The anisotropic nature of urethral occlusive forces

A newly-developed unidirectional force gauge was used to demonstrate that the urethral occlusive forces are unequal around the circumference of the female urethra. In the proximal two-thirds of the urethra significantly greater forces are exerted in the anterior position compared with those exerted in the lateral and posterior positions. By contrast the occlusive forces in the distal third of the urethra are greater in the posterior and lateral positions than in the anterior position. These findings hold true for both women with normal and abnormal urinary control. Rotational variations have previously been reported but have been thought to be artefact due to catheter stiffness; this study shows that rotational variations are genuine and not due to artefact.