Three preterm infants presented with both severe or moderate arterial
hypertension and dehydration due to increased water and sodium urinary
excretion. In patient 1, water and sodium wasting were extremely seve
re and peaked at 575 ml/kg per day and 73 mEq/kg per day, respectively
. In all infants, urinary water and sodium excretion dramatically decr
eased when hypertension resolved. The overall clinical data suggest a
pressure natriuresis phenomenon.