What is Appendicitis?
Appendicitis is an inflammation of the appendix, a small, tube-like structure attached to the cecum of the large intestine. The condition is a common cause of acute abdominal pain and often requires surgical intervention.
Histological Structure of the Normal Appendix
The normal appendix is composed of several layers: the mucosa, submucosa, muscularis propria, and serosa. The
mucosa features an epithelial lining with goblet cells and lymphoid tissue, which plays a role in the immune response. The
submucosa contains connective tissue, blood vessels, and nerve fibers. The
muscularis propria consists of two layers of smooth muscle, and the
serosa is the outermost layer, composed of a thin layer of connective tissue covered by mesothelium.
Histological Changes in Appendicitis
During appendicitis, several histological changes occur: Inflammation: The mucosa and submucosa become infiltrated with
neutrophils, indicating acute inflammation. This infiltration can extend to the muscularis propria and serosa in severe cases.
Edema: The submucosa becomes edematous, and the blood vessels may be congested. This can lead to increased intraluminal pressure.
Ulceration: The mucosal lining may become ulcerated due to the inflammatory process, compromising the epithelial barrier.
Fibrosis: Chronic cases may show fibrosis in the submucosa and muscularis propria as a result of prolonged inflammation and healing processes.
What Causes Appendicitis?
The exact cause of appendicitis is often unclear, but it is generally believed to result from obstruction of the appendiceal lumen. This obstruction can be due to
fecaliths (hardened stool), lymphoid hyperplasia, foreign bodies, or tumors. The obstruction leads to increased pressure within the appendix, decreased blood flow, and subsequent bacterial invasion.
Histological Diagnosis of Appendicitis
Histological examination is crucial for diagnosing appendicitis. A biopsy of the appendix shows infiltration of neutrophils into the layers of the appendix. In cases of perforation, the serosa may display fibrinopurulent exudate. Pathologists look for the presence of neutrophils in the muscularis propria as a definitive sign of appendicitis.Complications Observed Histologically
If not treated promptly, appendicitis can lead to complications such as: Perforation: A perforated appendix can lead to peritonitis, which manifests histologically as widespread infiltration of inflammatory cells and fibrin deposition in the peritoneal cavity.
Abscess Formation: Localized collections of pus can form, characterized by a central area of necrosis surrounded by granulation tissue and inflammatory cells.
Gangrene: Ischemic necrosis of the appendiceal wall can occur, resulting in loss of cellular architecture and infiltration by inflammatory cells.
Histological Differences in Pediatric vs. Adult Appendicitis
While the basic histological features of appendicitis are similar in children and adults, there are some differences: In children, the lymphoid tissue in the appendix is more prominent, and lymphoid hyperplasia is a common cause of luminal obstruction.
In adults, fecaliths are a more common cause of obstruction, and chronic inflammatory changes are more frequently observed.
Treatment and Prognosis
The primary treatment for appendicitis is surgical removal of the appendix, known as an
appendectomy. Histological examination of the removed appendix confirms the diagnosis. If treated promptly, the prognosis is excellent, and most patients recover without significant complications.
