Do all hernias produce protrusions or bumps?

No they do not: While protrusions and bumps are often a common sign of a hernia they do not always occur. A hernia is a tear in the wall of the abdominal muscle. Depending on the location and size of the tear some of the underlying fat and/or portion of the intestine may poke through, this is what causes a bump. If nothing poke through the tear then you will not have a bump, but still have a hernia.