Rectal cancellation working well

The rectal pressure responds to any changes of the abdominal cavity due to straining or stress.
These can then be subtracted from the intravesical to give the true intrinsic bladder pressure from the detrusor muscle (detrusor pressure).
Quality control is important during cystometry. The cancellation from the rectal catheter must be accurate. The examples below shows several artefacts on t he rectal and vesical traces all of which are completely removed from the detrusor pressure by subtraction.

This is a stable bladder. All the artefacts in these traces derive from abdominal pressure. Unfortunately , the rectum "has a life of its own" and can generate its own pressures.
Click here to see 
rectal cancellation 
working badly
Click here to see 
rectal cancellation 
working well but with 
some rectal pressure 
contractions which 
can confuse

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