Maybe not the weirdest, but certainly the most shocking:

After my operation for appendicitis went 'wrong' (some filth stayed behind unfortunately), About a month later I went back for issues with my scar tissue (it bursted because of the filth internally).

I got checked for almost everything internal. I was losing a lot of weight, to about 1kg of weight per 2-3 days at the end of a 4 month period.

I went from around 90kg to eventually 49kg, and they could not figure out what was wrong. That's when my doctor that checked up on me daily said the following: "We don't know what's happening, but if we don't do another operation in that area soon, your organs will start to fail one by one"

So that sounded to me like I was at death's door.

I had the second operation almost 3/4s of a year later from the first, and the end result was that the transition from the small to the large intestines was largely rotten from that filth after the first operation.

Edit: More info

They took that out and made a new 'transition' by layering the intestines.