A method for cleaning interior surfaces of a header region of a hemodialyzer includes steps of: introducing an insertion device having an end portion and a shaft through a hemodialyzer plug port so that the end portion of the insertion device is within the header region; rotating the shaft at a speed sufficient to generate mechanical stresses for the removal of contaminants from interior surfaces of the header region; removing the insertion device from the header region; and rinsing and flushing away the removed contaminants from the header region. An apparatus and an insertion device for cleaning a header region of a hemodialyzer are disclosed.