Yes, KIDNEY is a Scrabble word!

Letter values in Scrabble US: K 5, I 1, D 2, N 1, E 1, Y 4.

Is it a valid word?

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

either of two bean-shaped excretory organs that filter wastes (especially urea) from the blood and excrete them and water in urine