Kidney stones falling into the ureter may cause hydronephrosis. Small kidney stones falling into the ureter will not lead to hydronephrosis, but slightly larger stones falling into the ureter will block urine drainage from the renal pelvis, and urine will accumulate in the kidney, and the pressure in the kidney will increase after urine accumulation, with dilatation of the renal calyx and renal pelvis, atrophy of renal parenchyma, and reduced renal function, thus causing hydronephrosis. Acute obstruction of the upper urinary tract often presents with low back pain, nausea, vomiting, hematuria and fever. Chronic obstruction of the upper urinary tract develops more slowly, and the symptoms are not obvious or only have the discomfort of lumbar distension. When it develops into huge hydronephrosis, a painless mass can be unintentionally palpated in the abdomen. Hydronephrosis caused by renal stone obstruction of ureter can be treated by relieving the stone obstruction, and the prognosis is generally better, and the best treatment is to treat the stone as soon as possible after it is found to be obstructing the ureter.