Urinary retention is a clinical manifestation of BPH, characterized by increased obstruction up to a certain level, inability to empty the bladder of all urine during urination, and the appearance of bladder residual urine. The BPH is a disease in which the prostate increases in size, disrupts the normal structure and causes a series of dysfunctions mainly due to different degrees of glandular and/or fibrous and muscular tissue hyperplasia caused by disorders of sex hormone metabolism in the elderly. The following diseases are also causes of increased residual bladder urine: 1. Hemolytic uremic syndrome Gasser (1955) first reported 5 cases of children with a combination of hemolytic anemia, acute renal insufficiency and thrombocytopenia. Later, this triad of syndrome was called haemolytic uraemic syndrome (HUS), which was also called microangiopathic hemolytic anemia. Typical HUS is a syndrome with abnormal red blood cell morphology, characterized by hemolytic anemia, thrombocytopenia, and acute renal failure. 2. Urethral stricture Urethral stricture is an abnormally narrow mechanical lumen in any part of the urethra, resulting in increased resistance in the urethra and resulting in impaired urination. It is mostly seen in men. Urethral strictures can be divided into 3 major categories according to the etiology: congenital urethral strictures, inflammatory urethral strictures, and traumatic urethral strictures. As the hyperplastic fibrous tissue replaces the normal urethral spongiosa and forms a scar, the urethra and its surrounding tissues contracture, thus causing urethral stricture. 3, benign prostatic hyperplasia Benign prostatic hyperplasia (BPH) is a disease that is mainly due to different degrees of glandular and/or fibrous, muscle tissue hyperplasia caused by disorders of sex hormone metabolism in the elderly, resulting in an increase in prostate volume, destruction of normal structure and causing a series of functional disorders. Benign prostatic hyperplasia is a common disease in middle-aged and older men, with about half of men over the age of 50 experiencing clinical symptoms. The enlarged prostate squeezes the urethra, causing a series of symptoms of urinary disturbance, such as urinary frequency and urgency, weak urine stream, and incomplete urination. These symptoms seriously affect the quality of life of patients, and untreated can lead to many serious complications (such as acute urinary retention, stones, renal insufficiency, etc.) and even endanger patients’ lives. 4.Prostate cancer Prostate cancer is one of the main causes of cancer death in men in Europe and America. The incidence of prostate cancer increases with age, half of the prostate gland examined above the age of 80 has cancer foci, but the actual clinical incidence is much lower than this number, there are obvious regional and racial differences in the incidence of prostate cancer, according to statistics, the Chinese have the lowest, Europeans have the highest, Africa and Israel are in between, China and Japan and other countries are low incidence areas of prostate cancer, but there is no selection of men above the age of 50 autopsy prostate segmental sections found the number of latent cancer foci and The number of latent cancer foci found in autopsy of men over 50 years of age is similar to that of Europe and the United States. In addition, there is a relationship between prostate cancer and the environment. The posterior urethral valve is the most common congenital lower urinary tract obstruction in male children and is often detected as a result of hydronephrosis. With the widespread use of prenatal ultrasound, the detection rate of neonatal hydronephrosis has gradually increased, and early detection of posterior urethral valve has become possible.