Shafik Ahmed, Shafik Ali A, El-Sibai Olfat, Ahmed Ismail
Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, Cairo, Egypt.
World J Urol. 2003 Aug;21(3):167-70. doi: 10.1007/s00345-003-0340-5. Epub 2003 Jul 25.
Upon feeling the urge to urinate, the urinary bladder contracts, the urethral sphincters relax and urine flows through the urethra. These actions are mediated by the micturition reflex. We investigated the hypothesis that vesical contraction is maintained by positive feedback through continuous flow of urine through the urethra, and that the cessation of urine flow aborts detrusor contraction. Normal saline was infused into the urinary bladders of 17 healthy volunteers (age 35.2 years+/-4.2(SD); ten women and seven men) at a rate of 100 ml/min. On urge, which occurred at a mean volume of 408.6 ml+/-28.7 of saline, the subject micturated while the vesical and urethral pressures during voiding were being recorded; residual urine was measured. The test was repeated after anesthetizing the urethra with xylocaine gel or, on another occasion, after applying a bland gel. On micturition, the urine was evacuated as a continuous stream without straining; no residual fluid was collected. After urethral anesthetization, the fluid came out of the urethra in multiple intermittent spurts and only with excessive straining. There was a large amount of residual fluid (184.6 ml+/-28.4). The results of bland gel application showed no significant difference ( P>0.05) from those without gel. Detrusor contraction during micturition is suggested to be maintained by positive urethrovesical feedback elicited by the continued passage of urine through the urethra. This feedback seems to be effected through the urethrovesical reflex, which produces vesical contraction on stimulation of the urethral stretch receptors. Abortion of this reflex by urethral anesthetization resulted in failure of detrusor contraction and excessive straining was needed to achieve bladder evacuation in multiple spurts. The urethrovesical reflex is thus assumed to constitute a second micturition reflex responsible for the continuation of detrusor contraction and urination. The role of this reflex in the pathogenesis of micturition disorders needs to be studied.
当有排尿冲动时，膀胱收缩，尿道括约肌松弛，尿液经尿道排出。这些动作由排尿反射介导。我们研究了这样一个假设：膀胱收缩通过尿液持续流经尿道产生的正反馈得以维持，而尿液流动的停止会终止逼尿肌收缩。以100毫升/分钟的速率向17名健康志愿者（年龄35.2岁±4.2（标准差）；10名女性和7名男性）的膀胱内注入生理盐水。当平均注入量达到408.6毫升±28.7毫升生理盐水时出现排尿冲动，受试者排尿时记录膀胱和尿道压力；测量残余尿量。在用利多卡因凝胶麻醉尿道后或在另一次使用无刺激性凝胶后重复该测试。排尿时，尿液连续不断地排出而无需用力；未收集到残余液体。尿道麻醉后，液体以多次间歇性喷射的方式从尿道排出，且仅在过度用力时才排出。有大量残余液体（184.6毫升±28.4毫升）。使用无刺激性凝胶的结果与未使用凝胶的结果无显著差异（P>0.05）。排尿期间逼尿肌收缩似乎是由尿液持续流经尿道引发的正性尿道膀胱反馈维持的。这种反馈似乎是通过尿道膀胱反射实现的，该反射在刺激尿道牵张感受器时会引起膀胱收缩。尿道麻醉使该反射中断导致逼尿肌收缩失败，需要过度用力才能使膀胱以多次喷射的方式排空。因此，尿道膀胱反射被认为构成了第二个排尿反射，负责逼尿肌收缩和排尿的持续进行。该反射在排尿障碍发病机制中的作用有待研究。
