Urethral sphincter morphology and function with and without stress incontinence.
OBJECTIVE
Using magnetic resonance images we analyzed the relationship between urethral sphincter anatomy, urethral function and pelvic floor function.


METHODS
A total of 103 women with stress incontinence and 108 asymptomatic continent controls underwent urethral profilometry, urethral axis measurement with a cotton swab, vaginal closure force measurement with an instrumented speculum and magnetic resonance imaging. Striated urogenital sphincter length was determined and its thickness was measured in the proximal sphincter, where its circular shape enables estimation of striated urogenital sphincter area. A length-area index was calculated as a proxy for volume.


RESULTS
The striated urogenital sphincter in women with stress incontinence was 12.5% smaller than that in asymptomatic continent women (mean +/- SD length-area index 766.4 +/- 294.3 vs 876.2 +/- 407.3 mm(3), p = 0.04). The groups did not differ significantly in striated urogenital sphincter length (13.2 +/- 3.4 vs 13.7 +/- 3.9 mm, p = 0.40), thickness (2.83 +/- 0.8 vs 3.11 +/- 1.4 mm, p = 0.09) or area (59.1 +/- 18.4 vs 62.9 +/- 24.7 mm(2), p = 0.24). Striated urogenital sphincter length and area, and the length-area index were associated during voluntary pelvic muscle contraction with more urethral axis elevation and increased vaginal closure force augmentation.


CONCLUSIONS
A smaller striated urogenital sphincter is associated with stress incontinence and poorer pelvic floor muscle function.
Morgan
Daniel M
DM
University of Michigan, Ann Arbor, Michigan, USA. morgand@umich.edu
Umek
Wolfgang
W
Guire
Kenneth
K
Morgan
Helen K
HK
Garabrant
Alice
A
DeLancey
John O L
JO
D000328:Adult; D000367:Age Factors; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D017773:Pelvic Floor / Q000473:pathology / Q000503:physiopathology; D011379:Prognosis; D012016:Reference Values; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D014521:Urethra / Q000473:pathology* / Q000503:physiopathology*; D014550:Urinary Incontinence, Stress / Q000175:diagnosis* / Q000209:etiology; D014563:Urodynamics