Fig. 1.

Low-magnification light micrographs of zone 3 of pig 910 (A) and zone 4 of pig 921 (B) seen in transverse sections stained with picro-sirus red. Prominent reddish-stained bands are noted extending from the renal capsule as far down as the inner medulla (arrows), which define regions of interstitial fibrosis. Occasionally, these bands are associated with dimpling at the renal capsule (B, double arrows). In B, extensive scarring is noted to an entire renal lobule, which is outlined by a series of double arrowheads. A papillum from each section (outlined by a rectangle) is enlarged and seen as an inset at the bottom right of A and B. Bands of interstitial fibrosis are easily seen in the outer and inner medulla (arrows), which are interdispersed with dilated tubular profiles of inner medullary collecting ducts (single arrowheads).