A 60-year-old man with chronic kidney disease stage 4 presents with bilateral leg edema and dyspnea. Laboratory tests show BUN 60 mg/dL and creatinine 3.5 mg/dL. Urinalysis shows 4 plus protein, and 24-hour urine protein is 5.2 g. Serum albumin is 2.1 g/dL and cholesterol is elevated. Which syndrome best describes his presentation?