Hello,
Black stools are likely due to an upper gastrointestinal problem since bleeding due to hemorrhoids would manifest as fresh blood.
In particular, stomach ulcers or erosions which bleed can cause
abdominal pain, and since blood is an irritant to the gastrointestinal tract, it can then cause
diarrhea.
On the other hand, the color of food can also affect the stool color, but would not cause the symptoms of pain, diarrhea, or
constipation.
I suggest a consult with a gastroenterologist for proper diagnosis and management depending on her presenting symptoms and examination findings, as this will dictate whether she may only take medications or would require
endoscopy.
But if she'd have persistent bleeding or black stools, which may cause
anemia, I suggest an Emergency room consult and admission for observation. She might as well be referred to a gastroenterologist as an in-patient.
Hope I have answered your query. Let me know if I can assist you further.
Take care
Regards,
Dr Daryl Derick B. Dizon, General & Family Physician