Holding the act of defecation has not been shown to cause appendicitis. The most common cause of appendicitis is a FECALITH. This is nothing but fecal material that has hardened inside the lumen of the appendix causing a small obstruction. Having a fecalith may be due to a prolonged transit time of fecal material in the colon due to many other factors such as a low fiber diet, megacolon, etc. A fecalith is not associated with "pag-pipigil ng dumi". When we hold our defecatory movement, the feces is already in the rectum, way past the appendix. The act of defecation is inevitable, even if you hold your bowel movement for the moment, there will come a time that it has to come out. This is an involuntary reflex and no one can effectively hold his or her bowel.
So, do not have sweat it out with your feces. It is naturally a no brainer activity of daily living. You may move your bowels as you please, no rush.