What does "hydronephrosis" mean?

Hydronephrosis means swelling of the kidney due to urine backup, from hydro meaning water, nephr meaning kidney, and osis meaning abnormal condition. It occurs when urine cannot drain from the kidney to the bladder, causing pressure buildup that stretches and damages the renal pelvis and calyces. Common causes include kidney stones blocking the ureter, tumors compressing the urinary tract, urethral strictures, and benign prostatic hyperplasia in men. Bilateral hydronephrosis affects both kidneys and can rapidly lead to kidney failure. ---