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Variation of rheological properties of the human rectal wall with distending volume
M Bouchoucha1, J P Jais, P Arhan
1Laboratoire de Physiologie digestive, Hôpital Laènnec, Paris, France.
Insights
This study analyzed rectal wall pressure-relaxation in children, finding the quasi-linear viscoelastic law applicable for mechanical property determination. Results show distinct initial relaxation curves and varying shapes across distension volumes.
Area of Science:
- Biomedical Engineering
- Gastroenterology
- Biomechanics
Background:
- Understanding the mechanical properties of the rectal wall is crucial for diagnosing and managing anorectal disorders.
- In vivo studies are needed to accurately model rectal wall behavior under physiological conditions.
Purpose of the Study:
- To define the conditions for applying the quasi-linear viscoelastic law to in vivo human rectal wall pressure-relaxation data.
- To evaluate the suitability of different normalization methods for rectal wall mechanical analysis.
Main Methods:
- Studied pressure-relaxation curves in 30 normal children across five distension volumes (10-50 ml).
- Compared three normalization methods: maximum pressure, first measured point, and passive state (inferior envelope).
- Utilized analysis of variance with repeated measures for statistical analysis.
Main Results:
- The initial relaxation curve (10 ml distension) significantly differed from others (p < 0.0001).
- The quasi-linear viscoelastic law is applicable for in vivo rectal wall mechanical property determination using mean measured points.
- Experimental curve shapes varied significantly with different distension levels (p < 0.0001).
Conclusions:
- The quasi-linearity hypothesis serves as an appropriate first approximation for modeling rectal wall rheological properties.
- Findings support the use of the quasi-linear viscoelastic model for in vivo rectal mechanics.
- The study highlights the importance of distension volume in rectal wall behavior analysis.
Abstract:
Pressure-relaxation curves of in vivo human rectal wall were studied in 30 normal children for 5 volumes of distension, 10-50 ml, to define the conditions of application of the quasi-linear viscoelastic law. Three normalization methods were compared: the use of the maximum pressure of the curve, the use of the first measured point after the rectal distension, and the use of the passive state defined as the inferior envelope of the experimental curve. Analysis of variance with repeated measures was used for data analysis. It was shown that: i) the first relaxation curve, corresponding to a 10-ml distension volume, was significantly different from the other curves (p < 0.0001); ii) the quasi-linear viscoelastic law could be applied to the in vivo determination of the mechanical properties of the rectal wall, when considering the mean level of the measured points; and iii) the shapes of the experimental curves at different level of distension were significantly different (p < 0.0001). We conclude that the hypothesis of quasi-linearity is appropriate, in a first approximation, as a model of rheological properties of the rectal wall.
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