Bladder neck mobility is a heritable trait.
OBJECTIVE
Congenital connective tissue dysfunction may partly be responsible for female pelvic organ prolapse and urinary incontinence. We undertook a heritability study to determine whether mobility of the bladder neck, one of the main determinants of stress urinary incontinence, is genetically influenced.


METHODS
Heritability study using a twin model and structural equation modelling.


METHODS
Queensland Institute of Medical Research, Brisbane, Australia.


METHODS
One hundred and seventy-eight nulliparous Caucasian female twins and their sisters (46 monozygotic pairs, 24 dizygotic pairs and 38 sisters) aged 18-24 years.


METHODS
We performed translabial ultrasound, supine and after bladder emptying, for pelvic organ mobility. Urethral rotation and bladder neck descent were calculated using the best of three effective Valsalva manoeuvres.


METHODS
Bladder and urethral mobility on Valsalva assessed by urethral rotation, vertical and oblique bladder neck descent.


RESULTS
Genetic modelling indicated that additive genes accounted for up to 59% of the variance for bladder neck descent. All remaining variance appeared due to environmental influences unique to the individual, including measurement error.


CONCLUSIONS
A significant genetic contribution to the phenotype of bladder neck mobility appears likely.
Dietz
H P
HP
University of Sydney, NSW 2751, Australia.
Hansell
N K
NK
Grace
M E
ME
Eldridge
A M
AM
Clarke
B
B
Martin
N G
NG
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000704:Analysis of Variance; D004777:Environment; D005260:Female; D040941:Heredity / Q000502:physiology*; D006801:Humans; D009068:Movement / Q000502:physiology*; D017773:Pelvic Floor; D010641:Phenotype; D011391:Prolapse; D014463:Ultrasonography; D014521:Urethra / Q000000981:diagnostic imaging / Q000502:physiology*; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000502:physiology*; D014549:Urinary Incontinence / Q000235:genetics; D014636:Valsalva Maneuver / Q000235:genetics