Kidney, Papilla - Necrosis

Renal papillary necrosis is a specific entity involving the tip of the renal papilla. Early stages involve loss of cellular definition and loss of staining affinity in the area of the papillary tip (Figure 1). More severe cases may involve necrosis of the entire renal papilla (Figure 2). Depending on the chronicity of the lesion, urothelial hyperplasia, hemorrhage, edema, inflammation, and mineralization may be evident. Often the necrotic papilla will slough off into the renal pelvis and result in obstruction (Figure 3). Re-epithelialization may be observed in sloughed areas. Inflammation is commonly observed adjacent to necrotic areas, and pyelonephritis may also be associated with papillary necrosis (Figure 4). Papillary necrosis is more commonly reported with chemical administration than from other causes. Spontaneous cases are uncommon in the rat and mouse.