Answer: Dilation of the renal pelvis and calyces proximal to a blockage
The urinary tract obstruction is a blockage of the flow of urine out of the body. It is characterized by the dilation of the renal pelvis and calyces proximal to a blockage, which results to hydronephrosis and progressive fall in glomerular filtration rate (GFR).
Moreover, it is expected that the obstruction is due to a reduction in nephron glomerular filtration rate and a reduced number of filtering nephrons.