The main causes of acute appendicitis are obstruction of the appendiceal lumen and concurrent infection. The appendiceal lumen is a narrow tube that communicates with the cecum at one end. Obstruction, such as a fecalith, can lead to increased pressure inside the lumen, disturbances in blood flow, damage to the mucosa, and secondary infection. It can also be caused by direct bacterial infection within the appendiceal lumen, leading to acute inflammation. Additionally, repeated diarrhea or constipation and other gastrointestinal dysfunctions can also cause circulation disturbances in the appendix, leading to bacterial invasion and acute inflammation.