Have you seen a Neurosurgeon about the bulging discs? Bulging discs can cause pain, numbness, foot drop and other Neurological symptoms. If you haven't seen a Neurosurgeon about your bulging discs then I would recommend doing so as soon as possible.
A Lumbar MRI is not used to detect lesions in MS but to rule in/out back problems such as what was found in your case. The most common MRIs ordered for MS is the brain and cervical (neck) but sometimes the thoracic (mid back). Those same MRIs can also show back problems, if any.
Best wishes on your appointment with the Nephrologist. Medications, over the counter and prescription, can cause blood work for kidney function to be out of the normal range.
Diagnosed with Multiple Sclerosis in 1985
PTSD diagnosed Feb 2004 (PTSD since age 2), Anxiety/Panic attacks secondary to PTSD.