What is the difference between a disc bulge and slipped disc (disc herniation)?

Usually, "disc bulge" in a radiologist's report describes disc herniation. It is a small disc protrusion due to the natural ageing process. More serious/larger disc protrusion or extruded disc are called "slipped disc" which will require surgery as treatment. "Disc bulge" is used due to a lack of universal standard term to describe this condition.