L5-s1 disk herniated and cauda equina , did surgery 4 months before.my bladder not empties so urologist thinks still be nerve compression. is that so?

Maybe, maybe not: Acute cauda equina syndrome from a ruptured disk in the low back is an urgent problem & is best treated with surgery. However, not everyone gets better. Residual numbness in the private area and difficulties with bladder emptying can remain despite surgery. It is something to discuss with your spine surgeon. She and he can assess, seeing if you need further tests like an mri.

Speak to your : Surgeon about repeating a MRI with contrast to evaluate surgical outcome to make sure adequate decompression and no recurrence or new disc issue. Sometimes , there may be ongoing issues that may or may not be permanent and a urodynamics test may help to evaluate this situation further if MRI is negative.