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Related Experiment Videos

Relationship between intra-abdominal and intrarectal pressure in the proctometrogram

A MacDonald1, P J Paterson, J N Baxter

  • 1University Department of Surgery, Royal Infirmary, Glasgow, UK.

The British Journal of Surgery
|August 1, 1993
PubMed
Summary

During defecation, intrarectal pressure rises due to increased intrapelvic pressure, not rectal contraction or abdominal straining. True intrarectal pressure remains unchanged, indicating pelvic floor muscle activity is key.

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Area of Science:

  • Gastroenterology
  • Physiology
  • Pelvic Floor Function

Background:

  • Intrarectal pressure increases during defecation, but the contributing factors (abdominal straining, rectal contraction) are unclear without pelvic pressure measurement.
  • Accurate measurement of intrarectal pressure changes during defecation requires accounting for concurrent intra-abdominal or intrapelvic pressure variations.

Purpose of the Study:

  • To clarify the mechanisms behind intrarectal pressure increases during defecation.
  • To differentiate the roles of abdominal straining and rectal contraction in elevating intrarectal pressure.
  • To measure true intrarectal pressure changes by simultaneously assessing intrapelvic pressure.

Main Methods:

  • Anorectal manometry was employed in ten asymptomatic women.

Related Experiment Videos

  • A bladder catheter was used to measure intrapelvic pressure during rectal balloon filling and evacuation.
  • Intrarectal pressure was measured concurrently with intrapelvic pressure.

    • Main Results:

    • Rectal filling increased intrarectal pressure from 2 to 18 cmH2O, while intravesical pressure remained stable at 2 cmH2O.
    • Rectal evacuation increased intrarectal pressure to 68 cmH2O and intravesical pressure to 51 cmH2O.
    • The calculated true intrarectal pressure (intrarectal minus intravesical) did not increase during defecation.

    Conclusions:

    • The observed rise in intrarectal pressure during defecation is solely attributable to increased intrapelvic pressure.
    • Abdominal straining and rectal contraction do not independently elevate true intrarectal pressure during normal defecation.
    • Pelvic floor muscle activity significantly influences intrarectal pressure dynamics during defecation.