Lower back and lower abdomen pain after extracorporeal lithotripsy can be caused by ureteral spasm and hydronephrosis. 1. Ureteral spasm: after extracorporeal lithotripsy, the stones need to be discharged through the ureter and other channels, and the movement of the stones may cause irritation to the mucous membrane of the ureter, resulting in ureteral spasm or blockage, which may lead to lower back and lower abdominal pain. 2. Hydronephrosis: When the stone moves in the kidney, it will easily lead to the blockage of the renal calyx, which will lead to the dilatation of the calyx and accumulation of water, and also lead to the obstruction of the renal pelvis and ureteral junction, which will lead to hydronephrosis, which will cause pain in the waist and the lower abdomen. When pain in the lower back and lower abdomen occurs after extracorporeal lithotripsy, it is necessary to consult a doctor in a timely manner and take appropriate treatment under the guidance of a specialized doctor, which will help to alleviate the uncomfortable symptoms as soon as possible.