CHAPTER 100: Renal Transplant Pathology

Normal renal cortex. The normal renal cortex comprised of closely spaced proximal and fewer distal tubules, with interspersed glomeruli. This hematoxylin and eosin (H&E) stain demonstrates the abundant pink granular cytoplasm of proximal tubules, whereas the few distal tubules are lined by flatter, relatively paler epithelial cells (just below glomerulus at 5 o’clock, and upper center). The tubules are back to back, without intervening fibrous tissue or inflammatory cell infiltrates. A normocellular glomerulus is shown.

Normal renal cortex. The Periodic Acid Schiff (PAS) is helpful in delineating tubular and glomerular basement membranes. The proximal tubules have a luminal brush border that stains weakly magenta with PAS. Distal tubules lack this brush border and have a smaller diameter; a long vertical distal tubule can be seen at far right. Again, the tubules are very closely spaced. The urinary pole of this normal glomerulus is also shown, where the Bowman’s space is contiguous with the proximal tubular lumen (12 o’clock). PAS staining is quite useful in demonstrating certain pathologic features such as hyaline changes and lymphocytes permeating in tubules, which will be illustrated later.

Normal renal cortex. Silver stains, such as the Jones silver stain shown here, also stain basement membranes and are especially useful in evaluating glomerular pathology. In this normal glomerulus, the urinary pole is seen (at 2 o’clock), as is the juxtaglomerular apparatus with the macula densa (at 6–7 o’clock). The macula densa is the specialized portion of the distal tubule that provides tubular glomerular feedback within individual nephrons.

Normal renal cortex. Trichrome stains are especially important in determining the extent of interstitial fibrosis in a renal allograft. Collagen is stained blue in this Masson’s trichrome, or may be stained green in other trichrome preparations. A normal kidney should have minimal fibrous tissue between tubules in the cortex, as is shown here. Adequacy criteria for the renal allograft biopsy include 2 cores of renal cortex (as rejection may be patchy), sampling at least 10 glomeruli, although more is generally preferred. C4d staining may be performed on sections of cortex and medulla; some pathologies involve the medulla first/preferentially (polyoma virus infection, acute interstitial nephritis), yet an adequate sample of cortex is essential for assessment of rejection.

Normal artery. Normal arteries are composed of 3 layers, the outmost adventitia, which is often imperceptible in small arteries, the medial smooth muscle layer and the innermost intimal layer. In medium and large arteries, the internal elastic lamina separates the media and intima. The normal intima should comprise of a single cell layer of flat endothelium with ...