Effect of hypotonic mannitol and saline load on diluting capacity in man

Renal growth and function in patients nephrectomized in childhood

Eight patients nephrectomized in childhood were studied with regard to growth and function of the remaining kidney. The age of the patients ranged between 8 1/2 and 31 years and the follow-up period was from 1 to 20 years. In most of the patients, repeated renal size determinations were made on postoperative urograms. Normal values for kidney size in childhood are also presented. The structural hypertrophy continued for at least three years after nephrectomy and was most pronounced in patients nephrectomized before three years of age. When more than three years had passed after nephrectomy the remaining kidney was 35-65% larger than normal. Healthy young adults and children with a previous history of urinary tract infection served as controls for function studies. The balance between glomerular and tubular function was well preserved in nephrectomized patients. The renal surface area showed the same relation to GFR and to reabsorption of bicarbonate in nephrectomized patients as in controls. It is therefore concluded that the increase in kidney function following unilateral nephrectomy is, at least in early life, primarily due to structural enlargement.

Development of renal control of salt and fluid homeostasis during the first year of life

This study describes the development of renal control of salt and water homeostasis. Twenty-three infants aged 3 weeks to 13 months were studied with respect to glomerular filtration rate (GFR) using single injection technique, ability to excrete an oral salt load, ability to excrete water, and diluting capacity. GFR developed exponentially, salt excretion linearly, water excretion was unchanged and diluting capacity actually decreased. A hypothesis is presented for the theoretical basis of this functional development taking into account the interdependence of the functional parameters studied. This theory might well explain the high incidence of hypernatremic dehydration in infants.