Hydronephrosis itself may not have any symptoms, but when hydronephrosis significantly increases, patients can feel soreness and discomfort in the lumbar region or upper abdomen. If the hydronephrosis is caused by urinary tract stones blocking the passage, patients often experience kidney pain and visible blood in the urine; if it is caused by congenital narrowing, it is prone to be complicated by urinary tract infections, with symptoms such as chills, fever, back pain, frequent urination, urgency, and painful urination. Sometimes, hydronephrosis occurs intermittently, with the patient experiencing abdominal pain, nausea, vomiting, and reduced urine output during an episode. The pain disappears after a few hours, followed by the excretion of a large amount of urine. This condition is often seen in ureteral obstruction. Of course, prolonged hydronephrosis can lead to renal failure, causing symptoms such as fatigue, poor spirit, anemia, and even swelling.