Diagnosing intrinsic sphincteric deficiency: comparing urethral closure pressure, urethral axis, and Valsalva leak point pressures.

OBJECTIVES: Our purpose was to compare three measures proposed to diagnose intrinsic sphincteric deficiency: maximum urethral closure pressure, Valsalva leak point pressure, and straining urethral axis.

STUDY DESIGN: A total of 159 women with pure genuine stress incontinence had the three measures determined in a standardized fashion. Critical cutoff values for the Valsalva leak point pressure (52 cm) and urethral axis (22 degrees) were established by examining relative frequency distribution curves, using closure pressure of 20 as the arbitrary benchmark value for the prevalence of intrinsic sphincteric deficiency. The distribution of cutoff values is described and differences among the measures with respect to risk factors for intrinsic sphincteric deficiency and incontinence severity were determined.

RESULTS: Half the subjects fell below at least one cutoff value, but only 10% fell below all three. Sixty-four percent of subjects with either low closure pressure or leak point pressure had low values for the other, whereas 21% had discordance between them. Only 53% of subjects with low closure pressure and 40% with low leak point pressure had an axis < or = 22 degrees. Conversely, a substantial portion (36%) of subjects with pure genuine stress incontinence without urethral hypermobility had neither low urethral or leak point pressures. All three cutoff-values were associated with risk factors for intrinsic sphincteric deficiency, but only low closure and leak point pressures had significant associations with the severity of incontinence.

CONCLUSIONS: Intrinsic sphincteric deficiency should be diagnosed by a composite of historic, urodynamic, anatomic, and clinical severity criteria. We would include a maximum urethral closure pressure < or = 20, a Valsalva leak point pressure < or = 50, and a stress urethral axis < or = 20 in this composite.