You can look at your symptoms two ways; what can cause bladder problems and what symptoms the pathology the MRI revealed can cause.
Bladder incontinence or hesitation can be caused from the spine but normally from a compression of the spinal cord or of the cauda equina (the nerve that live in the lower back). Spinal cord compression causes many more symptoms than you are experiencing (see myelopathy under conditions) and cauda equina syndrome (normally caused by a massive disc herniation which you don’t have) would cause more symptoms than you describe.
Pain can cause bladder dysfunction, especially in women who have delivered babies as a cystocele can have formed (stretching of the pelvic diaphragm). That needs to be diagnosed by a urologist or an OB/GYN.
The herniation you have at L5-S1 is causing “fairly severe lateral recess and moderate foraminal encroachment on the left side” according to the radiologist. This compresses the L5 or S1 nerve on that side and can cause buttocks pain that radiates down to the foot associated with paresthesias (pins and needles) possibly increased with sitting or bending forward.
If you have no weakness in your leg and the leg pain is mild or tolerable, an injection might help to break the pain cycle. According to the radiologist, there is no significant canal stenosis which means you do not have cauda equina syndrome. See section on “when to have lower back surgery” for more information.
Ask your primary care physician if you can get a referral to a urologist. Also, a second opinion from an interventional PM&R doctor or a spine surgeon might be helpful. You can also wait and get the opinion from the neurosurgeon.