The Anterolateral Abdominal Wall Muscles During Vesical Filling and Evacuation: Electromyographic Study

ObjectivesThe role of the anterolateral abdominal wall muscles (AAWM) during vesical filling and evacuation has not been sufficiently addressed in the literature. We investigated the hypothesis that the AAWM exhibit increased electromyographic (EMG) activity on vesical distension and contraction that presumably assists in vesical evacuation.MethodsThe effect of vesical balloon distension on vescial (VP) and vesical neck (VNP) pressures and on AAWM EMG activity was studied in 28 healthy volunteers of age 40.7 ± 9.7 years (18 men and 10 women). This effect was tested after anesthetization on individual vesical and AAWM and after saline infiltration.ResultsThe VP and VNP showed gradual increase on incremental vesical balloon distension starting at a distending volume of 120 to 140 mL. At a mean volume of 364.6 ± 23.8 mL, the VP increased to a mean of 36.6 ± 3.2 cm H2O, the VNP decreased to 18.4 ± 2.4 cm H2O, and AAWM EMG registered a significant increase. This effect disappeared with anesthetization on individual vesical or AAWM, but not with saline administration.ConclusionsAAWM appear to contract simultaneously with vesical contraction; this action presumably increases the intra-abdominal pressure and assists vesical contraction. The AAWM contraction on vesical contraction seems to be mediated through a reflex that we call the “vesico-abdominal wall reflex.” Further studies are required to investigate the role of this reflex in vesical disorders.