I'm 37 years old have spina bifida occulta which has never really caused much grief except for kidney failure now have numbpatch on leg, tethered cord?

Not likely. A tethered cord may be a problem during periods of rapid growth during childhood. As an adult, it is very unlikely to start causing a problem. Minor numbness is common in normal persons and may be a trapped or pinched nerve. Tight clothing may be a cause or pelvic problems including inflammation of kidney or uterus or ovaries, etc. Discuss this with your doctor. May need pelvic ultrasound.