When my girlfriend was still a trainee, she assisted a surgeon in open intestinal surgery, and when the patient’s belly was opened up, this is what they saw:
Bowel infarction (also called “gangrenous bowel”) is caused by insufficient blood flow (and in its turn this can be caused by various vascular issues).
The patient’s bowel was completely blueish-black, and there was nothing they could do.
So they closed the patient, and sent him back to intensive care — they knew there wasn’t even time enough to start up palliative sedation.
He died from severe infection and sepsis shortly after.