The patient has a certain amount of fluid in the bladder, and if residual urine in the bladder is detected by ultrasound, it will not cause a more serious disease if catheterization is carried out in time to remove the excess urine from the bladder. If the patient notices a bulging of the lower abdomen as well as a distended feeling, it is usually a more serious case of urinary retention, which can cause urinary fluid retention. If there is bilateral hydronephrosis, it can impair the function of both kidneys. Therefore, this is a serious condition and belongs to a kind of emergency in urology, which should be treated with cystostomy or catheterization in time. As for the causes of increased residual urine in the bladder and acute urinary retention, it is more common to have urinary obstruction, such as urethral stenosis, prostatic hyperplasia, urethral stones or abnormalities in bladder neurological function, such as neurogenic bladder, which can lead to weak bladder muscle contraction, and the above problems will occur, and the patient needs to be promptly treated to prevent complications caused by hydronephrosis.