Images of Memorable Cases: Case 6 Stool specimen from a patient with epigastric pain, jaundice, and anemia. 6. Silver stool A tarnished-silver or aluminum paint-like stool color characteristically results when biliary obstruction of any type (white stool) combines with gastrointestinal bleeding from any source (black stool). This patient had carcinoma of the ampulla of Vater, the most frequently cited cause of silver stools.