Experimental pyelonephritis: a new method for inducing pyelonephritis in the rat.

Induction of renal infection with Escherichia coli has been a problem in the investigation of experimental pyelonephritis. A consistent and reproducible infection was induced in the rat by use of a micropipette that introduced bacteria directly into the kidney. The gross appearances and histopathologic changes were similar to those seen during the course of pyelonephritis in man and were confined to the sites of inoculation. Bacteria persisted for extended periods in the kidney, but in contrast to other reports, infection was not confined to the medullary region. This model appears to have advantages over other models available and permits the establishment of a pyelonephritic process in prescribed areas of renal parenchyma.