Vitamin C acid in oranges causing pain: Why?

Acids in oranges:
https://www.livestrong.com/article/529727-the-acid-in-oranges/
As you will see, there are several. However I don't know which, if any, pass through the gut unmodified, and if they are unmodified, are they possibly irritating your cancerous tissue? Or, is it just as likely that the body/liver modifies them and it is in the modified state that your cancerous tissue becomes irritated enough to make nerves nearby complain? And which of the several listed is to blame, or are several of them to blame, maybe all of them?

Perhaps the easy solution is just to forego oranges? Try Kiwi fruit. They're amazing and wonderful for the body. I eat mine, skin and all. The skin is fuzzy-ish, but tasty and slightly sour. Just lop off both ends of the fruit because the core is hard and unpleasant.