Acute inflammation of the vermiform appendix secondary to appendiceal lumen obstruction, almost always requiring inpatient operative management

  • The appendix is a true diverticulum of the cecum
  • Appendiceal obstruction caused by fecaliths (hard faecal mass), calculi, infectious processes or tumours leads to increased luminal and intramural pressure
  • Occlusion of small vessels occurs with subsequent engorgement, ischaemia and necrosis of the appendiceal wall
  • Bacterial overgrowth occurs within the diseased appendix
  • Most cases are aged 10-30, with a predominance in males and a lifetime risk ~7%

Clinical features


  • RLQ pain
  • Anorexia
  • Nausea and vomiting (usually follow onset of pain)
  • Migratory pain (50%)
  • Fever (late sign)
  • Diarrhoea (uncommon)
  • The absence of PV discharge and/or bleeding is important to clarify in differentiating from other causes of abdominal pain including ectopic pregnancy and pelvic inflammatory disease


  • Fever
  • Tenderness over McBurney’s point
  • Rovsing sign
  • Psoas sign (retrocecal appendix)
  • Obturator sign (pelvic appendix)
  • Always perform a testicular examination



  • WCC
  • CRP
  • LFT
  • Lipase
  • B-HCG
  • Neutrophil to lymphocyte ratio (NLR) > 5 has 90% sensitivity and specificity for appendicitis, NLR > 9 has 100% specificity for complicated appendicitis


Modified Alvarado score

The Alvarado score is an excellent clinical guide to assist in the diagnosis of appendicitis. It assigns points to the salient features in the history, examination and laboratory values suggestive of acute appendicitis.

The key features in the history are:

  • Migration of pain to the right lower quadrant from the central abdomen (1 point) 
  • Anorexia (1 point) 
  • Nausea or vomiting (1 point) 

On examination:

  • Right lower quadrant tenderness (1 point) 
  • Elevate temperature > 37.3 degrees (1 point) 
  • *Rebound tenderness (1 point) — assessing for rebound tenderness causes the patient unnecessary discomfort, instead assess for localised peritonism by examining for tenderness on light percussion over McBurney’s point. 

Laboratory values 

  • Leukocytosis >10,000 (2 points) 
  • Leukocyte left shift (1 point) 

Scores of 7 or above support appendicitis as the likely diagnosis. 


Performing imaging reduces the negative appendectomy rate (NAR) 4-fold

  • CT is modality of choice – 95% sensitivity, 96% specificity
  • USS is preferred in pregnant females and children, but is both operator and patient dependent. A normal appendix is not visualised in at least 50% of cases, leading to indeterminate examination
  • There is no role of plain AXR in the assessment of suspected appendicitis
  • 20% of healthy patients without appendicitis will have an appendiceal diameter > 7mm, therefore diagnosing appendicitis based on this alone is not advised
CT imaging features of appendicitis
  • Enlarged appendiceal double-wall thickness (> 6mm)
  • Appendiceal wall thickening (> 2mm)
  • Peri-appendiceal fat stranding
  • Appendiceal wall enhancement
  • Appendicolith (seen in minority)

Differential diagnosis
  • Differential diagnosis depends on the patient’s age and sex
  • In young males with RIF pain there are few differential diagnoses, serious differentials to consider are a Meckel’s diverticulum and testicular torsion
  • In reproductive age females, gynaecological differentials should be considered including ovarian cyst rupture, PID, pregnancy, ectopic pregnancy and ovarian torsion
  • In older adults, diverticulitis is an important differential diagnosis — a redundant sigmoid colon may lie in the right iliac fossa with sigmoid diverticulitis mimicking appendicitis. Asian people tend to develop diverticula of the right colon and right side diverticulitis.
  • It is important to consider hernias as a cause of RIF pain. Careful examination of a patient while supine and standing may reveal a femoral hernia or Spigelian hernia that would be missed on cursory examination
  • In thin elderly women, consider obturator hernias — these are difficult to diagnose clinically
  • Pain radiating around from the back to the RIF may be revealed to be from shingles on close inspection of the skin for vesicles
  • Loin to groin pain is suggestive of urolithiasis
  • In Valentino Syndrome, fluid expelled from a perforated peptic ulcer collects in the right paracolic gutter mimicking appendicitis (pancreatitis may mimic appendicitis in the same fashion)
  • Terminal ileitis from infectious or inflammatory aetiology will also mimic appendicitis
  • Ileocaecal intussusception, retrocaecal internal hernias and neutropenic colitis (typhlitis) are rare but important differentials
  • Mimics that usually require supportive care only include mesenteric adenitis, epiploic appendagitis and omental infarction


Management approach is divided into uncomplicated (perforated) and complicated (perforated) appendicitis.


  • Refers to acute appendicitis without clinical or radiographic signs of perforation (e.g. inflammatory mass, phlegmon, abscess)
  • Laparoscopic or open appendectomy remains the treatment of choice
  • Patients can wait 12-24 hours before surgery without increase in rates of perforation or other complications. However, these patients, including those who present to ED overnight and who face delay for appendectomy, should receive empirical antibiotic therapy for perforated appendicitis (ceftriaxone and metronidazole)

Numerous studies have evaluated conservative management in cases of uncomplicated appendicitis. In uncomplicated appendicitis where the appendiceal orifice is not obstructed by a faecolith, the index presentation can be managed with intravenous antibiotics only in the majority of cases. However, there is a consistent representation rate of 35% with recurrent appendicitis within 12 months. Furthermore, quality of life has been demonstrated to the lower on followup in the conservatively managed cohort in randomised controlled studies (COMMA Trial). As such, appendicectomy on index presentation is best practice.  


  • Refers to acute appendicitis with a contained perforation (phlegmon or abscess) or free perforation
  • 15-20% of presentations
  • Risk factors include male sex and older age
  • Time course does not reliably distinguish — 20% present within 24 hours of pain onset

Acute appendicitis with a free perforation should go to theatre as soon as possible (within 6 hours max) as this will develop into a fulminant peritonitis. 

In cases of an appendiceal phlegmon it is reasonable to treat operatively or settle the inflammation with a course of intravenous antibiotics then book the patient for an interval appendicetomy in 6 weeks time. 

In cases of an appendiceal abscess it may be prefered to drain the abscess percutaneously, settle the inflammation with intravenous antibiotics then book the patient for an interval appendicetomy in 6 weeks time. 

Older adults with acute appendicitis should be followed up with an outpatient colonoscopy.

Handy tips
  • Always perform a testicular examination in male patients presenting with suspected appendicitis
  • Important differentials in the female population include ectopic pregnancy, pelvic inflammatory disease, and tubo-ovarian abscess — a detailed history enquiring about PV discharge/bleeding can assist diagnostic evaluation

Further reading

MBBS MSurg General Surgery Registrar from Perth, Western Australia

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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