# Intestinal invagination caused by circumferential contraction with longitudinal relaxation of the wall

## TL;DR

This study explores how uncoordinated muscle movements in the intestine can lead to intussusception, a condition where part of the intestine folds into itself.

## Contribution

A computational model is introduced to demonstrate how uncoordinated muscle contractions can cause intestinal invagination.

## Key findings

- Circumferential contraction with longitudinal relaxation of the intestinal wall leads to invagination.
- A square-shaped contracting region in the intestinal model also causes invagination.
- Uncoordinated muscle motion during peristalsis may increase the risk of pediatric intussusception.

## Abstract

Pediatric intussusception is frequently observed in the ileocecal region, where the terminal ileum invaginates into the colon. Previous studies have indicated an association between pediatric intussusception and inflammation as well as intestinal motility. However, the underlying mechanisms remain unclear, particularly with regard to the mechanics. We hypothesized that invagination occurs when longitudinal and circular smooth muscles are not coordinated during peristalsis. To test the hypothesis from a mechanical perspective, we developed a computational model of the terminal ileum, where the terminal ileum is modeled as a hyperelastic tube. We showed that circumferential contraction with longitudinal relaxation of the hyperelastic tube wall caused invagination in the contracting region of the tube. We also found that invagination occurred when a square-shaped contracting region emerged in the hyperelastic tube. These results indicate that uncoordinated motion of the circular and longitudinal muscles can lead to invagination of the intestinal wall. In addition, the configuration of peristalsis may serve as an indicator of the risk of pediatric intussusception.

The online version contains supplementary material available at 10.1007/s10237-025-02010-0.