Oedema and nephrotic syndrome — structured clinical encounter

A four-year-old boy is referred to your general paediatric clinic with three days of morning puffiness around the eyes and ankle swelling by the evening. He had an upper respiratory tract infection the previous week. He is afebrile and well in himself. His blood pressure is 95/60 mmHg, he has periorbital and ankle oedema, and his abdomen is slightly distended with shifting dullness. A random urine dipstick shows 4+ protein. His first morning urine protein-to-creatinine ratio is 340 mg/mmol, his serum albumin is 17 g/L, his creatinine is 40 micromoles per litre, and his complement C3 is normal. There is no haematuria.