, ciprofloxacin 400 mg IV every 12 hours plus metronidazole.
• Recommend laparoscopic appendectomy as definitive therapy, performed within roughly 12–24 hours of diagnosis; overnight scheduling of a stable patient is acceptable.
• If the patient declines surgery or has prohibitive operative risk, nonoperative management is reasonable. An appendicolith-free appendix is the single most favorable predictor — an appendicolith raises antibiotic failure to about 46%. The most favorable profile is pain < 3 days, afebrile, WBC < 12–15 × 10⁹/L, and diameter < 1 cm; fever, higher WBC, or a larger appendix are relative cautions that favor surgery.
• Antibiotics-first regimen (APPAC-style): ertapenem 1 g IV daily for 3 days, then oral levofloxacin 500 mg daily plus metronidazole 500 mg three times daily for 4 days, with inpatient observation for 24–48 hours to confirm clinical response.

Inpatient and longitudinal management

• After appendectomy for uncomplicated appendicitis, no postoperative antibiotics are needed — stop after the perioperative dose. Advance diet as tolerated, mobilize, and transition to oral analgesia; most patients discharge the same day or within 24 hours.
• If pathology shows gangrenous or perforated appendicitis or a neoplasm (mucinous neoplasm, carcinoid), arrange surgical oncology follow-up with appropriate staging and colonoscopy.
• Complicated appendicitis with a contained abscess or phlegmon: nonoperative management with IV antibiotics plus percutaneous drainage of an accessible collection succeeds in more than 80%; continue antibiotics about 4–7 days after adequate source control, then switch to oral.
• Interval appendectomy after successful nonoperative treatment of an abscess or phlegmon is selective — offer it for recurrent symptoms or a persistent appendicolith, and strongly consider it in patients over 40 given a 3–17% underlying neoplasm risk. Colonoscopy and cross-sectional imaging are recommended in nonoperative patients over 40 before deferring surgery.
• VTE prophylaxis per risk assessment, glucose control, and smoking and opioid counseling as applicable.

Monitoring and disposition

• A medical-surgical floor is appropriate for a stable patient. Serial abdominal exams every 8–12 hours, vitals every 4 hours, and trend WBC and CRP if managed nonoperatively.
• Expect defervescence and pain improvement within 24–48 hours with either strategy; failure to improve is the key trigger to reassess.
• Discharge criteria: afebrile, tolerating oral intake, pain controlled on oral analgesia, ambulating, and passing flatus.
• Surgical follow-up in 2–4 weeks for wound check and pathology review; nonoperative patients need counseling on recurrence symptoms and, if over 40, colonoscopy or imaging.

Escalate care if

• Generalized peritonitis, hemodynamic instability, or organ dysfunction — emergent appendectomy with broadened coverage (piperacillin-tazobactam 4.5 g IV every 6 hours) and ICU-level care.
• On nonoperative management there is no clinical improvement within 24–48 hours, or worsening pain, rising WBC or CRP, or persistent fever — repeat imaging and proceed to appendectomy.
• Repeat CT shows a new abscess ≥ 3 cm — interventional radiology percutaneous drainage plus continued IV antibiotics; surgery if drainage fails or sepsis persists.
• Post-appendectomy fever, ileus, or leukocytosis beyond postoperative day 3–4 — CT abdomen and pelvis for organ-space infection or stump leak, resume broad-spectrum antibiotics, and involve surgery.
• Healthcare-associated exposure, recent antibiotics, or immunosuppression — broaden empirically to piperacillin-tazobactam and tailor to cultures.

Duration

Uncomplicated appendicitis treated with appendectomy needs only the perioperative dose. Antibiotics-first management runs about 7 days (3 IV, 4 oral). Complicated appendicitis with an abscess is treated for approximately 4–7 days after adequate source control.

Advertencias

• This overview assumes an immunocompetent, non-pregnant adult without a prior appendiceal abscess; immunosuppression, pregnancy, or prior complicated episodes shift management toward operative treatment.
• Appendicolith, gangrenous change, abscess, or diffuse peritonitis are contraindications to nonoperative management.
• Whether antibiotics add benefit over observation alone in CT-confirmed uncomplicated appendicitis is unsettled; standard practice remains to give antibiotics when pursuing nonoperative management.
• Avoid fluoroquinolones with QT-prolonging drugs, known tendinopathy, or prior intolerance; metronidazole interacts with alcohol and warfarin.
• Age over 40 raises concern for an occult appendiceal or cecal neoplasm — do not manage nonoperatively without a plan for colonoscopy or imaging.

Referencias

1. Antibiotics Versus Surgery for Uncomplicated Acute Appendicitis in Adults: A Meta-analysis of Long-term Outcomes and Risk Factors for Failure. (2026) · Revisión sistemática“The 1-year treatment success rate was significantly lower in the antibiotics group (73.8%) versus surgery (98.1%)”
2. Effect of antibiotic therapy versus no antibiotics on nonoperative management outcomes in uncomplicated appendicitis: A systematic review and meta-analysis. (2026) · Revisión sistemática“Current evidence remains insufficient to determine whether antibiotics provide additional benefit over observation in the conservative management of uncomplicated appendicitis.”
3. Non-operative Management of Uncomplicated Appendicitis: A Review of Indications, Safety, and Clinical Algorithms. (2026) · Revisión narrativa“Uncomplicated or simple appendicitis can be defined as an inflammatory condition of the appendix in which the organ appears inflamed and phlegmonous but lacks evidence of necrosis or perforation.”
4. Clinical outcomes and optimal indications for nonoperative management of acute appendicitis in adult patients: a comprehensive literature review. (2025) · Revisión narrativa“Nonoperative management with antibiotics does not significantly increase the perforation rate, indicating that the decision to delay appendectomy does not increase the risk of postoperative complications.”