Acute Appendicitis

Risk factors

• Age (peak 10-30)
• Male sex (slight)
• Family history
• Low-fiber diet (controversial)
• Lymphoid hyperplasia (viral illness in children)
• Fecaliths, foreign bodies, tumors (carcinoid is the most common appendiceal tumor)

Pathophysiology

Luminal obstruction → mucus accumulation → bacterial overgrowth (E. coli, Bacteroides) → distension → mucosal ischemia → mural inflammation and necrosis → perforation within 24-72 h. Perforation leads to localized abscess (walled-off) or diffuse peritonitis.

Clinical presentation

Differential diagnosis

• Mesenteric adenitis — Children, recent viral URI, low-grade fever, less severe pain; observation, no surgery
• Crohn disease (ileitis) — Chronic symptoms, weight loss, diarrhea; MRE diagnostic
• Cecal diverticulitis (Asian patients) — Mimics appendicitis; CT diagnostic
• Right-sided diverticulitis — Less common than left; CT distinguishes
• Ovarian torsion / ectopic pregnancy / PID / hemorrhagic cyst — Women — pregnancy test, pelvic US; pelvic exam mandatory
• Renal colic / pyelonephritis — Flank pain, hematuria, CVA tenderness, dysuria
• Epiploic appendagitis — Localized abdominal pain; characteristic CT finding (fat-density lesion); self-limited
• Meckel diverticulum — Children with painless lower GI bleed or obstruction; Meckel scan
• Cholecystitis (in patient with rotational anomaly or atypical anatomy) — RUQ pain, fever; ultrasound
• Testicular torsion — Acute scrotal pain, absent cremasteric reflex; ultrasound

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A["Suspected appendicitis<br/>RLQ pain + anorexia + fever"] --> B["Labs: CBC, CRP<br/>hCG in women"]
  B --> C{"Pregnant?"}
  C -->|No| S{"Classic presentation,<br/>high-risk score, age under 40?"}
  S -->|Yes| G
  S -->|No| D["CT abd/pelvis<br/>with contrast"]
  C -->|Yes| E["Ultrasound first<br/>MRI if equivocal"]
  D --> F{"Appendicitis<br/>confirmed?"}
  E --> F
  F -->|Uncomplicated| G["Early surgical consult<br/>IV antibiotics +<br/>laparoscopic appendectomy"]
  F -->|"Complicated:<br/>perforation/abscess"| H{"Abscess<br/>drainable?"}
  H -->|Yes| I["Percutaneous drain + IV antibiotics<br/>interval appendectomy only if recurrent<br/>age 40 or older: colonoscopy + interval CT"]
  H -->|"No - peritonitis"| J["Emergent surgery<br/>laparoscopic preferred"]
  F -->|Equivocal| K["Observation +<br/>serial exams<br/>± repeat imaging"]

Treatment

Complications

• Perforation (especially in delayed diagnosis — elderly, pregnant, immunocompromised)
• Periappendiceal abscess
• Diffuse peritonitis, sepsis
• Wound infection, intra-abdominal abscess after surgery
• Stump appendicitis (rare)
• Adhesive small bowel obstruction (years later)
• Pylephlebitis (septic portal vein thrombosis) — rare but life-threatening
• Appendiceal stump leak / postoperative intra-abdominal infection — early high fever, tachycardia and peritoneal signs after appendectomy; CT and prompt source control

PANCE pearls

• Anorexia is highly sensitive — appendicitis is unlikely if the patient is hungry.
• Vomiting BEFORE pain suggests gastroenteritis; vomiting AFTER pain suggests appendicitis.
• Always obtain pregnancy test in women of childbearing age BEFORE imaging.
• Ultrasound is first-line in children and pregnant women to avoid radiation.
• Pregnancy shifts appendix cephalad and laterally — third-trimester appendicitis can present with RUQ or right flank pain.
• Atypical presentations (elderly, immunocompromised) lead to higher perforation rates — maintain low threshold for imaging.
• Carcinoid is the most common appendiceal tumor; usually incidental at appendectomy; tumors >2 cm or with mesenteric invasion require right hemicolectomy.
• Nonoperative management with antibiotics (CODA trial, NEJM 2020) is a reasonable alternative for uncomplicated appendicitis without fecalith — counsel that ~3 in 10 need appendectomy within 90 days (4 in 10 with an appendicolith) and ~40% by 5 yr (APPAC).
• Get early surgical consultation. A young patient (<40) with a classic high-probability presentation (e.g., Alvarado 9-10) may proceed to laparoscopy without CT, and imaging must never delay surgery; image when risk is intermediate or the presentation atypical, in older adults, and in women of reproductive age (US first if pregnant).
• Pylephlebitis: persistent fever and bacteremia after appendicitis — CT shows portal vein thrombosis; treat with prolonged antibiotics ± anticoagulation.
• Pregnancy: once ultrasound (or MRI) confirms appendicitis, appendectomy (laparoscopic preferred) is recommended in any trimester; antibiotics alone are not recommended, because perforation sharply increases fetal loss.

References

• WSES 2020 — Di Saverio S et al. Diagnosis and treatment of acute appendicitis: 2020 update of the WSES Jerusalem guidelines. World J Emerg Surg 2020;15:27
• CODA Trial — Flum DR et al. A Randomized Trial Comparing Antibiotics with Appendectomy for Appendicitis. NEJM 2020;383:1907-1919
• EAST 2019 — Rushing A, Bugaev N, Jones C, et al. Management of acute appendicitis in adults: A practice management guideline from the Eastern Association for the Surgery of Trauma. J Trauma Acute Care Surg 2019;87(1):214-224
• APPAC 5-year — Salminen P, Tuominen R, Paajanen H, et al. Five-Year Follow-up of Antibiotic Therapy for Uncomplicated Acute Appendicitis in the APPAC Randomized Clinical Trial. JAMA 2018;320(12):1259-1265
• SAGES 2024 — Kumar SS, Collings AT, Wunker C, et al. SAGES guidelines for the use of laparoscopy during pregnancy. Surg Endosc 2024;38(6):2947-2963