I have severe hemorrhoids where flesh comes out of my anus. When I make Istinja’ water is applied to it. Then I push it into my anus manually. Will this break my fast? What about my past fasts?
In traditional texts, rectum and intestines have been considered as a valid bodily cavity. Contemporary scholars have more detail about the rectum being considered as a valid bodily cavity. Some have considered the upper 2/3rd of it as a valid cavity which can absorb nutrients, while lower 1/3rd cannot. Others have considered that it does not have direct reach towards the stomach, which is the original cavity in regard to fast.
A cautious approach still demands that one should avoid inserting any external substance like water, gel or suppository into the anal cavity that could invalidate the fast.
Insertion of the hemorrhoids back into anus along with wet water will thus invalidate the fast. One should instead use a tissue to dry it out and then insert it.
Since the genuine difference of opinion exists, there is no need for making up past fasts in which you may have done so. But if you have strength and zeal, making up those fast would be cautious and a sign of Taqwa.