What is the actual prognosis for renal artery occlusion?

Usually stable: Usually it is a slow process allowing the development of collateral circulation i.e. Side branches that bypass the occlusion. The kidney is already shrunken with poor function in most of the cases. But with stable function. Occlusion usually is not openable. Accordingly, deterioration of already poor kidney function is not aggrassive. Check with your doc about the other kidney condition. However!

Atrophy: If the vessel is truly totally occluded the kidney will shrink or atrophy. As long as the other kidney is ok, you should be too. See a good nephrologist and endovascular suegeon.