The vast majority of kidney disease will be followed by urine lesions, so it is said that changes in urine are the window of kidney disease, which can respond to kidney lesions in a sensitive way. Therefore, the correct method of urine retention is necessary for the accuracy of the test and the judgment of kidney disease. The correct phrase for urine retention is: clean, fresh urine in the middle of the bladder for a long enough period of time. 1, how long to hold urine (urine retention time in the bladder): in general, urine should be retained in the bladder for 4-6 hours, such as urine held for too short a time, there are too few organic components in the urine, which can not accurately reflect kidney disease. 2, the time of urine retention: the first urine in the early morning is the best, because the morning urine has more formed fraction, which can accurately reflect the pathological changes in the kidneys. Some patients drink water in order to due to low urine, and then retain urine for a short period of time. This method makes the urine dilute and is not desirable. 3, vulva cleaning: women should clean their vulva before retaining urine to avoid contamination of urine by bacteria and epithelium in the urethra. Men should clean the foreskin of the penis to avoid mixing in bacteria. Also keep the middle urine, that is, if the urine stream is not in the middle, keep the middle urine. 4, fresh urine: do some time urine (i.e., random urine) when the examination, urine specimens from the collection to the examination of time can not exceed 1 hour, otherwise there are components of dissolution, bacterial contamination, affecting the results of the examination. Therefore, when patients do the corresponding examination, it is best to retain urine in the hospital, not at home and then brought to the hospital, the accuracy of the results of this urine is not enough . Several special cases of urine retention methods 1, female menstruation: menstruation does not retain urine. Retain urine 3 days after the completion of menstruation. 2, whether to keep urine fasting: in addition to the examination of urine sugar, urine bile original need fasting, other urine examination items do not need fasting, can eat. 3, urine bacterial culture of urine retention: in addition to the usual clean vulva, but also with a sterile container to retain urine. During the period of taking antibiotics, to stop antibiotics for 3 days before urine retention, otherwise it will affect the urine culture results. 4.The retention of urine for examination of urine osmosis: it is necessary to abstain from water for 8 hours starting the night before the examination, and then retain urine. 5, 24-hour urine retention method: urinate at 7:00 a.m. and discard, then collect each urine in a container, and the last urine at 7:00 a.m. the next day is also collected in the container. Measure and record the total amount of urine for 24 hours, then mix the urine and take 50-100 ml of urine for testing. 6. Preservation of urine specimens: In summer, due to the high temperature, a preservative is needed to preserve 24-hour urine. It is usually formaldehyde (0.2-0.5 ml of 40% formaldehyde per 100 ml of urine).