- Clinical science
Acute appendicitis refers to acute inflammation of the appendix, typically due to an obstruction of the appendiceal lumen. In both children and adults, it is the most common cause of acute abdomen requiring emergency surgical intervention. The characteristic features of acute appendicitis are periumbilical abdominal pain that migrates to the right lower quadrant (RLQ), anorexia, nausea, fever, and RLQ tenderness. In association with neutrophilic leukocytosis, these features are sufficient to make a clinical diagnosis of acute appendicitis. Imaging (e.g., abdominal CT with IV contrast, abdominal ultrasonography) may be considered if the clinical features are inconclusive. The current standard of management of acute appendicitis is emergency appendectomy (open or laparoscopic) and broad-spectrum antibiotics. Conservative management, which includes bowel rest, antibiotics, and analgesics, is indicated in patients with an inflammatory appendiceal mass (phlegmon) or an appendiceal abscess because surgical intervention is associated with a higher risk of complications in these patient groups. Interval appendectomy 6–12 weeks after resolution of the acute episode can be performed in these patients to prevent a recurrence.
Caused by obstruction of the appendiceal lumen due to: 
- Lymphoid tissue hyperplasia; (60% of cases): most common cause in children and young adults
- ; and fecal stasis (35% of cases): most common cause in adult
- Neoplasm; (uncommon): more likely in patients > 50 years of age 
- Parasitic infestation (uncommon): e.g., Enterobius vermicularis, Ascaris lumbricoides, and species of the Taenia and Schistosoma genera 
Obstructed proximal appendiceal lumen (closed-loop obstruction), resulting in: 
- Stasis of mucosal secretions → bacterial multiplication and local inflammation → transmural spread of infection → clinical features of appendicitis
- Increased intraluminal pressure → obstruction of veins → edema of the appendiceal walls → obstruction of capillaries → ischemia → gangrenous appendicitis with/without perforation
- Inflammation can spread to serosa, leading to peritonitis
Migrating abdominal pain: most common and specific symptom
- Typically constant and rapidly worsens
- Most patients present within 48 hours of symptom onset.
- Initial diffuse periumbilical pain; : caused by the irritation of the visceral peritoneum (pain is referred to T8–T10 dermatomes) 
- Localizes to the RLQ within ∼ 12–24 hours; : caused by the irritation of the parietal peritoneum
- Associated nonspecific symptoms
Clinical signs of appendicitis 
- McBurney point tenderness (RLQ tenderness)
- RLQ guarding and/or rigidity
- (Blumberg sign), especially in the RLQ
- Rovsing sign: RLQ pain elicited on deep palpation of the LLQ 
- Psoas sign
- Obturator sign: RLQ pain on passive internal rotation of the right hip with the hip and knee flexed
- Hyperesthesia within Sherren triangle: formed by the anterior superior iliac spine, umbilicus, and symphysis pubis
- Lanz point tenderness: at the junction of the right third and left two-thirds of a line connecting both the anterior superior iliac spines
- Pain in the Pouch of Douglas: pain elicited by palpating the rectouterine pouch on rectal examination
- Baldwin sign: pain in the flank when flexing the right hip (suggests an inflamed retrocecal appendix)
- Acute appendicitis is often a clinical diagnosis.
- Laboratory tests
- Abdominal ultrasound ;: non-compressible and enlarged appendix (> 6–8 mm)
- Abdominal CT scan (∼ 98% sensitivity): periappendiceal streaking and enlarged appendix
Abnormal urine analysis does not necessarily rule out appendicitis!
Appendicitis is a clinical diagnosis. Further examination, such as blood tests and imaging, is not essential to diagnosis but may be considered if the diagnosis is uncertain!References:
- The appendix is composed of the same four histological layers of the alimentary canal.
- See “Microscopic anatomy” in appendix. for the histological features of a healthy
- Transmural neutrophilic infiltration is the characteristic histological feature of acute appendicitis.
- Blood vessel thrombosis, mucosal ulceration, and/or gangrene of the appendiceal wall may also be present.
- See .
- (especially in elderly individuals)
- and renal colic
- psoas sign) (in patients with a positive
- Gynecological diseases (e.g. pelvic inflammatory disease, )
The differential diagnoses listed here are not exhaustive.
- Conservative therapy is considered in exceptional cases or if findings are unclear ("soft" signs).
- Bowel rest (keep patient NPO), IV fluid therapy, and observation
- Antibiotics; with anaerobic and gram negative cover (e.g., cefazolin and metronidazole)
Suspected appendicitis warrants surgical intervention!
- Surgical approach may be laparoscopic or open and is decided on a case-by-case basis
- Urgent general surgery consult for consideration of appendectomy (versus a conservative approach)
- IV fluid therapy
- Parenteral analgesics (opioid analgesics preferred) 
- Parenteral antiemetics (see antiemetics)
- Empiric IV antibiotics
- Treat any complications
- Consider nasogastric tube insertion.
- Transfer to OR or admit to surgical service.
- Serial abdominal exam
Inflammatory appendiceal mass (appendiceal phlegmon)
- Description: an ill-defined mass of inflammatory periappendiceal tissue
- Clinical features: manifests as a tender mass in the RLQ in a patient who is not acutely ill
- Management: conservative (bowel rest, IV fluids, IV antibiotics, with/without interval appendectomy)
- Description: irreversible necrosis of the appendiceal wall
- Clinical features
- Management: immediate appendectomy and IV antibiotics
- Description: rupture of the appendix
- Clinical features: : manifests similarly to gangrenous appendicitis, with signs of localized/generalized peritonitis and ↓ bowel sounds
- Management: immediate appendectomy and IV antibiotics
- Description: localized collection of pus and necrotic tissue that forms around an inflamed appendix, which typically follows an untreated perforated appendix
- Clinical features: manifests as a tender mass in the RLQ in an acutely ill patient (i.e., high-grade fever, with/without paralytic ileus, leukocytosis, signs of sepsis)
- Management: IV antibiotics, CT-guided drainage of the abscess if > 4 cm, and interval appendectomy 
- Description: septic thrombosis of the portal vein or its branches
- Etiology: : complication of intraabdominal sepsis (e.g., due to perforated appendicitis, diverticulitis, or necrotizing pancreatitis)
- Clinical features: fever, abdominal pain
- Management: broad-spectrum antibiotics
- Prognosis: Thrombosis of the portal circulation can result in bowel infarction and death.
We list the most important complications. The selection is not exhaustive.
- Uncomplicated appendicitis with adequate management (surgical intervention) has an excellent prognosis. 
- Perforation and peritonitis: ∼ 1% mortality rate 
- Up to 20% of patients are found to have a normal appendix following surgery. 
- The mortality rate is higher (∼ 5%) in elderly patients with complicated appendicitis. 
Appendicitis in children 
- The reliability of signs and symptoms in children is lower.
- Ultrasound is the diagnostic procedure of choice.
Appendicitis in pregnancy 
- Atypical (higher) pain localization
- Perforated appendix is associated with a higher risk of fetal loss
- Ultrasound is the diagnostic procedure of choice
Appendicitis in older patients 
- Clinical presentation
- Consider they usually have multiple comorbidities.
- CT scan or MRI imaging is preferred because of atypical presentation and higher malignancy rates
Children, pregnant women, and the elderly are at a higher risk of perforation!