A 26 year old man has nausea and fatigue for the last week. He had a sore throat 6 weeks ago treated with a short course of oral antibiotics. He has no past medical problems and does not take any regular medication. He smokes 10 cigarettes per day and only drinks socially. Blood pressure is 167/94 mmHg. 

Investigations:

                     Last Year         Now 
Sodium             138              145          (135-146 mmol/L)
Potassium         4.2               5.2          (3.5-5.1 mmol/L)
Urea                 4.4               11.3         (2.5-7.8 mmol/L)
Creatinine         69               139          (60–120 µmol/L)
Albumin            44                39           (35-50 g/L) 

Urine Dipstick

Blood 3+
Protein 1+
Leucocytes negative
Nitrites negative

Which of the following is the most likely diagnosis?