The panels show the right and left kidneys of a patient. Note the dilated pelvis and calyces on the right compared to the left. Autopsy showed metastatic colonic carcinoma involving the right hilar and peri-ureteral soft tissues. The tumor in this area has caused outflow obstruction on the right, resulting in hydronephrosis and acute pyelonephritis. Bacterial, especially endogenous bacteria such as Escherichia coli, Proteus and Klebsiella.
Most cases are due to ascending infections from urine flow abnormalities.
Most cases are related to pre-existing urine outflow abnormalities such as tumor, pregnancy, calculi, prostatic hypertrophy, neurogenic bladder and vesicoureteral reflux. Women are more prone than men, possibly due to differences in urethral anatomy. Renal parenchymal involvement tends to be regional, not universal, commonly upper and lower poles. Cortical surfaces show suppurative abscesses. Since many cases are associated with urine outflow obstruction, dilatation of pelvis and calyces may be present.