Pressure – Flow Study

What is a Pressure – Flow Study?

A Pressure-Flow Study (Voiding Cystometry) is actually the next stage of Filling Cystomanometry (Full Urodynamic Study). It is conducted simultaneously and starts when the bladder has been filled up with the special catheter that measures intravesical pressure.

How is a Pressure – Flow Study performed?

It is primarily performed in neurologic patients (mainly paraplegic – quadriplegic – MS patients). A Pressure-Flow Study will be ordered before prostatectomy in men below 50 y.o. when there is suspected neurologic disorder, in elderly men (above 80 y.o.), in very large residual urine volume (>0,5 lt) etc.

What preparation is needed for a Pressure – Flow Study?

The same applies here as in Filling Cystomanometry.

How is a Pressure – Flow Study performed?

When the bladder is filled up with sterile water, the physician will ask the patient to urinate into a special device to have the bladder fully emptied.

How are the results of a Pressure – Flow Study intepreted?

The Pressure-Flow Study is the only fully reliable test to diagnose urinary obstruction. Urinary obstruction is usually anatomic, with the typical cases of prostate hyperplasia and urethral stricture. However, patients with spinal injuries have functional urinary tract obstruction, due to bladder sphincter dyssynergia. When patients with spinal injuries make an effort to urinate, instead of relaxing completely during voiding, the urethral sphincter muscle dyssynergically contracts causing the flow to be interrupted and the bladder pressure to rise. Besides urinary obstruction, the Pressure-Flow Study may identify a hypoactive bladder, i.e. the bladder detrusor may  lose its capacity to ‘push’ to allow all urine pass. This may occur, for example, in patients with insulin-dependent Diabetes Mellitus, because their uncontrolled blood sugar may have impaired their detrusor nerves.