A nice way that describes' the breakdown of these disorders : As suggested by Dr.A Bellucci.
Proximal Dysfunction can be:
2.Altered Membrane Transport
3.Altered Intracellular Processes
So lets take them one by one.
1. Volume expansion decreases proximal tubular reabsorption (higher pcP and lower pcP): met acidosis (bicarbonaturia) & low BUN and leading to a physiologic prox tubular dysfunction. A pathologic example of this is renal vein thrombosis
2. Altered membrane transports are the ones that specifically lead to either bicarbonaturias or phosphaturias. Examples of these are: Osteopetrosis, Carbonic anhydrase inhibitor use, tumor induced osteomalacia or too much FGF 23
3. The last one is the ones we always encounter:- Myeloma, Ifosphomide toxicity, Heavy metal toxicity and in children: cystinosis, Dent's Diseases and Lowe's disease.