Abstract

The lactulose/L-rhamnose urinary excretion ratio during continued infusion of milks containing both sugars was used as an index of the permeability of the neonatal bowel to large and small molecules. Healthy infants of gestational age 31-36 weeks proved to have a period of enhanced permeability to lactulose during the first week of life, the lactulose/L-rhamnose excretion ratio being significantly higher on day 2 than on days 9 or 16 when a mature pattern of permeability could be seen. In infants traumatised by asphyxia or sepsis this change was much less pronounced. Healthy preterm infants of gestational age 26-29 weeks showed a 'mature' pattern of permeability at birth, followed by a temporary period of enhanced permeability after 3-4 weeks of life. It is proposed that enhanced permeability to larger molecules is a specific temporary condition of the neonatal bowel in man as in other mammals, but the immunological implications in man remain to be established.