July 19, 2017
The renal biopsy image shows features characteristic of acute pyelonephritis. There is a neutrophil-rich interstitial inflammatory infiltrate and evidence of acute tubular injury. Some tubular lumens are filled with neutrophils (arrow), and in some areas, neutrophils encircle the outer aspect of the tubules between the tubular basement membrane and the interstitium (arrowhead). In some cases, micro abscesses may even form (not shown). In most cases of ascending infection, large vessels and glomeruli are uninvolved. If arteritis or neutrophilic infiltrates involve glomeruli, the possibility of a hematogenous infectious source should be considered.