Saggy anal skin with bump

Hello, I was given a 2 year old, neutered chocolate lab, along with his brother. I’ve never seen a dogs butt look like this, is it normal? Wherever he sits with his butt, it smells rancid. He behaves normally.

Hello - I'm afraid that this doesn't look at all like a normal dog's bottom to me from this angle.  I wondered about cancer, previous surgery or long standing developmental issues but to be honest, would want to examine the patient in context, the correct way up in order that I could understand where the limbs and tail were, and perhaps examine the area before passing comment.  Is he able to deafecate normally?  Are testicles present?  Please do show this bottom to your vet in order to make a plan from here.