I have never encountered a bent axle but have seen bent flanges from :Curb checking after sliding on ice or big pot holes while carrying a load or someone backs into your truck and the bumper just pushes the wheel. All can bend a flange or wheel or deform the drum. If you realy think its the axle use a long enough machined straight edge and feeler gauges, the gap wont lie. If its bent be concerned about the axle tube and stress on the differential.
