In obstructive uropathy with hydronephrosis, which imaging finding is expected?

• A. Cortical thinning without dilation
• B. Normal ultrasound
• C. Calcifications in the renal papillae
• D. Dilation of the renal pelvis and calyces with thinning of the cortex

Answer: (D)

Obstructive uropathy raises pressure in the kidney’s collecting system, so the hallmark imaging finding is dilation of the renal pelvis and calyces (hydronephrosis). Over time, persistent back pressure damages the kidney tissue, causing thinning of the renal cortex. So you’d expect to see a distended collecting system with a thinned cortex on imaging. In acute obstruction you may see dilation without cortical thinning yet; the cortical thinning indicates chronic obstruction and parenchymal loss. Other options don’t fit because they either miss the dilated collecting system, show normal imaging, or point to calcifications that aren’t the typical sign of obstructive hydronephrosis.