Obstruction-driven inflammation of the appendix; classic periumbilical-to-RLQ pain with peritoneal signs.
Also known as: appendicitis, acute appendicitis
Overview
Acute inflammation of the vermiform appendix, typically due to luminal obstruction (fecalith, lymphoid hyperplasia, tumor) with secondary bacterial overgrowth, distension, ischemia, and risk of perforation.
Epidemiology
Lifetime risk ~7-8%. Most common surgical abdominal emergency. Peak incidence age 10-30; can occur at any age. Slight male predominance.
🔒 Free preview limit reached
Keep reading — start your free trial
You've read your 2 free diagnosis previews. Create your free account to unlock the full Acute Appendicitis outline — plus all 514 diagnoses, 3,500+ board-style questions, flashcards, and an AI tutor. Your 7-day free trial includes everything, and there's no credit card required.
Clinical diagnosis supported by imaging. Histopathology confirms post-operatively.
Labs
CBC — mild to moderate leukocytosis (10-18,000) with left shift; very high WBC suggests perforation
BMP, CRP
Urinalysis — exclude UTI; mild pyuria/hematuria possible from inflamed appendix adjacent to ureter
Pregnancy test in women of childbearing age (CRITICAL before imaging or surgery)
Lactate if septic
Imaging
CT abdomen/pelvis with contrast — modality of choice in adults; sensitivity and specificity >95%; findings: dilated appendix >6 mm, wall thickening, periappendiceal fat stranding, fluid, abscess, fecalith
Ultrasound — first-line in children and pregnant women to avoid radiation; operator-dependent
MRI — alternative in pregnancy if ultrasound non-diagnostic
Alvarado score (MANTRELS) ≥7 supports appendicitis; useful for risk stratification but does not replace imaging
Diagnostic algorithm
flowchart TD
A[Suspected appendicitis<br/>RLQ pain + anorexia + fever] --> B[Labs: CBC, CRP<br/>BHCG in women]
B --> C{Pregnant?}
C -->|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[IV antibiotics +<br/>laparoscopic appendectomy]
F -->|Complicated:<br/>perforation/abscess| H{Abscess<br/>drainable?}
H -->|Yes| I[Percutaneous drain<br/>+ IV antibiotics<br/>+ interval appendectomy]
H -->|No - peritonitis| J[Emergent surgery]
F -->|Equivocal| K[Observation +<br/>serial exams<br/>± repeat imaging]
Acute appendicitis diagnostic and treatment pathway.
Treatment
First-line
NPO, IV fluids, analgesia, antiemetics
IV antibiotics covering Gram-negative and anaerobic flora — piperacillin-tazobactam, ceftriaxone + metronidazole, or ertapenem; administer pre-operatively
Laparoscopic appendectomy — standard of care; lower wound infection rate and faster recovery vs open
Open appendectomy — alternative when laparoscopy contraindicated
Second-line / adjunct
Nonoperative management with antibiotics alone — emerging option for uncomplicated appendicitis without fecalith (CODA trial); failure/recurrence ~40% at 5 yr; appropriate for selected patients who decline or cannot undergo surgery
Percutaneous drainage of abscess + interval appendectomy 6-12 weeks later — for contained perforation with abscess (Hinchey-like approach)
Open laparotomy if diffuse peritonitis, perforation with diffuse contamination, or hemodynamic instability
Appendiceal tumor management depends on histology (carcinoid, mucinous, adenocarcinoma) — may require right hemicolectomy
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
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 about ~40% recurrence at 5 yr.
Appendectomy WITHOUT a clinical or imaging diagnosis is no longer standard — image first when possible.
Pylephlebitis: persistent fever and bacteremia after appendicitis — CT shows portal vein thrombosis; treat with prolonged antibiotics ± anticoagulation.
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 2017 — Rao A et al. Eastern Association for the Surgery of Trauma Guidelines on the Management of Acute Appendicitis. J Trauma Acute Care Surg 2017
Practice Gastrointestinal questions on FirstPassPA
Turn this outline into retention. 3,500+ board-style questions with an AI tutor that explains every answer — free to start, no card required.
Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants.