Catheter as source of error in urodynamic study.

The effect of introducing a fine catheter on the urethral wall was studied by electromyography in rabbits. On introducing the catheter, increased electrical activity in the form of biphasic potentials was recorded from the external sphincter and bladder neck. This indicates active muscular contraction of these regions. The biphasic potentials persisted for about four minutes and then became less frequent and lower in voltage until they disappeared completely after fourteen minutes. We conclude that in urodynamic studies one must wait for at least fifteen minutes after catheter introduction before recording the results.