The low compliance bladder

The "normal" detrusor can accept 300 - 600 ml without marked rise in detrusor presure. 
In this case there is a marked rise in pressure and the bladder is said to accommodate (pressure decays again) when filling is stopped. 

Compliance is defined as DV/DP. It is has an instantaneous value and is known to  depend on filling rate. 
One does not make statements of the form "the detrusor compliance was 10ml per cm water" In practice detrusor compliance is usually defined in words (low or high) rather than numbers. 

The meaning of low compliance is a subject of much debate in the urodynamics community. Many spinal injury bladders demonstrate low compliance. 
The example shown is NOT spinal injury. This patient had detrusor instability at ambulatory studies. This is quite a common correlation.


NB. The physiologically filled detrusor is always high compliance. The rise in pressure that causes lower compliances is a function of the viscoelastic nature of the detrusor under higher filling rates. i.e. stretch the muscle too fast and it cannot accommodate completely.

Ambulatory study for same patient.

This patient had an unstable bladder when ambulatory urodynamics were performed.
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