Ultrasonic assessment of the urethra and the vagina in normal continent women and women suffering from stress in urinary incontinence and vaginal prolapse

Abstract

Urinary continence depends on two factors: the presence of an intact and strong internal urethral sphincter (IUS); and on an acquired behavior, gained by learning and training in early childhood, how to maintain a high alpha-sympathetic tone at the IUS keeping it closed all the time until there is a need. The IUS is a cylinder that extends from the urinary bladder neck to the urogenital diaphragm. It is composed of a strong collagen sheet with muscle fibers that intermingle with the collagen in the middle of the cylinder's thickness. The strong collagen sheet gives the IUS the high wall tension necessary to create the high urethral closure pressure. The muscle fibers, innervated by alpha-sympathetic nerves (T10-L2) are responsible for closure and opening of the urethra. Rupture of the IUS causes its weakness and it will not withstand increases of abdominal pressure, and urine will leak. Rupture and split of the collagen sheet are better demonstrated by imaging by 3D US and MRI. Normal vagina is a cylinder of collageno-elastic-muscular tissues. Its strong collagen sheet is responsible for keeping it in its normal upward and backward position. Labors cause redundancy and weakness of the vaginal walls with subsequent prolapse; and lacerations of the IUS which is intimately overlying the anterior vaginal wall. © Jaypee Brothers Medical Publishers (P) Ltd.