Acute Appendicitis

Definition Acute inflammation of the vermiform appendix.

Incidence Very common. 1 in 400 people per year. 7-8% of people develop appendicitis in their lifetime.

Age Frequent in young children and the elderly but peak incidence in second and third decades of life.

Sex Slightly more common in males compared to females. Lifetime risk of 8.6% in males and 6.7% in females.

Geography No definite geographical variations.

Aetiology In most cases it is thought that appendicitis is caused by obstruction of the lumen. This may be secondary to lymphoid hyperplasia, a faecolith, tumour or other foreign body. The appendix is highly populated by lymphoid tissue and the age of highest incidence supports the hypothesis that hyperplasia of this tissue is a trigger for appendicitis.

Obstruction of the lumen leads to bacterial overgrowth and mucous secretion leading to distension and increased pressures, gradually rising above lymphatic and then venous pressures culminating in their obstruction also. This perpetuates the oedema and leads to ischaemia and eventually necrosis (gangrene) of the appendiceal wall.

Given time, a gangrenous appendix will perforate leading to localised peritonitis or an appendiceal abscess if it has been walled off by the omentum, or generalised peritonitis.

Predisposing factors No factors have been clearly identified. Perhaps there is a familial element as well as diets low in fibre and parasitic infections contributing.

Macroscopic & Microscopic appearances The appendix will appear hyperaemic and oedematous in the early stages and then purulent becoming necrotic and often perforated later on in the course of the disease.

Microscopically there will be features of oedema with a neutrophil infiltrate in the mucosa and muscularis layers and possibly signs of necrosis and inflammatory exudates. Occasionally cancer cells are seen to be the cause of the appendicitis.

Clinical features The typical story is of a severe periumbilical (midgut) colicy pain which then becomes constant and migrates to the RIF (involvement of the parietal peritoneum). They will complain of increased pain of movement (peritonism). It is associated with nausea and anorexia and fever. They often also complain of vomiting, diarrhoea or constipation. This scenario normally evolves quickly over 1-2 days.

On examination the patient is often flushed, lying still on the bed with their right hip flexed with pain on straightening it (psoas sign). They may have a low-grade pyrexia and tachycardia. Their abdomen will be tender with peritonism (guarding and rebound tenderness) in the RIF over McBurney’s point. They may also demonstrate a positive Rovsing’s sign. DRE may elicit tenderness on the right and urine dip may show leucocytes (from an inflamed appendix touching the ureter or bladder, note that if nitrites are present this should raise suspicions of an incorrect diagnosis).

The mnemonic MANTRELS is good for remembering the important factors in the diagnosis of appendicitis. It is actually known as Alvarado’s scoring system and can be found on my site.

Elevated WCC and CRP are an aid to the diagnosis but these tests cannot exclude appendicitis.

AXR will not offer anything to reinforce a diagnosis of appendicitis but may highlight other pathology. If acute appendicitis is thought to be the likely diagnosis AXR should not be performed routinely. Erect CXR is also unlikely to be of any benefit in this case.

USS is helpful to rule out gynaecological pathology. CT scanning may also be used to rule out other pathologies such as caecal cancer or other masses. However, both investigations are too insensitive to use as a diagnostic tool for appendicitis although they have a high specificity if appendicitis is diagnosed.

Prognosis Appendicitis can be treated conservatively with antibiotics although this is not particularly effective so appendicectomy is preferred. The group of patients which may benefit from antibiotics are those with appendiceal masses where the omentum has already walled off the infection.

Appendicectomy can be performed open, through an incision over McBurney’s point, or laparoscopically, which is becoming increasingly popular especially amongst those patients there is some doubt over the diagnosis. After operation, the patient can eat and drink immediately and most are discharged within 2-3 days. Patients are not even followed up because the outcome is generally so good. The mortality of appendicitis is about 0.25%.



Source by Nick F Harvey

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