Some older dogs do lose the control of their bowels as they age.
Incontinence including bowel incontinence and loss of bowel control is common and normal in some older dogs as they near the age at which they are gonna die.
Not all dogs when they get older will lose their bowel control or bladder control but it is possible and there's not too much that can be done.
If your dog is getting older and nearing the end of it's life then loss of bowel control and loss of bladder control is a common sign that the dog is nearing death.
Dogs have a pretty short life when it's compared to a human lifespan.
Most dogs die within 10 to 20 years depending on the size of the dog.