[quote author=zolton link=topic=26267.msg250470#msg250470 date=1255754444]
. . . . A particular favorite of mine is to drain the bladder but then refill it using sterile saline. The subs I've done this to tell me it is crazily erotic. Since we all empty only up to 80% of our bladders when we pee, we always have 20% full. To be totally emptied then to be filled to nearly 100% - the contrast they say is great. . . . .
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That is not correct.
You should be able to almost completely empty your bladder. If you leave 20% of urine after urinating, you have urinary retention, and that is NOT NORMAL and requires medical attention.
Urinary retention and incomplete bladder emptying can be caused by an inadequately contractile bladder, urethral sphincter obstruction, or both.
Urinary retention and incomplete emptying can result from a number of causes. In some cases, the flow of urine is blocked, for example, in men with benign prostatic hyperplasia. This causes obstruction. Another form of impaired emptying is nonobstructive, that is, there is no problem with the urethra but the bladder muscle is less able to adequately contract. When the bladder cannot contract properly, some or all of the urine remains in the bladder. If left untreated, this condition can lead to urinary tract infection and damage to the kidneys.