CT scan in appendicitis shows inflamation around the appendix. Also, PID is due usually to either gonorhhea or chlamydia - so you can test you patient for these. Also ever hear of "chandelier sign" in pid - extreme motion tenderness to motion of the cervix/uterus manipulation typically causes patient to "hit the ceiling" Also in HPI appendicitis pain usually starts around umbilicus, and it migrates to McBurney's point... I'm sure there are many other ways to distinguish these 2...