Electromyographic activity of the anterolateral abdominal wall muscles during the vesical filling and evacuation

The role of the anterolateral abdominal wall muscles (AAWMs) during the vesical filling and evacuation has not been sufficiently addressed in the literature. We have investigated the hypothesis that the AAWMs exhibit the increased electromyographic (EMG) activity on the vesical distension and contraction which presumably assists vesical evacuation. The effects of the vesical balloon distension on the vesical pressure (VP), vesical neck (VNP) pressures and the AAWMs'' EMG activity were studied in 28 healthy volunteers aged 40.7 ± 9.7 years (18 men, 10 women). These effects were tested after the individual anesthetization of the bladder and AAWMs and after saline infiltration. The VP and the VNP showed a gradual increase upon the incremental vesical balloon distension which started at a distending volume of 120–140 ml. At a mean volume of 364.6 ± 23.8 ml, the VP increased to a mean of 36.6 ± 3.2 cmH2O, the VNP decreased to 18.4 ± 2.4 cmH2O, and the AAWMs EMG registered a significant increase. This effect disappeared in the individual bladder and in the AAWMs'' anesthetization. However, it did not disappear in the saline administration. The AAWMs appear to contract simultaneously with vesical contraction. This action presumably increases the IAP and it assists vesical contraction. The AAWMs contraction on vesical contraction seems to be mediated through a reflex which is called the ''vesico-abdominal wall reflex''. Further studies are required to investigate the role of this reflex in vesical disorders.