True statements regarding the pathophysiology of acute appendicitis include which of the following:

a. Fecaliths are responsible for the disease process in approximately 30% of adult patients

The most common cause of appendicitis is obstruction of the appendiceal lumen. In young children and young adults, the most common cause of lumenal obstruction is lymphoid hyperplasia from the submucosal follicles which are abundant. Lymphoid hyperplasia accounts for 60% of acute appendicitis in the young. In adults, fecalith formation accounts for approximately 30% of acute appendicitis. There is no known causative relationship of Clostridium difficile or other specific organisms with acute appendicitis. The normal flora of the appendix is consistent with that of the adjacent cecum. Neoplasms of the appendix are rare, occurring in 1% to 1.3% of all appendectomy specimens. Carcinoid tumors are the most common, followed in frequency by benign and malignant mucoceles.