A 30-year-old male presents with 2 years of dizziness and fatigue. Blood pressure is 160/100 mmHg, no edema, hemoglobin 80 g/L, urine specific gravity 1.014, urinary protein (++), granular casts 0-2/HP, BUN 16.4 mmol/L (46 mg/dL), serum creatinine 309.4 μmol/L (3.5 mg/dL), CO2CP 22 mmol/L (50 VOL%). Fundoscopy shows narrowed and tortuous retinal arteries. The most likely diagnosis is: