What is the natural history of appendicitis?

From the Guidelines

The natural history of appendicitis is characterized by a progression from simple inflammation to suppuration, gangrene, and eventually perforation, with a mortality rate of less than 1% for non-perforated appendicitis, but rising to 5% or higher with perforation, particularly in elderly patients or those with comorbidities. The progression of appendicitis can be divided into three stages: a normal appendix, uncomplicated acute appendicitis, and complicated appendicitis, according to their macroscopic and microscopic appearance and clinical relevance 1. Without treatment, appendicitis progresses through several stages, with perforation typically occurring 24-36 hours after symptom onset, leading to either localized abscess formation or diffuse peritonitis, depending on the body's ability to contain the infection. The high morbidity and occasional mortality associated with acute appendicitis are related to delay in presentation by patients or delay in diagnosis by the clinician, which may result in complications like gangrene, perforation, appendiceal mass, and peritonitis, all of which would prolong hospital stay and increase the cost of treatment 1.

Some key points to consider in the natural history of appendicitis include:

• The incidence of acute appendicitis varies, with a low incidence rate in sub-Saharan Africa and many regions of Asia and Latin America, but appears to be increasing in many urban centers and low- and middle-income countries (LMICs) 1.
• The clinical presentation of appendicitis is often inconsistent, with atypical presentations resulting in delay in treatment, and diagnostic scoring systems have been developed to provide clinical probabilities that a patient has acute appendicitis 1.
• The mortality rate for non-perforated appendicitis is less than 1%, but rises to 5% or higher with perforation, particularly in elderly patients or those with comorbidities, with a higher risk of perforation in elderly patients due to vascular sclerosis and narrowing of the lumen by fibrosis 1.
• Rarely, appendicitis may resolve spontaneously through a process called "spontaneous resolution," but this is unpredictable and not a recommended management approach, with the definitive treatment for appendicitis being appendectomy (surgical removal of the appendix), though antibiotics alone may be considered in select cases of uncomplicated appendicitis 1.

In terms of management, appendectomy remains the treatment of choice for acute appendicitis, with antibiotic therapy being a safe means of primary treatment for patients with uncomplicated acute appendicitis, but with a higher recurrence rate and need for additional diagnostic certainty with a CT-proven diagnosis 1. The role of laparoscopic appendectomy has been established as a safe and effective approach, with benefits including a shorter length of hospital stay, less postoperative pain, and earlier postoperative recovery, but with a slight increase in the incidence of intra-abdominal abscess and intra-operative bleeding 1.

Overall, the natural history of appendicitis is complex and influenced by various factors, including delay in presentation and diagnosis, with a high morbidity and mortality rate associated with perforation, particularly in elderly patients or those with comorbidities, and with appendectomy remaining the definitive treatment for appendicitis, though antibiotics alone may be considered in select cases of uncomplicated appendicitis.

From the Research

Natural History of Appendicitis

• The natural history of appendicitis is characterized by the possibility of spontaneous resolution or the risk of progression to perforation 2.
• Studies suggest that spontaneous resolution of appendicitis is common, and that perforation can rarely be prevented 2.
• The risk of perforation has been exaggerated, and in-hospital delay is safe 2.
• The proportion of perforation is a questionable measure of the quality of management of patients with suspected appendicitis and should be used with caution 2.

Progression to Perforation

• Perforation can lead to serious complications, including peritonitis, abscess formation, and death 3.
• Mortality from acute appendicitis is less than 0.3%, but rises to 1.7% after perforation 3.
• Perforation can be complicated by fistula formation, as seen in a case report of a 45-year-old woman with a 7-day history of right lower-abdominal pain and swelling due to perforated acute appendicitis and abdominal wall abscess 4.

Diagnosis and Treatment

• The clinical diagnosis of acute appendicitis is based on history, physical examination, laboratory evaluation, and imaging 5.
• Laparoscopic appendectomy remains the most common treatment, but increasing evidence suggests that broad-spectrum antibiotics can successfully treat uncomplicated acute appendicitis in approximately 70% of patients 5.
• Specific imaging findings, such as appendiceal dilatation or presence of appendicoliths, can identify patients for whom an antibiotics-first management strategy is more likely to fail 5.
• Treatment of appendicitis is by appendicectomy after appropriate fluid resuscitation, analgesia, and intravenous antibiotics, with laparoscopic appendicectomy being better than open appendicectomy in most cases 6.