Ultrasonic Assessment of the Internal Urethral Sphincter in Stress Urinary Incontinence

Abstract

A new concept was described in 1996 explaining micturition and urinary continence. Continence depends on a strong, sound and intact internal sphincter, and on an acquired behaviour of keeping a high alpha sympathetic tone. Weakness of the internal sphincter causes Stress Urinary Incontinence (SUI). Weakness is mostly due to rupture and or split of the wall. Ultrasound (U/S) assessment of the internal sphincter is utilised to demonstrate the defect of the internal sphincter wall. Three dimensional U/S assessment of the internal sphincter is done in 2 groups of women. The first group consists of 20 continent women. The second group consists of 60 patients with SUI who had clinical, radiological and urodynamic evaluation. Continent women have a linear internal sphincter that extends from the bladder neck down for almost the entire length of the urethral length. The internal sphincter has a thick symmetrical wall with 3 different echoes. In SUI patients, there is irregularity in the wall with areas of echolucency denoting the defect and rupture. Three dimensional U/S assessment of the internal unethral sphincter is very sensitive and specific for the diagnosis of SUI.