Ultrasound is more accurate when the bladder is full. Under normal circumstances, the bladder is shrunken inside and there are folds inside, if something grows in the folds when the bladder is not full, it will be wrapped firmly by the folds and the ultrasound will easily miss the diagnosis. Above the bladder is the intestine, there is gas in the intestine, ultrasound is most afraid of gas, if the bladder is not full, after the gas interference ultrasound will not hit in, so the bladder will not show all. Only when the bladder is holding the gas up, when the abdominal wall is probed can we see whether there is anything growing in the bladder or not, whether there are stones or foreign bodies, including thick walls and diverticula or not. If older patients have abnormal urethral function and cannot hold their urine, they require cystoscopy in the urology department. The advantage of cystoscopy is that you can see under direct vision whether there is something growing in the bladder or not. If it is a stone, the cystoscope can also remove the stone, and if it is a tumor, you can do an electrodesiccation under the cystoscope to solve the problem at once.