RESUMEN
The present study deals with the problem of gestational age estimation through histological and morphometric approaches for the fetal kidney tissue. Thirty-five human fetuses that ranged from 12 to 38 weeks' of gestational age were investigated. Histological examination of the fetal kidney, including cortex and medulla, using H and E. Masson's Trichrome and P.A.S stains, allows us to define the principle modifications of the kidney during intrauterine life and to relate these to gestational age. The differentiation and maturation of the renal tubules preceded that of the glomeruli in the early developmental stages. Three distinctive developmental stages of renal glomeruli could be identified and classified: stage I, the most immature, stage II, moderately mature and stage III, the most mature, being the adult-like glomeruli. In spite of the appearance of the 3 developmental glomerular stages in the cortex of the same kidney at various periods of gestation [12-38 week], yet it was revealed that the key-element in both assessment of kidney maturation and gestational age estimation is the percentage of occurrence of mature glomeruli, stage III, as evidenced by area ratio of these glomeruli. In the medulla, a P.A.S. positive material was seen precipitated in both collecting tubules and Henle's loop, at 30 weeks gestation. Morphometric analysis for mature renal glomeruli i.e., stage III includes three parameters; mean number, mean total inner surface area and mean area ratio at various gestational periods [12-38 weeks], was carried out by means of Cell Image Analyzer System [CAS 200]. A direct proportional relationship has been found between advancement in gestational age and the mean area ratio of mature glomenuli at different gestational periods. This study validates routine histological techniques beside morphometric analysis of the human fetal kidney, being one of the products of conception, as a valuable tool for the forensic pathologist faced with the problem of gestational age assessment