EMPTY VS. FULL URETHRAL PRESSURE PROFILOMETRY IN FEMALE STRESS URINARY INCONTINENCE: AN OBSERVATIONAL STUDY
Urodynamic (URD) testing is a widely used assessment tool that provides detailed information about bladder and urethral function. It is commonly used in the evaluation of female stress urinary incontinence (SUI). Its ability to identify intrinsic sphincter deficiency (ISD) and other lower urinary tract disorders has made it an attractive diagnostic modality to theoretically individualize treatment and improve patient counseling. However, its utility has been the source of recent controversy. Recommendations on appropriate patient selection for urodynamic testing has resulted in a marked decline in its use. Nevertheless, further exploration of its clinical applicability should be performed to better understand its potential.
Pathogenesis of SUI is generally believed to result from urethral hypermobility (Q-tip test greater than 30o) and /or intrinsic sphincter compromise. ISD is defined on the basis of URD parameters: Valsalva leak point pressure (vLPP) ≤ 60cm H2O pressure, and /or maximum urethral closure pressure (MUCP) ≤ 20 cm H2O pressure. Although the clinical implications of these measurements on treatment outcome has been well described, little is known about the dynamic properties of the urethra in the empty bladder state versus the full bladder state in a neurologically intact individual, nor the role of patient characteristics on such properties.
To describe the changes seen in maximum urethral closure pressure (MUCP) and functional urethral length (FUL) in the empty versus full bladder states in women with URD-proven SUI due to hypermobility and/or ISD.
Material & Methods
This was an IRB-approved, retrospective chart review study. All patients with URD- confirmed SUI or stress-predominant mixed urinary incontinence were identified over a 6 year period (7/2008-4/2014).
All URD studies were performed by a single physician adhering to guidelines set forth by the International Continence Society. ISD was defined by the following urodynamic criteria: Valsalva leak point pressure (vLPP) ≤ 60cm H2O pressure, and /or a maximum urethral closure pressure (MUCP) ≤20 cm H2O pressure.
The following patient information was collected: age, parity, mode of delivery, body mass index (BMI), tobacco exposure, menopausal status, medical co-morbidities, prior hysterectomy/bladder surgery, stages of prolapse, and post-void cough stress test results. Urethral pressure profilometry was performed following bladder catheterization (bladder “empty” state) and again at capacity (bladder “full” state). The URD parameters recorded included: MUCP-empty, MUCP-full, FUL-empty, and FUL-full.
Subjects were classified into 4 groups: Group A, SUI with urethral hypermobility; Group B, SUI without urethral hypermobility; Group C, ISD with urethral hypermobility; Group D, ISD without hypermobility. One way ANOVA and unpaired t-test was used to analyze data between groups, and significance was defined as p-value <0.05.
A total of 482 UDS were conducted, with 339 diagnosed with SUI or stress-predominant mixed incontinence on URD. Demographic data is shown in Table1. Groups A and C comprised the majority of subjects (175, 7, 153, and 4 patients were classified into Groups A-D, respectively).
There were differences seen in patient age (51.63 vs. 58.29 vs. 54.83 vs. 63, p <0.05), parity (3.22 vs.3.71 vs.3.11 vs.2.50, p<0.005), and BMI (30.47 vs.29.91 vs. 29.91 vs.34.77, p<0.005) between Groups A-D, respectively. Subjects who lacked urethral hypermobility (Groups B and D) as compared with those who did not (Groups A and C) were observed to have higher rates of menopause (86% &100% vs.49% & 63%), obesity (86% & 75% vs. 49% & 46%), and post-hysterectomy (29% &25% vs.15% &18%), whereas those with urethral hypermobility (Groups A and C) had slightly higher rates of pelvic organ prolapse (POP), (stage =/> 2).
Statistically significant differences were noted between the 4 groups in MUCP-empty (93.47 vs.87.71 vs.75.79 vs.54.25 cmH2O, p<0.001), MUCP-full (91.11 vs.74.29 vs.67.92 vs.44 cmH2O, p<0.001), and FUL-full (3.49 vs.3.73 vs.3.17 vs.2.40 cm, p <0.01), where subjects with ISD (Groups C and D) had significantly lower values. However, no significant difference was seen in MUCP or FUL between empty vs full bladder states across groups (Table 2).
Female subjects with SUI due to ISD had lower MUCP and FUL values than those with SUI due pto urethral hypermobility. Cystometric bladder volumes did not affect urethral pressure profilometry values in SUI. However age, parity, and BMI were found to differ between groups. Lack of urethral hypermobility (Groups B and D) was associated with a greater likelihood of postmenopausal state, obesity, and status osthysterectomy. The clinical implications of these findings need to be investigated further.