Absence of normal-appearing proximal tubules in the fetal and neonatal kidney: prevalence and significance.

Rare fetuses and neonates with kidneys lacking normal-appearing proximal tubules have been described. In order to ascertain the prevalence of this histologic finding, and to study its associated clinicopathologic features, 500 consecutive perinatal autopsies (performed from 1981 to 1985) were reviewed. Kidneys lacking normal-appearing proximal tubules were found in six of 500 (1.2%) perinatal autopsies (one liveborn and five stillborn cases). The liveborn infant was one of a sibship with renal tubular dysgenesis. Four of the stillborn fetuses were derived from monochorionic twin gestations; the histologic abnormality was present in only one fetus from each twin pair. Three of the four twin pairs had pathologic features suggestive of twin-to-twin transfusion, with the renal abnormality present in the donor twin; renal hypoplasia existed in two instances. The fourth affected twin was a stillborn acardiac fetus with multiple congenital anomalies and unilateral renal agenesis. The fifth stillborn was a hydropic fetus with trisomy 21 and renal hypoplasia. In this series, lack of recognizable renal proximal tubules most often was not a manifestation of renal tubular dysgenesis. The histologic finding was associated with stillborn, renal hypoplasia, and congenital anomalies, and was strongly associated with monochorionic twinning (P = 0.001). In the stillborn cases in this series, we suggest that this finding may represent renal tubular degeneration resulting from renal hypoperfusion.