Ampulla of Vater – Wikipedia

Thomas’ sign is the production of silver stools and can be indicative of cancer of the Ampulla of Vater. The silver colored stool is a combination of the white stool of obstructive jaundice combined with black stool of melena or bleeding. It was first described in the British Medical Journal by Dr. H. Ogilvie in 1955.

https://en.wikipedia.org/wiki/Ampulla_of_Vater