A 17-year-old patient is referred by his GP after presenting with periorbital oedema. The patient noticed the oedematous eyes 3 days ago, but repos feeling unwell since a throat infection 3 weeks ago with nausea and vomiting in the last week. A urine dipstick is positive for protein and blood while serum creatinine and urea are mildly deranged. The most likely diagnosis is: