Imma call it

I lowkey think lil bro has either appendicitis, internal bleeding of the GI tract due to ulcers, masked viscus perforation of any of his abdominal organs (most likely appendix or his bowel), or even pancreatitis. Any of these conditions can be exacerbated by his routine medication, which I think are anxiety, depression, and/or insomnia meds. Those medications fall under a greater class of drugs called SSRI/SNRIs that basically fuck with your platelets' ability to form clots (part of blood) and that put you at a much greater risk for internal bleeding. If your platelets are compromised because of a medication, it can cause the holes in your intestines and blood vessels to not get patched up and so they get bigger and then you're fucked. All of these will also cause low hemoglobin count and inflammatory marker hits because they can all induce infection and basically contents that are supposed to be contained are getting exposed to parts of the body that shouldnt normally happen.

My top guess is a peptic ulcer that was exacerbated by his medication because they didn't immediately rush Dohu into surgery. If it was acute appendicitis, they usually have the patient undergo surgery right away. Instead, they're admitting him for a few days to run tests, which a peptic ulcer can be diagnosed in those few days and it's harder to catch right away. Appendicitis has like very distinct symptoms that weren't mentioned, but it's not off my list completely. Just wish we knew what kind of meds he was on tho so I could come up with a better guess.