FIGURE 13.

A, This example of simple and cortical hypoplasia is from a 3-week-old. The kidney weighed 8 g. The opposite kidney weighed 34 g. The histology of both cortex and medulla is normal. However, only 5 to 6 nephron generations are present. B, Although no cysts or dysplastic developmental abnormalities were noted in the above case a single focus of cartilage was noted among otherwise normal nephrons. C, Immunoperoxidase staining for epithelial membrane antigen on the case in Figures 11A and B shows poorly developed medullary rays in the center with only a few distal tubules and collecting ducts. D, This is a case of mixed simple and cortical hypoplasia from a 7-year-old. The kidney weighed 15.6 g (normal for age: 65 to 85 g). The histology of the cortex is normal but only 2 nephron generations are present in this lobe. The underlying medullary tissue at the bottom of the photograph shows collecting ducts in a densely cellular stoma. A few loops of Henle were present but not readily seen in this image.