The ultrastructure of acute pyelonephritis in the monkey.

P-fimbriated E. coli, which have specific receptors on urothelial cells for their fimbriae, were used to produce pyelonephritis. Using both scanning and electron microscopy, it was shown that the bacteria attached to ureteral epithelium by 12 hours after inoculation. They developed into a biolayer of bacteria covering the epithelium by 48 hours, but did not invade within that time. In the kidney, adherence was seen by 6 hours in collecting proximal and distal tubules. While many bacteria were seen, tubular epithelium remained normal through 24 hours. The inflammatory response was first seen at 48 hours. Phagocytosis was accompanied by mortal damage to both phagocytes and surrounding tubules. This was followed by bacterial invasion of the interstitium.