Hydronephrosis is an enlargement of the renal pelvis and calyces accompanied by atrophy of the renal tissue due to obstruction of the urinary tract. Urinary tract obstruction can occur anywhere in the urinary tract and can be unilateral or bilateral. The degree of obstruction can be complete or incomplete and can cause hydronephrosis after a certain period of time. Any part of the urinary tract tube stenosis or obstruction as well as neuromuscular dysfunction, urine through the obstacle can occur, resulting in urinary obstruction, obstruction above the part of the pressure due to poor urine discharge gradually increased, the lumen expansion, ultimately leading to fluid retention in the kidneys, dilatation, thinning of the renal parenchyma, renal hypoplasia, and bilateral obstruction, the consequences of the emergence of uremia is very serious. Enlargement of the renal pelvis and calyces due to urinary tract obstruction is accompanied by atrophy of renal tissue. Urinary tract obstruction can occur in any part of the urinary tract and can be unilateral or bilateral. The degree of obstruction can be complete or incomplete and can cause hydronephrosis after a certain period of time. Narrowing or blockage of any part of the urinary tract, as well as normal neuromuscular dysfunction, can obstruct the passage of urine, resulting in urinary obstruction. The pressure in the area above the obstruction gradually increases due to the failure to discharge urine, and the lumen enlarges, ultimately leading to hydronephrosis. Relieve obstruction, clear the urinary tract and protect kidney function. Non-surgical treatment is suitable for obstruction that can be relieved by itself. Etiologic treatment is the most ideal treatment. Nephrostomy. Resection of the affected kidney is feasible if the contralateral kidney has normal function.