title: High-frequency micro-ultrasound: a novel method to assess external urethral sphincter function in rats following simulated birth injury.
abstract: OBJECTIVE
  We evaluated external urethral sphincter (EUS) function using high-frequency micro-ultrasound (US) in rats that were either uninjured (Control, C) or underwent vaginal distension (VD) as a substitute for vaginal birth injury induced stress urinary incontinence (SUI).
  
  
  METHODS
  Thirteen female nulliparous Sprague-Dawley rats of 12 weeks were divided into two groups, either C (n = 6) or VD (n = 7). Vaginal balloon distension was performed under pentobarbital anesthesia for 4 hours. Five days after the injury, all animals underwent US assessment of the urethra during high-rate bladder filling and urine leakage/voiding. Urinary leakage, the presence, absence, and pattern of EUS bursting during the voiding phase were registered, and pre-determined parameters of intercontraction interval (ICI), length of contraction (LOC), and rate of contraction (ROC) were registered.
  
  
  RESULTS
  Our ultrasound findings consistently showed the presence of rhythmic EUS bursting in all of the C rats (6/6), which were absent in all VD rats (0/7). The mean of ROC, ICI, and LOC in C group were 3.02 ± 0.12 contractions/sec, 471.43 ± 17.9 msec, and 103.41 ± 3.28 msec, respectively.
  
  
  CONCLUSIONS
  Pre-determined parameters of LOC, ICI, and ROC during US provide objective and measurable data on EUS function. US showed the total disappearance of EUS bursting in the VD group as compared to the C group. These results indicate that ultrasound testing may become a valuable non-invasive tool in future translational studies to investigate SUI/urethral function in rat models.
authors.affiliation: Laboratory of Experimental Urology, Department of Development and Regeneration, KU Leuven, Leuven, Belgium; Department of Urology, Airlangga University School of Medicine/Dr. Soetomo General Hospital, Surabaya, Indonesia.
authors.forename: Lukman
authors.initials: L
authors.lastname: Hakim
authors.forename: Masayuki
authors.initials: M
authors.lastname: Endo
authors.forename: Andrew
authors.initials: A
authors.lastname: Feola
authors.forename: Doddy M
authors.initials: DM
authors.lastname: Soebadi
authors.forename: Jan
authors.initials: J
authors.lastname: Deprest
authors.forename: Dirk
authors.initials: D
authors.lastname: De Ridder
authors.forename: Maarten
authors.initials: M
authors.lastname: Albersen
authors.forename: Frank
authors.initials: F
authors.lastname: Van der Aa
mesh_terms: D000818:Animals; D001720:Birth Injuries / Q000150:complications; D004195:Disease Models, Animal; D005260:Female; D051381:Rats; D017207:Rats, Sprague-Dawley; D014463:Ultrasonography; D014521:Urethra / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D014550:Urinary Incontinence, Stress / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*; D014621:Vagina / Q000293:injuries
keywords: external urethral sphincter; high-frequency ultrasound; stress urinary incontinence; vaginal distension