Some patients with ureteral stones suddenly experience a decrease in urine output, or oliguria, mostly due to poor drainage of urine produced by the kidneys as a result of stones becoming lodged behind the ureter. Stone impaction can be divided into incomplete obstruction and complete obstruction. If a patient with unilateral ureteral stones has a complete obstruction, he or she will not experience significant oliguria because the healthy kidneys will compensate by increasing the volume of urine, so the patient will not feel significant oliguria; if a patient with bilateral ureteral stones has a complete obstruction, he or she will gradually experience oliguria or even complete anuria because the urine produced by the kidneys is completely blocked by the stones and cannot be excreted; if a patient with bilateral ureteral stones has a complete obstruction, he or she will gradually experience oliguria or even complete anuria because the urine produced by the kidneys is completely blocked by the stones. Patients with incomplete obstruction of bilateral ureteral stones can still pass some urine through the gap between the ureter and the stones, but they may experience a decrease in urine output, and some patients who usually have a high urine output may suddenly experience back pain and urinate only 1-2 times a day. If this happens, patients are advised to go to the nearest hospital. If the urine is absent for a long period of time, the kidney function may be completely lost, so it is recommended that patients with ureteral stones and urine loss should seek medical attention.