What ultrasound finding is typical of hydronephrosis?

• A. Renal enlargement with increased cortical echogenicity.
• B. Dilation of the renal pelvis and calyces with thinning of the renal cortex if chronic.
• C. Normal ultrasound.
• D. Decreased cortical thickness with no dilation.

Answer: (B)

Hydronephrosis is defined by dilation of the kidney’s collecting system due to obstruction or urine backflow. On ultrasound, the hallmark is dilation of the renal pelvis and calyces—the pelvicalyceal system enlarges and appears as fluid-filled spaces inside the kidney. If the problem has been long-standing, pressure from the blocked urine can cause thinning of the renal cortex, reflecting loss of functional parenchyma. This combination—dilated pelvis and calyces with potential cortical thinning in chronic cases—is what distinguishes hydronephrosis from a normal kidney or other patterns.

Other findings don’t fit hydronephrosis: renal enlargement with increased cortical echogenicity points to parenchymal disease rather than collecting-system dilation; a normal ultrasound obviously shows no collecting-system dilation; decreased cortical thickness without dilation suggests cortical atrophy without collecting-system dilation, not hydronephrosis.