If you don't have a history of 'stress incontinence', which are those little accidents with sneezing, coughing or laughing, it is unlikely that it would manifest with a big gush unprovoked by bearing down stress. Stress incontinence can hit any female after child bearing and doesn't necessarily relate to aging. Young women can even get the problem.

Autonomic neuropathy can present with continence issues, however, one big gush just doesn't sound typical. If you haven't had other leakage issues, a sudden gush seems to be an odd manifestation.

It sounds like your bladder was full and you had no idea it was full, it sounds like the gush was posturally related and that the bladder sphincter was not up to holding back that amount of urine. If you had no sensation that your bladder was full, that is a concern. If you felt you had to 'go' and were just waiting to get to the bathroom that is a different issue.

I can see how you came up with cauda equina, and it isn't off base given your lower back issues. It is always worrisome when things like that happen, and one usually is most concerned with spinal cord compression, and those are urgent situations.

I think a good going over from a doc is in order.