Acute Appendicitis

Overview
  • Acute inflammation of the appendix is a medical emergency that often requires immediate abdominal surgery. Although acute appendicitis can occur at any age, there is a peak of incidence in the second and third decades.
Pathogenesis
  • The pathogenic sequence ultimately leading to acute appendicitis is thought to be caused by obstruction of the appendiceal outlet, most likely by a fecalith in the majority cases. Although obstructed, appendiceal mucosa will continue producing mucus which accumulates and overtime generates large intraluminal pressures. Rising pressures first lead to venous and then arterial collapse, thus compromising flow of blood to the appendix and ultimately ischemia. The ischemic context proves ripe for bacterial invasion and proliferation of the appendiceal wall which can compromise its integrity and potentially yield bowel perforation.
Morphology
  • The morphology of acute appendicitis is a classic example of acute inflammation characterized by widespread and transmural neutrophilic infiltration. As inflammation and infection progress the situation can appropriately be termed an abscess and given the ischemic context begins to evolve into gangrenous necrosis.
Clinical Consequences
  • Acute Appendicitis is initially characterized by a vague periumbilical abdominal discomfort as sensory information of early distension of the appendix is carried by visceral nerves. However, once inflammation traverses the appendiceal wall, irritation of the peritoneum and peritonitis develop, resulting in activation of somatic nerves. This results in the vague periumbilical pain evolving into severe abdominal pain localized to the right-lower-quadarant, classically at "McBurney's Point". Abdominal pain is accompanied by nausea, vomiting, and severe anorexia which typically manifests as a complete and total lack of appetite. Mild-to-moderate fever and a neturophilic leukocytosis are common, consistent with an inflammatory and infectious pathogenesis. As the appendiceal wall weakens, bowel perforation or fistulization with a distant alimentary segment may occur.