Pathogenesis of pyelonephritis. Escherichia coli-induced renal ultrastructural changes.

Escherichia coli-induced renal ultrastructural changes were observed 4 hr after the intravenous injection of 2 times 10-minus 6 bacteria. The initial changes consisted of mitochondrial swelling followed by intracellular vacuolation, nuclear membrane dilation, and increased lysosomal phagocytic activity. Alterations in the appearance of proximal tubular lysosomes included a loss of osmiophilic staining properties. Many of the involved cells showed necrosis and can presumably act as a nidus for bacterial proliferation.