0.8mm kidney stones presenting with a small amount of fluid as well as dilatation of the upper part of the ureter are mainly seen in combination with concomitant ureteral stones, but also in ureteral stenosis, ureteral tumors, and other factors. Kidney stones may dislodge from their primary site and fall within the ureter. Because the diameter of the ureter is about 0.6 centimeters, small stones within the kidney can dislodge from the primary site into the ureter and become embedded there, causing dilatation of the ureter above the stone and hydronephrosis. Therefore, the presence of hydronephrosis and ureteral dilatation despite the presence of small stones in the renal pelvis is often considered due to the combination of stones in the middle and lower ureter. In addition, some patients may also have other factors such as ureteral stenosis and ureteral tumor at the same time, which can also lead to ureteral dilatation and hydronephrosis, so it is recommended to actively seek medical advice and follow the doctor’s instructions for examination and treatment.