What is hydronephrosis: When the urinary tract is obstructed, the discharge of urine is blocked, resulting in increased intrarenal pressure, dilatation of the renal pelvis and renal calyces, and atrophy of the renal parenchyma, called hydronephrosis. The danger of hydronephrosis: if hydronephrosis is not lifted for a long time, it will lead to pus accumulation in the kidney (pus kidney), renal hypofunction and even renal failure (i.e. uremia). Symptoms of hydronephrosis: (1) Early or slow development can be asymptomatic. Those with heavy hydronephrosis may feel back pain, and in case of combined infection, they may have fever, back pain and pus urine. (2) There may be symptoms of the original disease causing hydronephrosis, such as renal colic and hematuria caused by stones. (3) Nausea, vomiting, lack of food and drink, generalized swelling, etc. may appear when the disease progresses to the uremic stage. Diseases causing hydronephrosis: (1) Stenosis at the junction of the renal pelvis and ureter. (2) Kidney stones and ureteral stones. (3) Renal pelvis tumor, ureteral tumor and bladder tumor growing at the ureteral opening. (4) Prostatic hyperplasia can cause bilateral hydronephrosis or even uremia. (5) Intra-abdominal tumors invade the ureter or compress the ureter, etc. Diagnosis of hydronephrosis: (1) According to symptoms and physical signs. (2) X-ray examination: cascade angiography or retrograde angiography. (3) Ultrasonography. (4) CT and MRI (magnetic resonance imaging). (5) Nuclear nephrography, etc. Treatment of hydronephrosis: Remove the obstructive etiology causing hydronephrosis.