appendagitis is basically where fleshy finger shaped growths on the outside of the large intestines called appendages get infected or inflamed. these appendages aren't entirely understood. they may serve as padding in the abdominal cavity but when they are inflamed they can cause trouble. appendagitis is a legitimate medical condition but a gi doctor is more likely to know what it is. the exploratory surgery is probably to find out the size and location of these appendages and possibly to remove them. the colonoscopy could come out normal looking because the appendages are on the outside of the large intestine not the inside. as for your friend's symptoms they all lead to each other. appendagitis could cause all the things you mention.
what causes pain nausea and blockage in the colon/abdomen? . i know a college aged person who has been suffering from pain and nausea. the doctors mentioned "appendigitis" (not appendicitis). she was hospitalized for days but then seemed to get better. however she is now having the same symptoms again. she is going to have exploratory surgery. she had a recent colonoscopy which showed no problem. have you heard of appendigitis? no one in the medical profession that i know seems to know what it is. in fact they have never heard of it!