Rule outs for glomerulonephropathy include:

infectious:

-chronic bacterial infection (pyometra, endocarditis, brucellosis,
leptospirosis, etc)
-viral (canine adenovirus I)
-tickborne diseases (RMSF, ehrlichia, Lyme)
-parasitic disease (esp heartworm aka dirofilaria immitis; leishmania)

neoplastic:

-any neoplasia; multiple myeloma in particular can cause amyloidosis

immune mediated:

-lupus
-pancreatic necrosis
-anti-glomerular basement membrane antibody (as in humans)
-systemic inflammatory response syndrome

other:

-long term cushing's disease or high dose steroids
-familial (amyloidosis of Shar Peis, others)
-idiosyncratic/idiopathic

Treatments include:

-elimination of offending antigen if possible (rare)
-immunosuppressive therapies: cytoxan 50 mg/m2 q 48 hrs, azothioprine
(dogs only) 50 mg/m2 PO SID or EOD, cyclosporine (dogs only) 15 mg/kg PO
SID
-moderately protein restricted diet of highly digestible protein (cottage
cheese, egg white)
-reduced sodium intake & diuretics to induce negative sodium balance and
drain excessive fluid. Furosemide (lasix) 2-4 mg/kg SID-TID until edema is
resolved.
-prevent systemic hypertension using diuretics, salt restriction,
beta-adrenergic blockers, vasodilators - esp enalapril (ACE inhib) to
change interglomerular pressure and reduce protein losses.
-aspirin to prevent thrombosis due to decreased AT-III.