Acute appendicitis


The natural history of appendicitis has been described in three stages: (1) a normal appendix, (2) uncomplicated acute appendicitis, and (3) complicated appendicitis, according to their macroscopic and microscopic appearance and clinical relevance. The high morbidity and occasional mortality associated with acute appendicitis are related to delay in presentation by patients or delay in diagnosis by the clinician. These delays may result in complications like gangrene, perforation, appendiceal mass, and peritonitis, all of which would prolong hospital stay and increase the cost of treatment.


Clinical signs and symptoms

  • Pain across the abdominal area with location in the lower right quadrant of the abdomen
  • Nausea and/or vomiting soon after abdominal pain begins
  • Elevated temperature
  • Abdominal tenderness (sign of complicated acute appendicitis)

Laboratory markers

  • White blood cell
  • Leucocyte shift to left (>75 %)
  • C-reactive protein


Unfortunately, the clinical presentation of appendicitis is often inconsistent. While the clinical diagnosis may be clear in patients presenting with classic signs and symptoms, atypical presentations may result in delay in treatment. Therefore, diagnostic scoring systems have been described with the aim to provide clinical probabilities that a patient has acute appendicitis. The development of these scores may contribute to diagnosis and by easily applicable clinical criteria and simple laboratory tests a score which classifies the probability of diagnosis may be attributed to the patient.

Alvarado Score

Diagnostic criteria Value
Migration pain to RLQ 1
Anorexia 1
Nausea–vomiting 1
Tenderness in RLQ 2
Cough/percussion tenderness 2
Elevated temperature ≥ 37.3 °C 1
Leucocytosis (>10 x 103/L) 2
Leucocyte shift to left (>75 %) 1
Total score 10
  • A score 0-4 indicates low probability of acute appendicitis
  • A score >5 indicates a probable appendicitis
  • A score >8 indicates a very probable appendicitis

Andersson appendicitis inflammatory response (AIR)

Diagnostic criteria Value
Pain or tenderness in right 1
Lower quadrant 1
Vomiting 1
Rebound tenderness or muscular defence
Sight 1
Moderate 2
Strong 3
WBC Count(>75 %)
10-14.9×109/1 1
≥15.0×109/1 2
Proportion neutrophils
70%-84% 1
≥85% 2
CRP concentration
10-49mg/1 1
≥50mg/1 2
Body temperature ≥38.5C 1
  • A score of 0-4 indicates low probability of acute appendicitis
  • A score 5-8 indicates active observation with rescoring/ imaging or diagnostic laparoscopy according to the local tradition
  • A score of 9-12 indicates high probability


  • US
  • CT

Imaging findings

  • Diameter of the appendix > 6 mm
  • Single wall thickness ≥ 3 mm
  • Increased echogenicity of local mesenteric fat
  • Appendicolith: hyperechoic with posterior shadowing
  • Free fluid surrounding appendix
  • Local abscess formation
  • Enlarged local mesenteric lymph nodes
  • Thickening of the peritoneum
CT is the most accurate imaging study for evaluating suspected acute appendicitis and alternative etiologies of right lower quadrant pain. In children, ultrasound is the preferred initial examination, because it is nearly as accurate as CT for the diagnosis of acute appendicitis without use of ionizing radiation.
In pregnant women, ultrasound is preferred initially, with MRI as a second imaging examination in inconclusive cases.
The decision to obtain US or CT scan studies depends on institutional preference and the available user expertise, although patient age, sex, and body habitus are important influencing factors.
Proposals of staged algorithmics with a step-up approach with CT performed after an inconclusive or negative US were proposed.


Uncomplicated appendicitis

  • Open/laparoscopic appendectomy. Post-operative antibiotics are unnecessary if source control is adequate.
  • Antibiotic therapy alone (in selected patients).

Although the standard treatment for acute appendicitis has historically been the appendectomy, the medical community has recently seen a notable increase in the use of antibiotic therapy as a primary means of treatment. Antibiotic therapy is a safe means of primary treatment for patients with uncomplicated acute appendicitis, but it is less effective in the long-term due to significant recurrence rates and needs the certainty of a CT proven diagnosis of uncomplicated appendicitis.

Complicated appendicitis

Open/laparoscopic appendectomy with antibiotic therapy for no more of 4 days if source control is adequate.

Patients who have ongoing signs of infection or systemic illness (ongoing infection) beyond 5 to 7 days of antibiotic treatment, should warrant a diagnostic investigation.

Empiric antibiotic regimens. Normal renal function

The major pathogens involved in community-acquired acute appendicitis are Enterobacteriaceae, Streptococcus species, and anaerobes (especially B. fragilis).

One of the following antibiotics
Amoxicillin/clavulanate 1.2-2.2 g 8-hourly
Piperacillin/Tazobactam 4.5 g 6-hourly (in critically ill patients)
Ceftriaxone 2 g 24-hourly + Metronidazole 500 mg 6-hourly
Cefotaxime 2g 8-hourly + Metronidazole 500 mg 6-hourly
In patients with beta-lactam allergy
A fluoroquinolone-based regimen
Ciprofloxacin 400 mg 8/12-hourly + Metronidazole 500 mg 6- hourly
In patients at high risk for infection with community-acquired ESBL-producing Enterobacteriaceae
Ertapenem 1 g 24-hourly
In patients at high risk for infection with Enterococci including immunocompromised patients or patients with recent antibiotic exposure consider use of Ampicillin 2 g 6-hourly if the patients are being treated by Ertapenem.