Experimental renal infection: acute and chronic studies of histology and function.

Experimental renal infections have resulted in histologic lesions of acute and chronic pyelonephritis, but in most studies the urinary tract has been "traumatized" to induce persistent infection. Sequential functional alterations have been measured infrequently. The present studies were designed to separate the functional and histological changes caused by high pressure sterile reflux from reflux with pathogenic organisms. Reproducible disruption of the pelvic epithelium with extravasation of solution into the parenchyma and vasculature occurred with reflux of 2.0 ml of solution but not with 1.0 ml. Reflux with 2.0 ml of sterile broth failed to cause permanent histologic changes, but reflux with broth containing organisms resulted in minor inflammatory changes. There was no decrease in renal function in either group. In long-term studies, no histologic changes in the cortex or medulla were noted 21 weeks after reflux of 1.0 ml of broth containing organisms; however, there was failure of functional maturation in the infected animals commensurate with their growth, as compared to the shams and controls (P = 0.03). Sterile reflux did not cause cortical scars or changes in renal function, but persistent parenchymal infection was associated with arrest of functional growth.