Little different, but SIADH and DI are more about free water balance then disturbances in electrolyte absorption/secretion, despite the abnormal sodium lab findings.
Different from what's being discussed above as far as sweating and exertional losses where you're losing electrolytes that need to be replaced.
If my memory serves me correct, it(including electrolyte absorbtion) was all covered under free water in some or another textbook I had to read along the way.
Right down to the number of attached water molecules.