Can the first symptom of appendicitis be diarrhea?

Yes: Yes, even though classical presentation starts with anorexia and periumbilical pain, diarrhea may be the first symptom, especially in children.

Unlikely: Appendicitis causes pain because the opening of the appendix is blocked, causing pressure inside the appendix that first causes mid-abdominal pain. As the wall of the appendix stretches and the blood flow decreases, bacterial infection and inflammation causes irritation and the pain localizes to the area around the appendix. Diarrhea is caused by fluid production by the intestine or colon.