What is the significance of his kidneys?
Rashi: They think all his thoughts.
Radak #1: They are the beginning of thought. The kidneys counsel, and the heart concludes. You acquired 1 them - how can their counsel be hidden from You?!
Radak #2: They are the first creation in man's body. They are like two spokes of a wheel.
Radak: This is like "Koneh Shamayim va'Aretz" (Bereishis 14:19).
What is "Tesukeni"?
Rashi: Tesukekeni (You cover me).
Why does it mention "b'Veten Imi"?
Radak: It is a place of darkness; there is no light there. There You formed me, and interconnect me with bones and sinews. How can You not know all hidden matters?!
Malbim: This shows that Hashem's knowledge [of his thoughts] is not sensory.
