Which condition results in the accumulation of urine in the renal pelvis due to obstruction?

Hydronephrosis is characterized by the accumulation of urine in the renal pelvis due to an obstruction in the urinary tract. This obstruction can occur at various points, such as the ureter, bladder, or urethra, and the resulting pressure buildup causes the renal pelvis and calyces to dilate. When urine cannot flow freely from the kidney, it leads to kidney swelling, which can eventually impair renal function if not addressed.

This condition is distinct from azotemia, which refers to the accumulation of nitrogenous waste products in the blood due to decreased kidney function, but does not specifically involve urine accumulation. Glomerulonephritis is an inflammatory condition affecting the glomeruli, often leading to proteinuria and hematuria, not the accumulation of urine. Hematuria involves the presence of blood in the urine, which may arise from various causes but does not pertain to urine backflow or accumulation in the renal pelvis.

Thus, hydronephrosis is accurately identified as the condition where urine accumulates in the renal pelvis due to an obstruction, highlighting its significance in renal pathophysiology.