Acute appendicitis - Disorders of the small bowel and appendix

Disorders of the small bowel and appendix

Acute appendicitis

Definition

Inflammatory disease of the appendix, which may result in perforation.

Incidence

Commonest cause of emergency surgery of childhood (3–4 per 1000).

Age

Any age but usually over 5 years.

Sex

No sex predisposition.

Geography

Disease of Western civilisations.

Aetiology/pathophysiology

Acute appendicitis typically commences with colicky pain suggesting that obstruction of the lumen may be a factor, e.g. by lymphoid hyperplasia, faecoliths, adhesions, fibrosis or neoplasia. The pain is initially felt in the periumbilical region due to the pattern of visceral innervation, but becomes localised to the right iliac fossa as the parietal peritoneum becomes inflamed. Accumulation of secretions result in distension, mucosal necrosis and invasion of the wall by commensal bacteria. Inflammation and impairment of blood supply lead to gangrene and perforation. Once perforation has occurred there is migration of the bacteria into the peritoneum (peritonitis). The outcome depends on the ability of the omentum and surrounding organs to contain the infection.

Clinical features

This is a classic cause of an acute abdomen. Pain is initially periumbilical, then migrates to the right iliac fossa. There is mild to moderate fever, nausea and anorexia. Vomiting is uncommon. The presentation may be less specific in the young, pregnant and elderly. Development of the disease may be over hours to days partly depending on host resistance.

Once there is peritonitis, the patient will have severe pain, exacerbated by movement and has a rigid abdomen with tenderness and guarding over the right iliac fossa. A mass may be felt through the abdominal wall or rectally particularly if the omentum is wrapped around the appendix, or an abscess has formed.

Macroscopy

The appendix appears swollen and the surface vasculature is yellow. There is a rough, yellow, fibrinous exudate on the surface.

Microscopy

Initially there is acute inflammation of the mucosa, which undergoes ulceration. There may be pus in the lumen. As the condition progresses the inflammation spreads through the wall until it reaches the serosal sur face. There is then necrosis within the wall and a site of perforation may be seen.

Investigations

There are no diagnostic tests. FBC may show a raised white cell count, CRP may be raised. Ultrasound is increasingly being used but does not exclude the diagnosis. CT of the abdomen or laparoscopy may be indicated if another diagnosis is suspected. In women of childbearing age a pregnancy test should be performed to exclude an ectopic pregnancy.

Management

Conservative treatment has little place, except in patients unfit for surgery. Fluid resuscitation may be required prior to surgery and intravenous antibiotics are commenced.

·        Under general anaesthetic the abdomen is opened by an incision along the skin crease passing through McBurney’s point (one third of the distance from a line drawn from the anterior superior iliac spine to the umbilicus). The muscle fibres in each muscle layer are then split in the line of their fibres (grid iron incision). The mesoappendix is divided with ligation of the appendicular artery. The appendix is ligated at its base and removed. The stump is invaginated with a purse string suture. Peritoneal washout is performed if there is pus in the abdomen. The wound is then closed in layers.

·        If there is an appendix abscess this should be surgically drained.

Discovery of a normal appendix means other pathology must be excluded (i.e. convert the operation to a diagnostic laparotomy). In most cases, the appendix is removed to avoid confusion if patients ever represent with an acute abdomen.

Prognosis

Uncomplicated appendicitis has an overall mortality of 0.1%. Mortality rates may be as high as 5% following perforation.