Chronic Pyelonephritis.

Typical coarse scars of chronic pyelonephritis associated with vesicoureteral reflux. The scars are usually polar and are associated with underlying blunted calyces.

Chronic Obstructive Pyelonephritis

Chronic Reflux-Associated Pyelonephritis (Reflux Nephropathy)

Morphological features

uneven scarring is useful in differentiating chronic pyelonephritis from the more symmetrically contracted kidneys associated with vascular sclerosis (often referred to as "benign nephrosclerosis") and chronic GN

scarring involving the pelvis or calyces, or both, leading to papillary blunting and marked calyceal deformities called caliectasis

Uneven interstitial fibrosis and an inflammatory infiltrate of lymphocytes, plasma cells, and occasionally neutrophils.Dilation or contraction of tubules, with atrophy of the lining epithelium

glassy-appearing PAS-positive casts known as colloid casts: thyroidization

glomerulosclerosis is seen in areas of better preserved renal parenchyma

tubular dysfunction occurs with loss of concentrating ability, manifested by polyuria and nocturia.

Chronic pyelonephritis. The surface (left) is irregularly scarred. The cut section (right) reveals characteristic dilation and blunting of calyces. The ureter is dilated and thickened, a finding that is consistent with chronic vesicoureteral reflux. B, Low-power view showing a corticomedullary renal scar with an underlying dilated deformed calyx. Note the thyroidization of tubules in the cortex