Renal Function in Infants

We know that the main function of kidneys is their ability to produce the glomerular filtrate and thereby concentrating the urine by way of absorption of water from the glomerular filtrate. The ability to concentrate urine is not well developed in infants. Indeed the ability to concentrate urine is partially developed after three months of life and fully developed renal function is acquired by the end of first year of life. The lack of concentrating urine is because the kidneys are not adapted to the action of antidiuretic hormone (ADH) of pituitary gland. The kidneys gradually start responding to the ADH and acquire full ability within one year. If the infants are not given sufficient fluids during the first five days of life they are sure to loose 10% of their body weight. Adults with well developed renal function are capable of conserving fluid by reabsorption. The lack of concentrating power in the kidneys of infants is probably due to imperfect development of loop of Henle. In infants the tubular function is lower than the glomerular filtration rate (GFR). The reabsorption of water in infants is 70% to 80% less than the adults. An infant, therefore, has a narrow margin of defense against the factors which decrease body fluids. The renalfunction in infants is helpless to regulate water balance when water is lost by any reason like fever, vomiting or diarrhea and leads to clinical implications. Infants need special care during fever, vomiting or diarrhea to offset any dehydration.