Renal hemodynamics and tubular function in normal human pregnancy

Abstract

The study of renal function in human pregnancy is beset by many problems, summarized with exemplary clarity by Chesley [1]. Technical problems occur even with the most meticulous methodology, and conclusions must often be drawn from indirect evidence. Nevertheless, there has accumulated an extensive literature (see Ref. 2), from which general trends may be discerned. A major problem that must be overcome in studying renal function is the wide variation in absolute values between individual subjects. In the nonpregnant state, this may be resolved to some extent by correcting data to a standard body surface area of 1.73m 2 (and thus, by implication, to a standard kidney size) [3]. In pregnancy, however, the surface area nomogram is no longer applicable [4], The only realistic way to investigate renal changes, therefore, is to use each subject as her own control, that is, to perform serial studies on the same subject during pregnancy and in the nonpregnant state. Such demanding work has only occasionally been performed, but if the principle is neglected, significant changes in function may be missed altogether and erroneous conclusions may be drawn. This paper attempts to describe the changes that occur during human pregnancy in renal hemodynamics and in certain aspects of tubular function, particularly the handling of uric acid and glucose.