If there's no obvious reason for a black stool (such as food, a supplement, or a medication like Pepto-bismol), it could be time to look for blood in the stool. 1  A variety of medical reasons can cause black stools that are also tarry with a foul smell.
1 Lungs, kidneys or liver. Inflammation may cause pneumonia, bronchitis or other problems in your lungs; may lead to problems with kidney function; and may cause hepatitis or cirrhosis in your liver.  Lymph nodes. A small percentage of people with Sjogren's syndrome develop cancer of the lymph nodes (lymphoma).
Certain medications, chemicals, toxins or substances may possibly be underlying causes of Sjogren's Syndrome. Side effects of medications, or exposure to toxins, chemicals, or other substances may cause a symptom or condition. Hence, they become possible underlying causes of Sjogren's Syndrome but are often misdiagnosed or overlooked as a cause.