Impedance pumping as a non-invasive treatment for underactive bladder? An ex-vivo proof-of-concept-study in porcine bladders.

In patients suffering from underactive bladder (UAB), the contraction of the detrusor muscle has insufficient strength or duration to ensure efficient bladder emptying. Although catheterisation is currently the most effective method to empty the bladder, it is also the biggest cause of urinary tract infections (due to the direct contact catheter-urine) in these patients. The present study aims at testing a new approach to empty the bladder, based on the impedance pump principle, which avoids contact with urine: a urine flow can be generated by applying an external intermittent compression on the urethra. To this end, isolated porcine bladders with urethras were placed on a holder and a linear motor was used as impedance pump by pinching the urethra at four distances from the bladder neck (4cm, 6cm and 8 cm) and four different compression frequencies (4Hz, 8 Hz, 12 Hz,16Hz). The activation of the impedance pump always generated a very steep increase in the flow. The pump performance (maximum and average flow rate) were found to depend on the pinching site and on the pinching frequency; optimal values were different for each bladder. The pressure inside the bladder remained, in all experiments, in a physiologically safe range of less than 10cmH2O. The present study represents a proof-of-concept showing that impedance pumping can be used to empty bladders. Based on this principle a portable, external and urine-contactless device can be developed to assist urination in UAB patients and it could represent a big improvement in their quality of life.