Hypernatraemic dehydration: excess sodium is not the cause

I am grateful to Laing and Wong for raising once again the issue of hypernatraemic dehydration in the first few days of life.1 However, I think it is important to remember that hypernatraemic dehydration, like anaemia, is a sign of disease and not a diagnosis in itself. A low haemoglobin concentration in blood can be caused by a large number of different pathological and physiological processes. Hypernatraemic dehydration should be seen in the same light. Laing and Wong’s article describes two situations in which a child can be found to exhibit the typical biochemical and clinical features of hypernatraemic dehydration, that is—weight loss and hypernatraemia. The first mentioned is associated with gastroenteritis in a bottle fed infant, commonly a few weeks old and the second is seen in “breast fed” infants …