Pathophysiology
Obstruction is a fundamental factor in the development of
acute appendicitis. Obstruction increases intraluminal
pressure leading to ischaemia, bacterial invasion, bacterial
overgrowth, necrosis, and perforation.
In the early phases, activation of receptors in the
intestinal wall leads to perception of pain in the
periumbilical region. In later phases, when the purulent
secretion from the appendiceal wall contacts the parietal
peritoneum, somatic pain fibres are triggered and the pain
localizes near the appendiceal site, McBurney’s point. The
characteristic organisms responsible of appendiceal
inflammation are predominantly anaerobic, including
Escherichia coli, Enterococcus, Bacterioides fragilis,
Pseudomonas, Klebsiella, and Clostridium5.
Many terms have been used to describe the pathologic
stages of appendicitis, from the normal state to perforation.
Only the clinically relevant distinctions of simple
appendicitis (15.4) and complicated appendicitis should be
made.
Clinical presentation
The classic sequence (persistent abdominal pain, fever, and
localized pain on palpation at McBurney’s point) starts with
periumbilical pain, preceded by appetite loss in about
50–60% of children. The main symptom is abdominal pain,
usually beginning as a vague periumbilical pain or mild
gastrointestinal discomfort. After several hours, this pain
gradually migrates to the right iliac fossa. Characteristically
the pain is implacable and is exacerbated by movements and
pressure, making ambulation painful and difficult. A child
with acute appendicitis typically walks bent over and slowly.
Anorexia is a helpful sign. Nausea and vomiting appear after
the onset of pain. If vomiting precedes abdominal pain,
other diagnoses should be considered.
The last symptom in the clinical evolution is fever, which
appears after pain and vomiting, and no more than 1ºC
above normal. Fever higher than 39ºC is usually associated
with complicated appendicitis (gangrenous and perforated).
Symptoms may be influenced by the anatomical location of
the appendix. Pain of a retrocaecal appendix may be in the
flank or back. A pelvic appendix resting near the ureter or
testicular vessels can cause urinary frequency, inguinal or
testicular pain, or ureteral compression with hydro -
nephrosis. Young patients aged 1–4 years, typically show
vomiting and irritability, and draw up their legs to reduce
pain. Other common manifestations include abdominal
distension, diarrhoea, lethargy, and anorexia, together with
fever. In 50% of cases an abdominal mass is detectable on
palpation. The key point in this group of patients is
vomiting.
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