Brief Answer:

As detailed below.

Detailed Answer:

Hi,

Since the Cyst on pancreas is benign, it may not cause black stools unless transformed into malignancy or bleeds and the blood comes to duodenum causing black stools.

Black stools are due to high iron content of blood and also can occur if one consumes anything that has high iron contents.
Most important is to get the stool tests done to see whether the black color is due to blood or not.

The commonest causes of black stools area as follows:
Peptic ulcer of stomach or duodenum.

Bleeding from angiodysplasia or anything that can cause bleeding.
Blood thinning medications.

Medications that cause gastritis.

Hence I would advise you the following in such a situation:
Get the stool tested.

Consult your Doctor and get an appointment with a Gastroenterologist for clinical evaluation, examination and most important the investigations.

Upper GI Endoscopy, colonoscopy, Enteroscopy if required and is available.

CT scan of abdomen. Tests of blood for CBC, bleeding/coagulation times, prothrombine time, liver function tests and as advised.
All these help to get a probable cause and thus get treated according to the cause thus found.

Hope I have answered your query.

Take care

Regards,
Dr T Chandrakant, General Surgeon

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