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Urodynamics

What is urodynamics?

The term urodynamics refers to the study of pressure and flow in the bladder and urethra. It helps to diagnose problems of the bladder by measuring the pressure within the bladder during filling and emptying.

When might you need a urodynamic study?

Urinary symptoms such as frequency, urgency, hesitancy, incontinence and poor flow can arise from a variety of different urological problems. The treatment options differ according to the diagnosis and so it is important to pinpoint the root cause of any symptoms so that patients receive the appropriate treatment.

The test itself:

Patients are asked to lie on a bed and a local anaesthetic gel containing lignocaine is gently inserted into the urethra. This gel also contains antiseptic. Once the anaesthetic has taken effect a small catheter is inserted into the bladder and connected to the urodynamics machine.

The urinary catheter has a dual function: it enables the bladder to be filled but additionally it records the pressure within the bladder during filling and emptying.

A second small rectal catheter is then inserted into the rectum. It is necessary to record the pressure here so that any rise in bladder pressure caused by coughing, talking or straining to pass urine, for example, can be subtracted away. In this way an accurate measurement of bladder function is obtained.

The test is carried out usually in the sitting position and once the catheter and lines are securely attached and connected to the urodynamics machine fluid is slowly pumped into the bladder via the urthral catheter. Usually about 300-500 mls of water are put into the bladder over a 10-20 minute period. You will be asked when you:

  • first feel an urge to pass urine
  • feel a normal desire to pass urine
  • feel a strong desire to pass urine
  • have a sensation of having to pass urine urgently

Patients are usually asked to cough at regular intervals to check that the lines are correctly positioned.

At the end of the test you will be left in private to pass urine into a container which records the rate of flow. Once you have passed urine the catheters will be removed and the result will be discussed with you. The whole process should take about one hour.