What is the term for purulent material in the collecting system of the kidney due to obstruction?

The presence of purulent material in the collecting system of the kidney due to obstruction is referred to as pyonephrosis. This condition arises when there is an obstruction in the urinary tract, typically leading to infection and the accumulation of pus within the renal collecting system. Pus consists of dead white blood cells, bacteria, and cellular debris resulting from inflammatory processes, and its formation indicates a severe infection and inflammation of the kidney.

In contrast, hydronephrosis involves the dilation of the renal pelvis and calyces due to the accumulation of urine, which can occur when there’s an obstruction, but it is characterized by urine rather than pus. A renal abscess refers to a localized collection of pus within the kidney itself, whereas chronic pyelonephritis is a long-term inflammatory condition that results from recurrent kidney infections, but it does not specifically refer to the presence of purulent material due to acute obstruction like pyonephrosis does.