Paediatricsmiddle twist
A 5-week-old boy has vomited after feeds for three weeks. The milk now comes back forcefully enough to reach the floor, and he immediately wants to feed again. He weighs 3.4 kg, below his birth weight of 3.6 kg, and has had no diarrhoea and no fever. Venous blood shows sodium 131 mmol/L (135-145), potassium 2.8 mmol/L (3.5-5.0), chloride 86 mmol/L (95-110), bicarbonate 36 mmol/L (22-32) and pH 7.52. Which one of the following best accounts for this biochemical picture?