My nerves were pressed due to disk herniation, did surgery but bladder function hasn't come back.my surgeon is doing nerve conduction test. why is that?

Need further testing: Return of bladder function depends on the amount of time the function was affected prior to surgery, it also depends on adequate decompression of the nerves of the cauda equina. You should speak to your surgeon urgently and may need repeat MRI to make sure the compression is gone and possibly even urodynamics study to further elucidate the problem. Hope this helps.

ReinnervTion: May be looking for early electrical signs of re-inervation im sorry for your affliction.