Figure 1.

a: Light microscopy. Periodic acid-Schiff. Donor twin at 20 weeks’ gestation. RTD characterized by the absence of identifiable proximal tubules, retraction of glomerular tufts, and abundance of cortical and medullary interstitial cells. b and c: Immunolabeling, anti-EMA antibody (28-week twin pair). b: Donor twin. Most tubules are EMA-positive, between densely packed glomeruli. c: Recipient twin. Normal labeling of distal and collecting ducts and absence of labeling of proximal tubules. Comparison between b and c shows the reduced thickness of the cortex in the donor twin, owing to the absence of identifiable proximal tubules. Micrographs b and c, taken at the same magnification, were from a 28-week twin pair. Original magnification, ×80. Scale bar, 100 μm.