There is no set time for exactly how long it will take for a ureteral stone to become dangerous to the patient after it causes hydronephrosis. However, the longer the history of the disease, the greater the degree of damage to the patient. Ureteral stones are most often secondary to kidney stone lesions, which form as a result of a kidney stone detaching from the kidney or falling into the ureter after treatment. If the stone becomes embedded in the ureter, it can lead to the development of hydronephrosis lesions. Due to individual differences and the strong compensatory function of the kidneys, patients may not have too obvious clinical symptoms in the early stage of the lesion. As the lesion continues to develop, the condition of hydronephrosis worsens, and the kidney function is gradually impaired, the patient may develop symptoms such as lower back and abdominal pain, nausea and vomiting, hematuria, pressure pain in the kidney area, abdominal mass and so on. The time of appearance of clinical symptoms and the severity of the symptoms vary according to the patient’s condition. Therefore, after the occurrence of hydronephrosis, how long it will be dangerous to patients is not fixed. Regardless of when the diagnosis of hydrocele lesion is found, you should go to the urology department as early as possible. Taking into account the specific condition of the patient, conservative treatment or surgical treatment will be taken to reduce the impact of the lesion on the patient.