Dual segmental arterial supply to a single renal lobule: a study using semi-serial sections of mid-term fetuses

To determine which and how many segmental arteries supply a single renal lobule especially at and near the segmental border, as no data are available on the arterial supply to a single renal lobule (a pyramid and its covering cortex) at the border between renal segments.

We studied semi-serial sections (100 microm intervals; haematoxylin and eosin staining) of 26 kidneys obtained from 13 mid-term human fetuses (20-30 weeks gestation). Eleven fetuses were used for horizontal sections and two for sagittal sections. Section to section, we first traced the renal pyramids using a pen to understand the lobular configuration.

Fusion of the medullary pyramids was usually evident along the segmental borders, except for the border between the upper and middle segments. This fusion often accompanied a pair of arcuate arteries, each of which arose from a different renal segment, but shared a common corticomedullary junction to supply a single lobule. The incidence of fusion was high along the anterior border of the posterior segment as well as the border between the apical and upper segments. When the lower segmental artery entered the parenchyma distant from the renal hilus, fusion of pyramids occurred along the border between the posterior and lower segments in association with double arcuate arteries.

A single lobule is most likely to be shared by double segments at or near the segmental border. This morphology seems to be a result of lobule fusion during development and growth. Thus, in adults, a dual segmental supply to a single lobule seems to be more frequent than in fetuses.