Is Dense persistent nephrogram seen in both hydronephrosis and pyelonephritis?
How do we distinguish between the two?
Dense persistent nephrogram is classically used in case of acute ureteric obstruction or hypotension.
Hydronephrosis usually shows rim nephrogram and pyelonephritis can show striated nephrogram.
These 2 can be differentiated by
clinical history (features like costo-vertebral tenderness and fever in pyelonephritis)
USG appearance (anechoic in hydronephrosis and hypoechoic with mobile echoes in pyelonephritis)
CECT (Hypodense in hydronephrosis and kinda rim enhancement like pattern in the latter).