Urology & Urogynecology > Education and Reference

The CMG is performed to evaluate the STORAGE PHASE of the micturition cycle and provides information on::

• The COMPLIANCE & STABILITY of the detrusor muscle bladder
• The CAPACITY of the bladder
• The transmission of SENSATION through the neurosensory pathways
• The COMPETENCE of the outlet

The ICS terms used for CMG are:

Q	flow
pves	vesical or bladder pressure
pabd	abdominal pressure
pdet	detrusor muscle pressure/activity
IVol	computed (infused) volume
EMG	external sphincter electromyography

The CMG part of a urodynamic study is highlighted below:

Some types of supplies used for CMG are depicted below:

For pves -

For pabd -

For EMG, patch or wire electrodes are used to measure the external sphincter activity. Placement of these electrodes is depicted below:

Wire electrodes for females -
Wire electrodes for males -
Patch (surface) EMG electrodes for females and males -

CMG Pressures:

CMG Pressures with Video:

Bladder compliance describes the relationship between change in bladder volume and change in detrusor pressure.

Common methods of determining compliance:

1. Use two “rule of thumb”:

- Compliance is normal if there is <15cm H2O increase in detrusor pressure as bladder is filled to a normal functional capacity.

- Compliance is normal if there is <1cm H2O increase in detrusor pressure for each 30- 50cc of infused volume.

2. The ICS Standard: Compliance is calculated by dividing the volume change by the change in detrusor pressure, during that change in bladder volume. Expressed as mls /cm H2O.