Hydropnephrosis is described as which condition?

• A. Infection of the kidney tissue
• B. Swollen kidneys due to edema
• C. Swollen kidneys full of urine
• D. Kidneys with trapped stones

Answer: (C)

Hydropnephrosis means the kidney is distended because urine has backed up into it from an obstruction. The word parts point to fluid-filled kidney tissue—the urine collects in the renal pelvis and calyces, causing the kidneys to become swollen. This description, swollen kidneys filled with urine, best captures the condition.

This differs from an infection of the kidney tissue, which would be nephritis or pyelonephritis and isn’t defined by urine-filled dilation. It also isn’t simply edema of the kidney tissue, which would be swelling from fluid in the tissue rather than accumulation of urine inside the kidney’s drainage system. Stones can cause the blockage that leads to hydropnephrosis, but the defining feature is urine-backed distension, not the presence of stones themselves.