Acute appendicitis is acute inflammation and infection of the vermiform appendix, which is most commonly referred to simply as the appendix. The appendix is a blind-ending structure arising from the cecum. Acute appendicitis is one of the most common causes of abdominal pain and is the most frequent condition leading to emergent abdominal surgery in children. The appendix may be involved in other infectious, inflammatory, or chronic processes that can lead to appendectomy; however, this article focuses on acute appendicitis.
The vermiform appendix is generally 5-10 cm in length. It arises from the cecum, which in most children is located in the right lower quadrant of the abdomen.
Although the base of the appendix is fixed to the cecum, the tip can be located in the pelvis, retrocecum, or extraperitoneum. Note that the anatomic position of the appendix determines the symptoms and the site of tenderness when the appendix becomes inflamed.
Once the appendix becomes obstructed, bacteria trapped within the appendiceal lumen begin to multiply, and the appendix becomes distended. The increased intraluminal pressure obstructs venous drainage, and the appendix becomes congested and ischemic.
The combination of bacterial infection and ischemia produce inflammation, which progresses to necrosis and gangrene. When the appendix becomes gangrenous, it may perforate. The progression from obstruction to perforation usually takes place over 72 hours.
During the initial stage of appendicitis, the patient feels only periumbilical pain due to the T10 innervation of the appendix. As the inflammation worsens, an exudate forms on the appendiceal serosal surface. When the exudate touches the parietal peritoneum, a more intense and localized pain develops.
If the contents become walled off and form an abscess, the pain and tenderness may be localized to the abscess site. If the contents are not walled off and the fluid is able to travel throughout the peritoneum, the pain and tenderness become generalized.
Acute appendicitis is due to obstruction of the blind ending appendix, resulting in a closed loop. In children, obstruction usually results from lymphoid hyperplasia of the submucosal follicles. The cause of this hyperplasia is controversial, but dehydration and viral infection have been proposed. Another common cause of obstruction of the appendix is a fecalith.
Rare causes include foreign bodies, parasitic infections (eg, nematodes), and inflammatory strictures.
Other studies, such as interleukin 6 and C-reactive protein (CRP) assays, have been advocated by some in the diagnosis of appendicitis. However, in multiple clinical series, these studies have not been shown to be of clear benefit and, for the most part, only add to the cost of the evaluation.
Treatment and Management
Given that patients with possible appendicitis may have an equivocal history and physical examination findings and inconclusive supporting test results, the following measures are key to any evaluation and treatment plan:
Relieve the patient’s pain and discomfort early and consistently
Communicate with the patient and family about the plans
Repeat the examination often
Adjust the differential diagnosis as appropriate
Keep the patient for observation if a firm diagnosis is not made or for follow-up.