Yes, ENTEROSTOMY is a Scrabble word!

Letter values in Scrabble US: E 1, N 1, T 1, E 1, R 1, O 1, S 1, T 1, O 1, M 3, Y 4.

Is it a valid word?

ENTEROSTOMY is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

surgical operation that creates a permanent opening through the abdominal wall into the intestine

Not playable in Scrabble US: ENTEROTOMY.