Immunopathology of pyelonephritis: studies on the pathogenesis and diagnosis of the renal lesion.

Abstract

According to data from the Human Transplant Registry [1], chronic pyelonephritis (CPN) accounted for 14.1% of about 12000 patients requiring transplantation; it was second only to chronic glomerulonephritis as the cause of chronic renal failure. It is not certain how the diagnoses of CPN in this large series were made, but the figure is remarkably close to that we found with 100 consecutive bilateral nephrectomy specimens removed before transplantation at the Boston City Hospital and Boston University School of Medicine, in which complete gross and microscopic pathological examination was performed [2, 3]. The data from the transplant material are skewed towards a greater percentage of patients with chronic glomerulonephritis, since anatomic malformations often preclude transplantation for CPN. The term chronic pyelonephritis has come to signify a chronic renal disease caused by bacterial infection; however, the renal parenchymal lesions in this condition are largely nonspecific and can be produced by various types of injury. A number of studies [4] have emphasized that many patients with the pathologic lesions of CPN give no clinical evidence of infection, either recent of remote, and in our own series [2] about 50% of patients with clearcut CPN had no evidence of infection nor any of the conditions normally associated with CPN (i. e., obstruction or vesico-ureteral reflux). The terms abacterial CPN or nonbacterial CPN have thus emerged [5]. Heptinstall [6] cautions that the diagnosis of CPN should be restricted to cases in which there in inflammation and scarring of the pelvis or calyces. If this is done, the overall frequency of CPN diagnosed at autopsy and surgery diminished, but one is left with a number of cases of focal or diffuse chronic interstitial nephritis without pelvis scarring, in which no etiology is apparent. In addition, there is no a priori reason to attribute all cases with pelvis scarring to bacterial infection, since some patients with scarred pelves have no evidence of infection despite clinical progression [2, 5]. Other conditions such as vesico-ureteral reflux without infection [7] and analgesic nephropathy may result in calyceal deformities that are difficult to distinguish from those seen in chronic pyelonephritis.