When was the last time he had a full geriatric blood profile done? You should have one done every year for a senior and a "mini" CBC in between. It can alert your vet to anything that might be starting and can prolong his life.
He may just have doggie Alzheimer's called Cognitive Dysfunction Syndrome (CDS), but it's important to rule out something else causing his disorientation.
This article has a lot of good information on the condition:
Doggy Alzheimer's Disease - Dogs