A quantitative study of normal nephrogenesis in the human fetus: its implication in the natural history of kidney changes due to low obstructive uropathies.

An evaluation of nephrogenesis according to fetal age was performed by quantifying the state of the nephrogenic blastema (NB) and the number of glomeruli (GN) on frontal renal sections in 99 control fetuses (gestational age ranging from 9 to 40 weeks) and in 17 aborted fetuses with low urinary tract obstruction (gestational age ranging from 14 to 36 weeks). In the control group, GN increases slowly from the 10th to the 18th week, then abruptly from the 18th to the 32nd week, reaching an upper limit with NB disappearance by the 32nd week. In the uropathy group, the renal changes show a wide range of severity clearly accounted for by the impairment of both NB and GN. The dysplastic effect of urinary backpressure is the more consistent pathogeny with the spectrum of observed renal changes. It is likely, from GN used as a time-dependent marker of renal development, that the most severe dysplasia is the result of early obstruction with abnormal disappearance of NB and subsequent arrest of nephrogenesis.