IVB is more like a really bad arthritis though I could not find a conclusive report on what actually causes it or if it could indeed be a result of bad breeding. http://www.medscape.com/viewarticle/543611
Our last Lab girl had it, along with significant spinal spondylosis, which is arthritis. She was diagnosed after an acute episode of pain at age 12.5 and lived a happy life till age 14.5. She lost some fecal control, whether from the ailment or the pain meds we are not sure, but not urinary control, which would have been a lot messier in the house.
Good muscle support in the back is very important and if at all possible an exercise regime should be kept up, if possible. Swimming is good but we just cut our skiing and hiking outings in half (making them one hour instead of two). As time went on they got shorter and shorter, but more in a day till we were going out for 20 or 15 or 10 minutes, 2 or 3 times a day, plus around our own yard. We discovered the two acre park behind our house which I had previously never walked around because it was so small.
WE did lift her in and out of the jeep and she stopped going up and down the stairs in our house. REally and truly, I think the ailment that had a much sadder and more profound effect on her enjoyment of life was her increasing deafness. We could medicate for pain, and were using very strong meds at the end. But we could do nothing for the deafness. It was so isolating for her, coupled with being unable to go anywhere in the house she wanted. I think loneliness, between the three health problems, was the worst to deal with.