Dyssynergic defecation is a frequent condition in children with functional constipation (FC) caused by sphincter apparatus relaxation abnormalities and intra-rectal pressure during feces. The study’s goal was to investigate the frequency and type of dyssynergic defecation in children with FC, as well as the pressure in the anal canal poles during simulated evacuation and the function of the puborectalis muscle during feces. In 131 children with FC, three-dimensional (3D) high-resolution anorectal manometry (3D HRAM) were conducted. Resting pressure readings in four measuring poles of the anal canal were evaluated during the manometric test. The research included 131 youngsters ranging in age from 5 to 17 years. Dyssynergic defecation was observed in 106 of the 131 children studied. There was a statistically significant difference between the ages of the children studied and their intrarectal pressures at the anal canal measurement locations. In all forms of dyssynergy, there was a correlation between residual pressure values in lateral anal canal measuring poles and intrarectal pressure. Because of puborectal muscle weakness, 3D HRAM indicated an increase in rectal pressure during simulated defecation in a sample of 53/131 youngsters.

The rise in sphincter pressure in the lateral and posterior poles in I and II dyssynergia, and in the lateral poles in other kinds of dyssynergia, may be due to puborectal muscle relaxation problems during defecation.

Reference: https://journals.lww.com/jpgn/Abstract/2020/10000/Dyssynergic_Defecation_and_Anal_Sphincter.13.aspx