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B5. Acute appendicitis

Acute appendicitis refers to acute inflammation of the vermiform appendix and is a common cause of acute abdomen. Rapid management is important to prevent complications such as perforation of the appendix.

The lifetime incidence of appendicitis is 9% for men and 7% for women. The peak incidence is in the second and third decades of life, but it may occur at any age. The incidence of acute appendicitis has been decreasing since the 1970s, for reasons not known.

Etiology

The etiology of acute appendicitis is largely unknown; it frequently occurs in healthy, young people. Outside age, gender, and family history, no real risk factors are known.

Pathology

In most cases, an obstruction of the appendix lumen is identified, but not always. Obstruction may be caused by hard faecal masses, calculi, lymphoid tissue hyperplasia, or tumours. An obstruction may lead to increase in luminal and intramural pressure, which may cause thrombosis in small vessels, causing localised oedema. The obstruction of the venous outflow leads to ischemic injury and stasis of luminal contents. This gives bacteria a perfect place to proliferate in, which in turn will trigger the inflammatory responses. Tissue edema and neutrophilic infiltration of the lumen, muscular wall and periappendiceal tissue will take place. The pathological criterium to diagnose acute appendicitis is neutrophilic infiltration of the muscularis propria. In more severe cases, focal abscesses may form within the wall, and this is then called an acute suppurative appendicitis. These may also progress to large areas of hemorrhagic ulceration and gangrenous necrosis, into an acute gangrenous appendicitis, which is often followed by rupture and resulting peritonitis.

Inflammatory stages

  • Catarrhal (acutely inflamed) appendicitis
    • Non-destructive microscopic evidence of inflammation, appendix is erythematous and swollen
  • Suppurative appendicitis
    • Bacterial inflammation, ulceration occurs
  • Phlegmonous appendicitis
    • Destructive, appendix is filled with purulent fluid
  • Gangrenous appendicitis
    • Necrotic appendix, with black necrotic areas
  • Perforated/ruptured appendicitis
    • Perforation -> localised periappendicular abscess or faecal peritonitis

“Complicated” appendicitis refers to the presence of periappendicular infiltration, periappendicular abscess, perforation, or peritonitis.

Clinical features

The classical clinical features of acute appendicitis are:

  • Initial diffuse periumbilical pain which translocates into peritonitic pain in the right lower quadrant
  • Anorexia (decreased appetite)
  • Nausea and vomiting

Other possible symptoms include fever and abnormal bowel habits.

Various physical signs may be positive in acute appendicitis, including McBurney point tenderness, Rovsing sign, psoas sign, and obturator sign. Because of the localised peritonitis over the appendix, peritonitis signs like guarding, rebound tenderness, and heel-drop test may be positive and elicit pain in the right lower quadrant.

Diffuse peritonitic signs may be a sign of perforated appendicitis. The longer the duration of the symptoms, the higher the risk that the appendix has ruptured. After 48h, 65% of appendixes haved perforated. Following perforation, the symptoms usually alleviate temporarily, as the pressure is relieved, until the condition worsens again.

There is considerable anatomical variation in the location of the free end of the appendix, which will influence the site of pain and findings on physical examination. A retrocaecal appendix may not cause localised tenderness in the right lower quadrant (because localised peritonitis does not occur). A pelvic appendix may cause localised tenderness well below McBurney’s point.

Physical signs of acute appendicits

Rovsing sign refers to pain in the right iliac fossa upon deep palpation of the left iliac fossa.

Psoas sign is elicited by asking the patient to lie on the left side with the hip flexed, and the examiner passively extending the right hip. This causes pain in the right lower quadrant in the case of appendicitis because the right psoas muscle lies beneath the appendix, and so stretching or contracting it elicits pain.

Obturator sign is elicited by the examiner flexing the patient’s right hip and knee, followed by internal rotation of the right hip. This causes pain in the right lower quadrant in the case of appendicitis because the right obturator internus muscle lies beneath the appendix, and so stretching or contracting it elicits pain.

Diagnosis and evaluation

A normal WBC count is unlikely in the case of acute appendicitis, as leukocytosis is present in > 80% of cases. The higher the WBC count, the higher the chance for gangrenous or perforated appendicitis. CRP is also frequently elevated.

In some countries (like Norway), imaging is usually not performed if the clinical presentation is very suspicious for acute appendicitis. If imaging is to be performed, low-dose abdominal CT with contrast or abdominal ultrasound are the modalities of choice. These may reveal suspicious features such as thickening and enhancement of the appendiceal wall, and rule out other pathologies as well. Imaging will also reveal features of perforation if present, like faeces or air in the abdominal cavity. Ultrasound cannot visualise a retrocoecal appendix, and is therefore not completely sensitive for acute appendicitis. The presence of bowel gas also reduces visibility.

Only histology can confirm the diagnosis of appendicitis, although one can usually tell whether the appendix is inflamed or not during surgery.

Treatment

Immediate laparoscopic appendectomy is the gold standard for management of acute appendicitis. In case of perforated appendicitis, the patient may proceed directly to surgery as usual, or surgery may be postponed temporarily while the patient receives antibiotics and percutaneous drainage.

Laparoscopic appendectomy is a relatively simple surgical procedure and is most surgeons’ first surgical procedure. It’s sometimes said that that the function of the appendix in the modern times is to allow young surgeons to improve their surgical technique.

If one, suspecting acute appendicits, opens the patient's abdominal cavity and discovers that the appendix is not inflamed, some advocate for removing the (healthy) appendix anyway, seeing as you're already there and it will prevent appendicitis in the future, but others advocate for leaving it as there is no longer any indication for surgery. Removing the healthy appendix avoids the problem of assuming that the appendix is absent should the patient appear to present with appendicitis subsequently, althought this problem is easily avoided by the use of patient health records or patient history.

Studies have shown that antibiotic therapy can be as effective as surgery for managing the initial presentation of appendicitis. However, these studies also conclude that this carries with it moderate risk of recurrence and missed neoplasms. As such, surgery remains the first choice.