MP49-08: Pre-Clinical Applications of High-Definition Manometry (HDM) System to Investigate Pelvic Floor Muscle Contribution to Urethral Closure Pressure in a Rabbit Model

Samuel Sorkhi*, Valmik Bhargava, Youngjin Seo, Kyoko Sakamoto, Mahadevan Rajasekaran, San Diego, CA

Introduction: Currently used single side-hole, sleeve sensors and microtip transducers often move and are unable to accurately record high pressure zones (HPZ) along the urethral canal during dynamic conditions. Current technology to determine leak point pressure (LPP; defined as the highest pressure recorded when a leak occurs; LPP ) in pre-clinical studies is cumbersome. High-definition manometry (HDM) has recently been introduced in the fields of urology and urogynecology to determine dynamic urethral closure pressure (UCP) changes in incontinent patients. However, the utility of this new tool in pre-clinical research is still not well explored. Our objectives are: 1) to evaluate the HDM probe utility in pre-clinical studies on UCP and LPP determinations; 2) to characterize the dynamic UCP profile at rest and during pharmacological (to stimulate internal smooth muscle sphincter) or electrical stimulation induced puborectalis muscle (an important pelvic muscle involved in UCP regulation) contractions.

Methods: A total of 6 female rabbits were anesthetized and prepared to measure UCP  using a HDM system that has 96 pressure sensors (Fig A). UCP was recorded at rest, and during electrical stimulation of the PRM. The effect of alpha-adrenergic agonist phenylephrine (PE; 100 µg/kg; IV) delivered via IV infusion was observed by measuring UCP after PE IV infusion.

Results: HDM pressure display is shown in Fig B – C.  After an IV injection, a modest increase (15-20 mmHg) in UCP (Fig D left) was noted. PRM stimulation (7 mA) significantly increased the UCP and demonstrated a striking increase (40-50 mmHg) (Fig D; right). Dotted white lines in Fig C - D identify the path of least resistance- defined as the lowest pressure in each circumferential ring of pressure sensors connected longitudinally from the bladder (BLD) to the vaginal end of the urethra. The maximum pressure (i.e., pressure that needs to be overcome for leakage to occur) on this path (Fig D) is identified by a red square.

Conclusions: Our data confirms that HDM is a viable system to measure dynamic pressure changes within the urethra, as well as to define the role of the PRM in the genesis of UCP in pre-clinical studies. LPP can be accurately determined using this system.

Source of Funding: VA Merit