A 60-year-old male truck driver with a 30-year smoking history presents with edema, oliguria, and progressive renal dysfunction over 1 month. One month ago, his BP was 160/95 mmHg, UA showed PRO(+++), RBCs 15-20/HPF, Cr 168 μmol/L, BUN 9.5 mmol/L, and CBC revealed mild anemia. Diuretics provided no significant edema relief. At our clinic, repeat tests show BUN 19.6 mmol/L and Cr 388 μmol/L. What is the most likely diagnosis?