Postoperative black stool may be a symptom caused by gastrointestinal bleeding, or it may be caused by intestinal endotoxin deposition caused by stool stagnation, so you need to check your stool routine before treatment.

Suggestion:

In other words, a fecal occult blood test is needed to rule out any abnormality. If the abnormality is true, it is related to your gastrointestinal bleeding. If it is negative, it is related to the accumulation caused by postoperative fecal obstruction. Pay attention to improving diet or related to taking iron supplements.