ABSTRACT
Although many experiments of renal infection in animals have been studied, its pathway, regional pathogenesis and the healing process are yet to be cleared exactly. Especially in human. we have infrequent opportunities to study the pathologic changes of the acute pyelonephritis by renal biopsy, because ot accompanying general symptoms such as fever and bacteremia. This study underwent to define these changes exactly. A strain of Escherichia coli No.018 :K77 was inoculated to rabbit bladder to produce retrograde pyelonephritis. The histopalho1ogical changes at the early stage of acute pyelonephritis, the pathways of bacterial invasion, distribution in the infected kidneys and healing process were studied by using light and electron microscope. The histopathological changes were characterized by degeneration and destruction of renal pelvis and tubular epithelial cells, and a massive infiltration of polymorphonuclear leukocytes. The inflammatory changes were initially found at renal fornix and progressed to medullar after 7 hours of bacterial inoculation. These changes extended to basement membrane accompanying with discrete chronic inflammatory changes after 9 hours. The inflammatory changes extended to cortex with bacilli within blood vessels after 12 hours and sustained until the end of first week. The chronic inflammatory. changes subsided as a whole of renal parenchyma until eighth weeks. Therefore we concluded that the retrograde pyelonephritis in rabbit extends rapidly from forniceal mucosa to capsule through tubule, interstitium and blood vessels, and the natural healing process occurs diffusery for longer period.