What are the primary causes of appendicitis in patients of different age groups and medical histories?

Causes of Appendicitis

Primary Pathophysiologic Mechanism

Appendicitis is primarily caused by obstruction of the appendiceal lumen, which leads to increased intraluminal pressure, bacterial overgrowth, inflammation, and potential perforation. 1, 2

Specific Obstructive Causes

Fecaliths (Appendicoliths)

• Fecaliths are the most commonly identified cause of appendiceal obstruction, present in approximately 36% of acute appendicitis cases 3
• Fecaliths form from inspissated fecal material and can be detected preoperatively via ultrasound, CT, or MRI 3
• The presence of intraluminal fecaliths or appendicoliths on imaging is predictive of perforation, with an odds ratio of 2.47-2.67 1
• When fecaliths are identified preoperatively with clinical symptoms, early appendectomy is recommended to reduce morbidity and mortality 3

Lymphoid Hyperplasia

• Lymphoid hyperplasia is a common cause of luminal obstruction, particularly in younger patients 4, 2
• This mechanism is more prevalent in children and adolescents due to more active lymphoid tissue in this age group 1

Neoplastic Causes

• Colonic and appendiceal neoplasia account for approximately 7% of cases presenting as acute appendicitis 5
• Neoplastic causes include colonic adenocarcinoma (most common malignant cause), mucinous tumors, carcinoid tumors, and endometriomas 5
• Patients with neoplasia-related appendicitis tend to be older (mean age 46.9 years) and present with longer duration of symptoms (mean 12.6 days) compared to typical appendicitis 5
• Cecal carcinoma can lead to appendiceal obstruction and should be considered in older patients 2

Other Obstructive Causes

• Parasites, undigested plant residues, and foreign bodies can cause luminal obstruction 3
• These causes are less common but should be considered based on patient history and geographic location 3

Age-Related Differences in Etiology and Presentation

Elderly Patients (≥65 years)

• Elderly patients have significantly higher rates of complicated appendicitis (18-70%) compared to younger patients (3-29%) 1
• Vascular sclerosis of the appendix, luminal narrowing from fibrosis, and fat infiltration of muscular layers create structural weakness predisposing to early perforation 1
• Neoplastic causes are more common in this age group, requiring higher index of suspicion 5
• Diagnostic accuracy is lower in elderly patients (64%) compared to younger age groups (78%), contributing to delayed diagnosis 1

Pediatric Patients

• Lymphoid hyperplasia is the predominant cause in children and adolescents 1, 4
• The lifetime risk of appendicitis peaks between ages 10-30 years 1

Pregnant Patients

• The same obstructive mechanisms apply, but anatomic displacement and physiologic changes complicate diagnosis 1
• Appendicitis is the most common nonobstetric surgical emergency during pregnancy 6

Clinical Implications by Cause

Fecalith-Associated Appendicitis

• Higher risk of perforation and complications 1, 3
• CT findings of intraluminal fecaliths have sensitivity of 55.4% and specificity of 68.3% for predicting perforation 1
• Extraluminal appendicoliths indicate perforation with odds ratio of 28.9 1

Neoplasia-Associated Appendicitis

• Longer symptom duration before presentation (mean 12.6 days vs. typical 1-3 days) 5
• Older patient age (mean 46.9 years) 5
• May require right hemicolectomy rather than simple appendectomy if malignancy confirmed 5

Geographic and Demographic Variations

• Lifetime risk varies by geography: 9% in USA, 8% in Europe, and 2% in Africa 1
• Incidence rates in developed countries range from 5.7-50 per 100,000 inhabitants per year 1
• The incidence has been declining steadily since the 1940s in developed nations 1

Common Pitfalls in Diagnosis

• Do not assume all appendicitis has the same cause—older patients with prolonged symptoms require evaluation for neoplasia 5
• Fecaliths can be present in asymptomatic individuals, so their presence alone does not confirm appendicitis without clinical correlation 3
• In elderly patients, delayed presentation and atypical symptoms often result from the same obstructive mechanisms but with accelerated progression to perforation due to vascular changes 1
• The absence of visualized fecalith on imaging does not exclude appendicitis, as lymphoid hyperplasia and other causes may not be radiographically apparent 1