SUFU 2018: Nerve Stimulation Increases Voiding Efficiency in a Novel Model of Detrusor Underactivity

Austin, TX ( Detrusor underactivity (DUA) is an understudied health concern that affects up to 45% of men and women. The limited availability of animal models that exhibit the integrated pathophysiology of DUA impedes the development of new therapeutic approaches. Dr. Eric Gonzalez and colleagues mentioned that the current studies characterized the bladder function of an obesity model of DUA and investigated neuromodulation as a management option to restore efficient bladder emptying. 

The authors had 8-week old female obese-prone (OP) and obese-resistant (OR) rats were purchased from Charles River (Boston, MA). OP and OR rats were fed a 45% fat diet from 9-21 weeks and a 60% fat diet from 21-24 weeks. Serum was collected from the tail vein for metabolic analysis at 8 and 24 weeks. Chronic bladder function (voided volume and voiding frequency) of OP rats was assessed twice per week from 8-24 weeks in a metabolism cage. At 24 weeks, OP and OR rats were anesthetized with urethane (1.2 g/kg s.c., supplemented as needed) and underwent acute single-trial cystometry. A paddle with platinum iridium contacts was placed on the EUS to record EMG signals and a bipolar microcuff was placed around the motor or sensory branch of the pudendal nerve or the pelvic nerve for electrical stimulation. Following diet-induced obesity (DIO), OP rats weighed more than OR rats and had normal blood glucose but developed hyperinsulinemia and hypertriglyceridemia. During the chronic monitoring of bladder function, the voiding frequency and voided volumes of OP rats remained relatively constant when normalized to water intake. OP rats, however, exhibited DUA and urinary retention following DIO in acute cystometry. Compared to OR rats, OP rats had increased volume threshold, decreased peak micturition pressure (p ≤ 0.001), decreased voiding efficiency (p ≤ 0.0001), and decreased EUS EMG activity during voiding. Patterned electrical stimulation of the motor branch of the pudendal nerve increased voiding efficiency two-fold in OP rats (p ≤ 0.05), whereas, stimulation of the sensory branch of the pudendal nerve did not alter voiding efficiency. OP rats also had no change in voiding efficiency and decreased evoked contraction amplitude with electrical stimulation of the pelvic nerve. 

The authors concluded that this animal model may be used to understand the pathophysiology of DUA and establish the efficacy of neuromodulation to recover efficient bladder emptying with urinary retention

Presented by: Eric Gonzalez, PhD 

Authors: Eric Gonzalez PhD and Warren Grill PhD, Department of Biomedical Engineering, Duke University, Durham, NC

Written by: Bilal Farhan, MD, Female Urology Fellow and Voiding Dysfunction, Department of Urology, University of California, Irvine at the Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction Winter Meeting (SUFU 2018), February 27-March 3, 2018, Austin, Texas