Thank you for your question. My name s Dr. Stacy. I have been a small animal veterinarian for 14 years and I'd like to help with your question.
The lack of bladder and bowel control is definitely something we can see with nerve or spine damage... does the tail move normally or does it seem king of 'limp' too? Sometimes they also have trouble with weakness or incoordination in their rear limbs. The nerve damage can be caused by a number of things. It can even be a deformity that they are born with, but often is causes by trauma... either being struck by a car or picked up or pulled by their tail.
Usually the weakness is permeate, but sometimes they will have small improvements over time. These kinds of problems are difficult because the cat may be otherwise healthy, however the incontinence can cause all kinds of problems. First, you can't really have the cat in the house because of the mess it will make. However, these cats shouldn't be outside because they can get severe scalding and infection from the fecal matter on their bottom and the urine on their legs. This can lead to fly strike and even maggots. They also can't escape predators well if they are left outside. If you have a place that you can keep her and she is eating and drinking and otherwise feeling fine, then you can try to manage her problem. You pretty much just need to clean her daily so that she doesn't get an infection. You can use baby wipes or just warm water. If she already has an infection in the area she may need antibtiotics. She will always be prone to bladder and skin infections.
I would say, feed her good food and add some probiotics to it (I like fortiflora). And see if she gains weight. And if you think you can care for her, then give it a try. If you know you can't care for her or if she is sick then consider having her put down so she doesn't have to suffer.
I hope that helps, but if you have more questions let me know. If not, please rate my answer.