Chronic pyelonephritis, medulla, H/E, photomicrograph
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In chronic pyelonephritis, lymphocytes and plasma cells are the predominant inflammatory cells. They are in the interstitial space, between tubules, whereas in acute pyelonephritis the acute inflammatory cells are within tubules. The chronic inflammatory reaction has lead to fibrosis of the tubules, and contraction of the kidney. The remnant of a tubule is in the lower left hand corner (arrow).