In clinical practice, ultrasound of the urinary system generally refers to ultrasound of the kidneys, ureters and bladder, and in men, also includes examination of the prostate. In general, ultrasound examinations of the kidneys can be done without holding urine, which sometimes may cause the illusion of hydronephrosis. Ureteral ultrasound generally requires holding a small amount of urine, which is especially beneficial for detecting lesions such as stones in the lower ureter. The bladder is a cystic organ that is empty in its normal state, so only by holding urine can lesions in the bladder be detected, and the requirement to hold urine is relatively large. The actual fact is that you can find a lot of people in the world who are not able to get a good deal on a lot of things.