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Rheology of human faeces and pathophysiology of defaecation

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Abstract

Background

Rectal evacuation involves multiple mechanisms that are not completely understood. The aim of this study was to quantify the rheologic property, i.e., yield stress, which governs the ease of deformation of a range of faeces of differing consistency and understand its influence on the pathophysiology of defaecation.

Methods

Yield stresses of faeces of differing consistencies and Bristol scores were determined by the Vane test. We then explored the effects of this property on ease of defecation using a simple static model of the recto-anal junction based on the laws of flow for yield stress pastes and checked the conclusions by X-ray defaecography experience.

Results

The yield stress of faeces increased exponentially with their solid content, from 20 to 8000 Pa. The static model of the recto-anal junction showed that evacuation of faeces of normal consistency and yield stress is possible with moderate dilatation of the anal canal, whilst the evacuation of faeces with higher yield stress requires greater dilatation of the anal canal. X-ray defaecography showed that such increases occurred in vivo.

Conclusions

The diameter of the recto-anal junction is increased to enable the passage of feces with high yield stress. The finite limits to such dilation likely contribute to fecal impaction. Hence, difficulties in defaecation may result either from unduly high yield stress or pathologies of reflex recto-anal dilatation or a combination of the two.

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Acknowledgements

The authors gratefully acknowledge Dr. François Laporte (Nutritional Biology and Oxidative Stress Unit, University Hospital, Grenoble) to have given them the authorization to perform the rheological measurements in his laboratory, and Prof. Bruno Bonaz (Gastroenterology Unit, University Hospital, Grenoble) to have given them the authorization to collect part of the material in his unit.

Funding

This work has been partially supported by the LabEx Tec 21 (Investissements d'Avenir—Grant agreement #ANR-11-LABX-0030). LRP is part of Institut Carnot PolyNat (Investissements d'Avenir—Grant agreement #ANR-11-CARN-030-01). RG Lentle thanks the Labex Tec21 for the funding of his stay at the Laboratoire Rhéologie et Procédés.

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Authors and Affiliations

  1. University Grenoble Alpes, CNRS, Grenoble, France

    C. de Loubens, A. Magnin & N. El Kissi

  2. Clinique du Mail, Grenoble, France

    A. Dubreuil

  3. MPRU, Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand

    R. G. Lentle

  4. Colorectal Unit, Department of Surgery, University Hospital, Michallon University Hospital, CS 10 217, 38043, Grenoble cedex, France

    J.-L. Faucheron

  5. University Grenoble Alpes, Grenoble, France

    J.-L. Faucheron

Authors
  1. C. de Loubens
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  2. A. Dubreuil
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  3. R. G. Lentle
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  4. A. Magnin
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  5. N. El Kissi
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  6. J.-L. Faucheron
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Correspondence to J.-L. Faucheron.

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de Loubens, C., Dubreuil, A., Lentle, R.G. et al. Rheology of human faeces and pathophysiology of defaecation. Tech Coloproctol 24, 323–329 (2020). https://doi.org/10.1007/s10151-020-02174-0

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  • DOI: https://doi.org/10.1007/s10151-020-02174-0

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