Longitudinal and Radial Characteristics of Intra-Anal Pressures in Children Using 3D High-Definition Anorectal Manometry: New Observations

OBJECTIVES: The pathophysiology of fecal incontinence is not well understood. Standard or high-resolution anorectal manometry (ARM) provides simple two-dimensional (2D) intra-anal pressure measurements and do not identify radial asymmetry or localize abnormal sphincter function. 3D high-definition ARM (HDARM) has 256 pressure sensors distributed circumferentially and provides a detailed topographical and 3D pressure gradient representation of the anal canal. The objective of this study was to use HDARM to characterize intra-anal pressure profiles in children during rest and squeeze. METHODS: HDARM manometric tracings of 30 children with constipation referred for ARM were reviewed. 2D pressure profiles using high-resolution manometry were used to measure the length of the high-pressure zone (HPZ). The HPZ was divided into four equal segments from the anal verge to adjust for the variable sphincter length. Longitudinal and radial measurements of the HPZ during rest and squeeze (anterior, left, posterior, right quadrants of the HPZ) were taken along each segment in 2D and 3D topographical views. A 3D reconstruction combining all patients was then constructed. RESULTS: Mean age was 149.3±1.8 months and mean HPZ length was 3.0±0.1 cm. Using 2D manometry, the mean peak HPZ pressure at rest was 72.0±2.5 mm Hg, and was located in the second segment of the HPZ. The mean peak HPZ pressure at squeeze was 202.9±13.1, and was located in the second segment. 3D measurement demonstrated both longitudinal and radial asymmetry along the anterior, left, posterior, and right quadrants of the HPZ. Left and right quadrant pressures were higher than anterior and posterior pressures at the anal verge and segment 1 during rest and squeeze. Anterior pressures were lower than posterior pressures longitudinally and radially in segments 2, 3, and 4 both during rest and squeeze. Our findings also suggest that in pediatrics it may be necessary to adjust pressure measurement to the anal canal length to get a more accurate picture. CONCLUSIONS: 3D HDARM allows for a detailed characterization of intra-anal pressures. 3D topographic pressure measurements demonstrate longitudinal and radial asymmetry of the anal canal at rest and during squeeze. This is the first time longitudinal and radial asymmetry of the anal canal has been described in children. 3D HDARM may allow for a better understanding of the mechanisms of fecal continence in children.