Experience with measurement of bladder electrical activity

Recording the evoked canine detrusor electromyogram

With increasing interest in detrusor disorders and possible detrusor myopathies, a method for recording the detrusor electromyogram (detrusor-EMG) would probably greatly assist the diagnosis of various bladder dysfunctions. Therefore, we investigated the electromyographic activity of the detrusor during sacral root stimulation and during spontaneous bladder contractions in six anesthetized dogs. In all experiments, a high correlation of detrusor-EMG recordings with bladder contraction was observed. Analysis in the time domain and power spectrum analysis revealed the most clear correlation of detrusor-EMG with intravesical pressure rise in a frequency band above 3 Hz. The spike duration was 100 to 250 ms with an amplitude of 100 to 500 microV. Low-frequency activity below 1 Hz was mainly presumed to be artifacts due to fluid movement under the electrode. Our trials indicate that smooth muscle EMG recordings from the detrusor smooth musculature are possible. The exact physiological relevance of the signal in the sub-Hertz domain (<1 Hz) is still uncertain. The presented animal model allows the pathophysiologic investigation of various pathologies of bladder dysfunction and detrusor myopathies. Neurourol. Urodynam. 18:687-695, 1999.

Bladder electromyograms and function in monkeys after atropine

Voiding induced in conscious monkeys by infusion of sterile saline into the bladder via a chronically implanted bladder catheter was stable over many months. Artefact-free recordings of electrical activity were obtained from the bladder neck and dome of these animals during bladder filling and voiding. Characteristic voiding electromyograms were recorded from both sites but were seen first in the record from the neck. Small doses of methyl-atropine abolished both voiding and the electromyograms; evoked responses to sacral ventral root stimulation were similarly prevented. Therefore the bladders of both man and monkey are very sensitive to atropine, unlike the bladders of most other animals.

Vesicourethral electromyography: facts or artefacts

A vesicourethral electromyographic study was carried out on 21 cats of both sexes with extracellular electrodes along with monitoring of contraction and relaxation of various parts of the bladder and urethra. No consistent electromyographic pattern of slow and fast waves was observed in the bladder and urethra either in any empty bladder or during filling and voiding phases. Most of the recorded waves were traced to a defined source of artefact. Twenty-two experiments were done with glass microelectrodes recording intracellularly in bladder strips of various animals bathed in normal and modified Krebs solutions. No spike activity was recorded during periods of contractions, whether spontaneous or electrically stimulated. Both in vivo and in vitro experiments suggest that the mechanism of excitation-contraction coupling of the bladder remains unidentified. The clinical application of bladder electromyography (EMG) has to be interpreted cautiously.