Magnetic resonance imaging measurement of the anorectal striated muscle complex in normal children

Abstract

Purpose The aim of the study was to describe and establish a normal measurement of the striated muscle complex (SMC) in healthy children using body phased-array or head coil magnetic resonance imaging. Methods Imaging was performed in 20 boys and 20 girls (age range, from 3 months to 14 years; average age, 3.2 years) without anorectal disorders. The dimensions of the puborectalis muscle (PR) and external anal sphincter (EAS) were measured in different planes. Results There was a close positive correlation between absolute width and length of SMC and age ( P < .05), whereas there was no correlation between the relative width and length of SMC and age ( P > .05). Normal relative length of the PR and EAS were measured as 0.47 ± 0.04 and 0.41 ± 0.04, respectively, and the normal relative width of PR and posterior EAS were 0.50 ± 0.04 and 0.44 ± 0.04 in children younger than 14 years. Conclusions The width and length of PR and EAS increase progressively with age. The relative width and length of PR and EAS were not variable with age. A relative width and length of PR and EAS were chosen as objective criteria for normal SMC in children younger than 14 years.