- Email: [email protected]
Size of Urogenital Hiatus as a Potential Risk Factor for Emptying Disorders After Pelvic Prolapse Repair
Size of Urogenital Hiatus as a Potential Risk Factor for Emptying Disorders After Pelvic Prolapse Repair Mohamed A. Ghafar,* Ralph R. Chesson, Cruz Velasco, Paul Slocum and J. Christian Winters† From the Department of Obstetrics and Gynecology, University of Mississippi Medical Center (MAG), Jackson, Mississippi, and Departments of Obstetrics and Gynecology (MAG, RRC, PS) and Urology (JCW) and School of Public Health (CV), Louisiana State University Health Sciences Center, New Orleans, Louisiana
Purpose: We correlated urogenital hiatus size and levator ani contraction strength with early postoperative emptying disorders. We also determined whether postoperative emptying disorders could be predicted before anti-incontinence procedures and pelvic organ prolapse repair. Materials and Methods: We retrospectively reviewed the charts of 225 consecutive patients after surgery for pelvic organ prolapse and/or stress urinary incontinence. Urogenital hiatus size was evaluated using pelvic organ prolapse quantification. Levator contraction strength was determined by the Oxford 0 to 5 classification scale. Emptying disorders were defined as post-void residual urine volume greater than 100 ml 48 hours postoperatively and/or discharge home with a Foley catheter or on intermittent self-catheterization. Results: Median patient age, post-void residual urine volume and urogenital hiatus size were significantly related to levator contraction strength (each p ⬍0.05). Univariate logistic regression analysis revealed a significant association of urogenital hiatus size (p ⫽ 0.001), post-void residual urine volume (p ⫽ 0.005) and levator contraction strength (p ⫽ 0.001) with emptying disorder status. Multivariate logistic regression analysis showed that levator contraction strength (p ⫽ 0.001) and post-void residual urine (p ⫽ 0.01) were independent predictors of emptying disorders. Conclusions: A wide urogenital hiatus, decreased levator ani contraction strength, increasing age and increased post-void residual urine correlated with an increased chance of early postoperative emptying disorders. The most independent predictors of early emptying disorders were decreased levator contraction strength and increased post-void residual urine.
Abbreviations and Acronyms C-index ⫽ concordance index GH ⫽ urogenital hiatus size PB ⫽ perineal body POP ⫽ pelvic organ prolapse PVR ⫽ post-void residual urine SUI ⫽ stress urinary incontinence Accepted for publication February 8, 2013. Study received institutional review board approval. * Correspondence: 2500 North State St., Jackson, Mississippi 39216 (telephone: 601-984-5314; FAX: 601-568-5477; e-mail: [email protected]). † Financial interest and/or other relationship with Astellas, Ferring, Allergan and Pfizer.
Key Words: urinary bladder, urethra, prolapse, female genitalia, urination disorders PELVIC organ prolapse and SUI are significant health issues affecting 17 million American women.1,2 Detachment of the uterosacral and cardinal ligaments from the pubocervical or rectovaginal fascia (level I support), or the separation of pubocervical and rectovaginal fasciae (level II support) are proposed as a mechanism of
POP.3 Urethral support has a central role in the female continence mechanism as the anatomical basis of urethral support due to interaction of the levator ani muscle through its connection to the arcus tendineus fascia of the anterior vaginal wall.4,5 Bladder neck function also has a role in the continence mechanism since loss of
0022-5347/13/1902-0603/0 THE JOURNAL OF UROLOGY® © 2013 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
http://dx.doi.org/10.1016/j.juro.2013.02.020 Vol. 190, 603-607, August 2013 RESEARCH, INC. Printed in U.S.A.
AND
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UROGENITAL HIATUS AS RISK FACTOR FOR EMPTYING DISORDERS AFTER PROLAPSE REPAIR
the bladder neck closure mechanism may also result in incontinence despite normal urethral muscle support.6 Voiding dysfunction ranges from irritative symptoms to obstructive voiding symptoms. Complete urinary retention is one of the most common and feared complications after pelvic reconstructive surgery and anti-incontinence procedures.7 Various surgical approaches have been described to treat urinary retention caused by bladder neck obstruction after anti-incontinence surgery.8 If early voiding dysfunction can be accurately predicted, it would be useful for preoperative patient counseling. Previous studies showed that a wide urogenital hiatus and a weakened levator system are associated with POP and SUI recurrence and progression.9,10 Of women who have never delivered vaginally a support defect is less likely to develop in those with a narrow genital hiatus than in women with a genital hiatus of greater than 2 cm.11 This leads to the assumption that a larger genital hiatus may be a marker of levator ani muscle disruption or pelvic muscle atrophy.12 Thus, we investigated whether it may be possible to predict emptying disorders based on these parameters. We correlated GH and levator ani contraction strength with postoperative emptying disorders. We also examined multiple parameters, including preoperative PVR, patient age, prolapse stage, PB, total vaginal length, and type of prolapse repair, surgery and anesthesia, for their relationship with early postoperative emptying disorders.
MATERIALS AND METHODS We retrospectively reviewed the office charts and collected data on 225 consecutive patients treated with surgery for POP and/or SUI from January 2008 to June 2010. Institutional review board approval was obtained before initiating the study. Patients were included if they underwent surgery for POP and or SUI during the study period. Collected data included demographic features, medical and surgical history, urinary symptoms, urinalysis, urodynamics, operative and pathology reports, postoperative voiding function and all postoperative visit assessments. POP and GH were measured using POP quantification.13 Pelvic muscle tone and levator contraction strength were determined by the Oxford 0 to 5 classification scale.14,15 This ordinal scale has well established test-retest reproducibility regarding the pelvic floor with contraction strength assigned a value of 0 —no contraction, 1—flicker, 2—weak contraction, 3—moderate contraction, 4 — good contraction and 5—strong contraction. Operations for POP included total vaginal height, McCall culdoplasty, uterosacral suspension, abdominal sacrocolpopexy and vaginal mesh placement with sacrospinous ligament fixation. The sling was placed as described by Ulmsten and Petros.16 A catheter was left in patients who underwent a POP procedure, which was removed on
postoperative day 1. Emptying disorders were defined as PVR greater than 100 ml 48 hours after surgery and/or the patient being discharged home with a urethral catheter or after being taught clean intermittent self-catheterization. A subjective assessment of voiding function was made at discharge and confirmed at the postoperative appointment. However, women were not offered routine postoperative voiding cystometry unless indicated by symptomatology. Statistical analysis was done using SAS® 9.2. Descriptive statistics were obtained for each variable. We assessed the distribution of predictor values according to pelvic strength as groups, using the exact chi-square test for discrete predictors, eg anesthesia, and the WilcoxonMann-Whitney test for continuous predictors, eg age. Univariate logistic regression analysis was done to assess unadjusted associations with voiding dysfunction status. Multivariate logistic regression analysis was performed with all variables on univariate analysis considered in stepwise selection and age kept in the model. Model building was subjected to leave-1-out internal cross-validation to assess final model stability. All tests were performed at the 5% significance level.
RESULTS A total of 209 patients with data on voiding dysfunction were included in analysis. All patients had a minimum of 3 followup visits. Median followup was 10 months (range 3 to 36). Neither prolonged urinary retention nor urinary retention requiring surgical revision were common in our study. A total of 73 patients had an emptying disorder PVR of greater than 100 ml and 2 were in persistent urinary retention for more than 4 weeks. In the latter 2 women voiding pressure study revealed obstructed voiding and the sling was released. Of the 209 study patients 136 (65%) did not have and 73 (35%) had voiding dysfunction. The original Oxford score was 0 in 42 cases, 1 in 44, 2 in 58, 3 in 38, 4 in 17 and 5 in 1. To avoid small frequencies for logistic regression analysis, pelvic strength Oxford scores were grouped as 0 or 1— contraction absent and 2 to 5— contraction present. There was a significant association of pelvic strength with GH (p ⫽ 0.009), age (p ⫽ 0.001) and PVR (p ⫽ 0.002) (supplementary table 1, http://jurology.com/). Univariate logistic regression analysis revealed that patients with a GH of greater than 5 cm were 3 times more likely to have emptying disorders than those with a GH of less than 5 cm (p ⫽ 0.001). A 5 cm measurement was used to dichotomize GH since prior studies showed that GH greater than 5 cm had clinical significance to predict the risk of recurrent prolapse.9 Median PB size 3.5 cm was an arbitrary measurement. Using continuous covariates for GH and PB led to similar results on univariate and multivariate analyses. Patients with a strength score of 0 or 1, or absent levator contraction were
UROGENITAL HIATUS AS RISK FACTOR FOR EMPTYING DISORDERS AFTER PROLAPSE REPAIR
Table 1. Adjusted multiple logistic regression of predictors of voiding dysfunction at hospital discharge in 183 patients OR (95% CI) Age/10 yrs Levator strength: 2–4 0, 1 PVR (ml): 100 or Less Greater than 100
0.970 (0.68,1.37) 1.00 18.7
p Value* 0.86 0.001
(8.0,43.6) 0.011
1.00 3.99 (1.36,11.6)
* Hosmer-Lemeshow test p ⫽ 0.819 and C-index ⫽ 0.839.
more likely to have emptying disorders than those who could contract the levator ani muscle (score 2 to 5) (p ⫽ 0.001). Also, older patients were more likely to have voiding dysfunction (p ⫽ 0.003, supplementary table 2, http://jurology.com/). Notably, 46 patients (79.3%) with a score of 2 did not have voiding dysfunction but 12 (20.7%) had dysfunction. This was almost the opposite of patients with a score of 0, of whom 9 (21.4%) did not have and 33 (78.6%) had voiding dysfunction. The final multivariate logistic regression analysis model showed that pelvic strength and PVR were significant predictors of voiding dysfunction (p ⫽ 0.001 and 0.01, respectively, table 1). The final model including age, pelvic strength and PVR had improved predictive accuracy over the best predictive univariate model including age (C-index ⫽ 0.839 vs 0.807). All possible 2-predictor interactions, 1 at a time, were tried in the final model. No interaction was significant at the 5% level and the C-index was about the same or considerably lower. These results were derived after performing leave-1-out internal cross-validation of the stepwise model selection. In all instances pelvic strength and PVR were included. In 8 instances total vaginal length was entered in the model but immediately removed. Table 2 shows the OR distribution from cross-validation.
DISCUSSION The most common complication associated with pelvic reconstructive surgery and urethral sling operations is urinary retention.17 Postoperative urinary retention might be due to bladder emptying disorders and/or bladder outlet obstruction. In our study 2 patients were in persistent urinary retention due to bladder outlet obstruction, which completely resolved after sling release. Although most patients resume normal voiding after pelvic surgery, as many as 40% may experience some degree of postoperative voiding dysfunction.18,19 Therefore, the ability to predict the risk of postoperative voiding dysfunction would be helpful.
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The pudendal nerve provides somatic innervation of the levator ani muscle, and the urethral and external anal sphincters. Neuromuscular injury was proposed as an underlying cause of prolapse.20 Pelvic floor denervation is thought to result in decreased levator tone and widening of the genital hiatus.21 Snooks et al reported that pudendal nerve latency was increased after childbirth, indicating injury.22 Most latencies recovered 1 year after delivery. Our results suggest that a large genital hiatus may be a marker of levator ani muscle disruption or levator muscle atrophy and incomplete bladder emptying. It is unlikely that levator weakness is the only explanation for GH size. There is a potential impact of pregnancy, behavior and life style exposures, such as exercise and chronic straining. Also, there are instances of levator ani neuromuscular damage, fibrosis and weakness that would not cause widening of the genital hiatus. Levator contraction strength strongly correlated with recurrent prolapse and incontinence after pelvic surgery, in addition to antiincontinence procedures.9 A weakened levator ani may have a role in predicting voiding difficulty. The basis of this theory is the concept that neuromuscular injury might also result in voiding difficulty, prolapse and SUI. In addition, a wide urogenital hiatus and muscle weakness result in urinary retention due to poor coordination. Our study confirms this hypothesis by showing that voiding dysfunction was 17 times more likely in patients with an absent or weak contraction strength score of 0 or 1 than in those with a score of 2 to 5. Patients with a urogenital hiatus of more than 5 cm were 3 times more likely to have incomplete emptying. There was also a strong correlation between GH size and pelvic muscle weakness (supplementary table 1, http://jurology.com/). Pelvic floor muscle dysfunction affects women of all ages. Muscle dysfunction can present as chronic pelvic pain, dyspareunia or rectal pain. Pelvic muscle weakness seems to affect the patient ability to coordinate the urethrovesical reflex of normal voiding function with poor ability to contract and relax the striated urethral sphincter. Dysfunction in any pelvic floor muscle group can be described in terms of low or high tone. Low tone pelvic floor muscle Table 2. OR of predictors selected by cross-validation
Minimum Quartile 1 Median Mean Quartile 3 Max
Age OR
PVR OR
Levator Strength OR
0.9905 0.9967 0.9969 0.9969 0.9972 1.0050
3.3833 3.9552 3.9778 3.9983 4.0027 4.9741
17.9201 18.4860 18.5495 18.7443 18.7254 21.9531
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UROGENITAL HIATUS AS RISK FACTOR FOR EMPTYING DISORDERS AFTER PROLAPSE REPAIR
dysfunction occurs when the muscles are weak and unable to contract. This is commonly associated with POP and SUI. High tone pelvic floor muscle dysfunction occurs when the muscles are chronically tense and lose the ability to relax. This is commonly associated with chronic pelvic pain, irritable bowel disorder and painful bladder syndrome.23 We included in the study only patients with POP and SUI with a high prevalence of pelvic floor muscle weakness. There are numerous clinic scales to evaluate pelvic floor muscle dysfunction, of which the most commonly used is the modified Oxford scale.14,15 It has been reproducible among examiners and was recommended to assess pelvic muscle integrity.24 Aging and parity are associated with fibrosis, variations in fiber diameter and centralization of nuclei in the levator ani muscle.25 In our study age and preoperative PVR were associated with voiding dysfunction. However, multivariate analysis revealed that preoperative pelvic muscle strength and preoperative high PVR were the most independent predictors of postoperative voiding dysfunction in patients with POP. To our knowledge this study is the first to correlate pelvic floor muscle weakness, genital hiatus size and incomplete bladder emptying. As our understanding of female voiding mechanisms increases, combining all parameters may enhance the predictive value of detecting postoperative voiding dysfunction. Further research to identify the biological mechanisms responsible for this association and a prospective study with external validation are needed to confirm the strength and generalizability of the associations.
Strengths of this study include application of the Oxford scale and POP quantification. Each technique is easy to use and has good reproducibility. The sample size of 73 patients with incomplete bladder emptying was sufficient to provide relatively precise estimates. Patients with weak pelvic muscles, high PVR and a large genital hiatus should be counseled about the increased risk of incomplete bladder emptying and prolonged postoperative catheterization. This would allow those at high risk to be taught clean intermittent selfcatheterization. Limitations of the current study include its retrospective nature. An optimal definition of postoperative emptying disorders is lacking but increased PVR greater than 100 ml is considered abnormal by most physicians. We could not address whether pelvic floor weakness was due to levator ani neuromuscular disruption, fibrosis or atrophy. Digital magnetic resonance imaging or ultrasound may be done to assess the different components of the levator ani muscle and their individual structural integrity.
CONCLUSIONS Levator contraction strength (0 or 1) and PVR greater than 100 ml were the independent predictors most associated with early emptying disorders. Patients with absent or flicker levator contraction strength should be counseled that they are at high risk for short-term voiding dysfunction. However, most cases of postoperative emptying disorders are self-limited and do not require further surgical intervention.
REFERENCES 1. Olsen AL, Smith VJ, Bergstrom JO et al: Epidemiology of surgically managed pelvic organ prolapse and urinary incontinence. Obstet Gynecol 1997; 89: 501. 2. Subak LL, Waetjen LE, Van den Eeden S et al: Cost of pelvic organ prolapse surgery in the United States. Obstet Gynecol 2001; 98: 646.
7. Chaliha C and Stanton SL: Complications of surgery for genuine stress incontinence. Br J Obstet Gynecol 1999; 106: 1238.
12. Khunda A, Shek KL and Dietz HP: Can ballooning of the levator hiatus be determined clinically? Am J Obstet Gynecol 2012; 206: 246.e1.
8. McGuire EJ, Letson W and Wang S: Transvaginal urethrolysis after obstructive urethral suspension procedures. J Urol 1989; 142: 1037.
13. Bump RC, Mattiasson A, Bo K et al: The standardization of terminology of female pelvic organ prolapse and pelvic floor dysfunction. Am J Obstet Gynecol 1996; 175: 10.
3. Boyles SH, Weber AM and Meyn L: Procedures for pelvic organ prolapse in the United States, 1979 –1997. Am J Obstet Gynecol 2003; 188: 108.
9. Vakili B, Zheng YT, Loesch H et al: Levator contraction strength and genital hiatus as risk factors for recurrent pelvic organ prolapse. Am J Obstet Gynecol 2005; 192: 1592.
4. DeLancey JO: Correlative study of paraurethral anatomy. Obstet Gynecol 1986; 68: 91.
10. Medina CA, Candiotti K and Takacs P: Wide genital hiatus is a risk factor for recurrence following anterior vaginal repair. Int J Gynaecol Obstet 2008; 101: 184.
15. Brink CA, Sampselle CM, Wells TJ et al: A digital test for pelvic muscle strength in older women with urinary incontinence. Nurs Res 1989; 38: 196.
11. Pierce CB, Hallock JL, Blomquist JL et al: Longitudinal changes in pelvic organ support among parous women. Female Pelvic Med Reconstr Surg 2012; 18: 227.
16. Ulmsten U and Petros P: Intravaginal slingplasty (IVS): an ambulatory surgical procedure for treatment of female urinary incontinence. Scand J Urol Nephrol 1995; 29: 75.
5. DeLancey JO: Anatomy and physiology of urinary continence. Obstet Gynecol 1988; 72: 296. 6. Petros PE and Ulmsten U: Role of the pelvic floor in bladder neck opening and closure I: muscle forces. Int Urogynecol J Pelvic Floor Dysfunct 1997; 8: 74.
14. Mantle J: Physiotherapy for incontinence. In: Textbook of Female Urology and Urogynecology. Edited by L Cardozo and D Staskin. London: Isis Medical Media 2001; pp 352–353.
UROGENITAL HIATUS AS RISK FACTOR FOR EMPTYING DISORDERS AFTER PROLAPSE REPAIR
17. Beck RP, McCormick S and Nordstrom L: The fascia lata sling procedure for treating recurrent genuine stress incontinence of urine. Obstet Gynecol 1988; 72: 699. 18. Kleeman S, Goldwasser S and Vassallo B: Predicting postoperative voiding efficiency after operation for incontinence and prolapse. Am J Obstet Gynecol 2002; 187: 49. 19. Book NM, Novi B and Novi JM: Postoperative voiding dysfunction following posterior colporrhaphy. Female Pelvic Med Reconstr Surg 2012; 18: 32.
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20. Heit M, Benson JT, Russell B et al: Levator ani muscle in women with genitourinary prolapse: indirect assessment by muscle histopathology. Neurourol Urodyn 1996; 15: 17.
23. Shafik A and El-Sibai O: Effect of levator ani muscle contraction on urethrovesical and anorectal pressures and role of the muscle in urination and defecation. Urology 2001; 58: 193.
21. Beersiek F, Parks AG and Swash M: Pathogenesis of ano-rectal incontinence. A histometric study of the anal sphincter musculature. J Neurol Sci 1979; 42: 111.
24. Abrams P, Cardozo L, Fall M et al: The standardization of terminology of lower urinary tract function: report from the Standardisation Sub-committee of the International Continence Society. Neurourol Urodyn 2002; 21: 167.
22. Snooks SJ, Swash M, Mathers SE et al: Effect of vaginal delivery on the pelvic floor: a 5-year follow-up. Br J Surg 1990; 77: 1358.
25. Jundt K, Kiening M, Fischer P et al: Is the histomorphological concept of the female pelvic floor and its changes due to age and vaginal delivery correct? Neurourol Urodyn 2005; 24: 44.
Purpose: We correlated urogenital hiatus size and levator ani contraction strength with early postoperative emptying disorders. We also determined whether postoperative emptying disorders could be predicted before anti-incontinence procedures and pelvic organ prolapse repair. Materials and Methods: We retrospectively reviewed the charts of 225 consecutive patients after surgery for pelvic organ prolapse and/or stress urinary incontinence. Urogenital hiatus size was evaluated using pelvic organ prolapse quantification. Levator contraction strength was determined by the Oxford 0 to 5 classification scale. Emptying disorders were defined as post-void residual urine volume greater than 100 ml 48 hours postoperatively and/or discharge home with a Foley catheter or on intermittent self-catheterization. Results: Median patient age, post-void residual urine volume and urogenital hiatus size were significantly related to levator contraction strength (each p ⬍0.05). Univariate logistic regression analysis revealed a significant association of urogenital hiatus size (p ⫽ 0.001), post-void residual urine volume (p ⫽ 0.005) and levator contraction strength (p ⫽ 0.001) with emptying disorder status. Multivariate logistic regression analysis showed that levator contraction strength (p ⫽ 0.001) and post-void residual urine (p ⫽ 0.01) were independent predictors of emptying disorders. Conclusions: A wide urogenital hiatus, decreased levator ani contraction strength, increasing age and increased post-void residual urine correlated with an increased chance of early postoperative emptying disorders. The most independent predictors of early emptying disorders were decreased levator contraction strength and increased post-void residual urine.
Abbreviations and Acronyms C-index ⫽ concordance index GH ⫽ urogenital hiatus size PB ⫽ perineal body POP ⫽ pelvic organ prolapse PVR ⫽ post-void residual urine SUI ⫽ stress urinary incontinence Accepted for publication February 8, 2013. Study received institutional review board approval. * Correspondence: 2500 North State St., Jackson, Mississippi 39216 (telephone: 601-984-5314; FAX: 601-568-5477; e-mail: [email protected]). † Financial interest and/or other relationship with Astellas, Ferring, Allergan and Pfizer.
Key Words: urinary bladder, urethra, prolapse, female genitalia, urination disorders PELVIC organ prolapse and SUI are significant health issues affecting 17 million American women.1,2 Detachment of the uterosacral and cardinal ligaments from the pubocervical or rectovaginal fascia (level I support), or the separation of pubocervical and rectovaginal fasciae (level II support) are proposed as a mechanism of
POP.3 Urethral support has a central role in the female continence mechanism as the anatomical basis of urethral support due to interaction of the levator ani muscle through its connection to the arcus tendineus fascia of the anterior vaginal wall.4,5 Bladder neck function also has a role in the continence mechanism since loss of
0022-5347/13/1902-0603/0 THE JOURNAL OF UROLOGY® © 2013 by AMERICAN UROLOGICAL ASSOCIATION EDUCATION
http://dx.doi.org/10.1016/j.juro.2013.02.020 Vol. 190, 603-607, August 2013 RESEARCH, INC. Printed in U.S.A.
AND
www.jurology.com
603
604
UROGENITAL HIATUS AS RISK FACTOR FOR EMPTYING DISORDERS AFTER PROLAPSE REPAIR
the bladder neck closure mechanism may also result in incontinence despite normal urethral muscle support.6 Voiding dysfunction ranges from irritative symptoms to obstructive voiding symptoms. Complete urinary retention is one of the most common and feared complications after pelvic reconstructive surgery and anti-incontinence procedures.7 Various surgical approaches have been described to treat urinary retention caused by bladder neck obstruction after anti-incontinence surgery.8 If early voiding dysfunction can be accurately predicted, it would be useful for preoperative patient counseling. Previous studies showed that a wide urogenital hiatus and a weakened levator system are associated with POP and SUI recurrence and progression.9,10 Of women who have never delivered vaginally a support defect is less likely to develop in those with a narrow genital hiatus than in women with a genital hiatus of greater than 2 cm.11 This leads to the assumption that a larger genital hiatus may be a marker of levator ani muscle disruption or pelvic muscle atrophy.12 Thus, we investigated whether it may be possible to predict emptying disorders based on these parameters. We correlated GH and levator ani contraction strength with postoperative emptying disorders. We also examined multiple parameters, including preoperative PVR, patient age, prolapse stage, PB, total vaginal length, and type of prolapse repair, surgery and anesthesia, for their relationship with early postoperative emptying disorders.
MATERIALS AND METHODS We retrospectively reviewed the office charts and collected data on 225 consecutive patients treated with surgery for POP and/or SUI from January 2008 to June 2010. Institutional review board approval was obtained before initiating the study. Patients were included if they underwent surgery for POP and or SUI during the study period. Collected data included demographic features, medical and surgical history, urinary symptoms, urinalysis, urodynamics, operative and pathology reports, postoperative voiding function and all postoperative visit assessments. POP and GH were measured using POP quantification.13 Pelvic muscle tone and levator contraction strength were determined by the Oxford 0 to 5 classification scale.14,15 This ordinal scale has well established test-retest reproducibility regarding the pelvic floor with contraction strength assigned a value of 0 —no contraction, 1—flicker, 2—weak contraction, 3—moderate contraction, 4 — good contraction and 5—strong contraction. Operations for POP included total vaginal height, McCall culdoplasty, uterosacral suspension, abdominal sacrocolpopexy and vaginal mesh placement with sacrospinous ligament fixation. The sling was placed as described by Ulmsten and Petros.16 A catheter was left in patients who underwent a POP procedure, which was removed on
postoperative day 1. Emptying disorders were defined as PVR greater than 100 ml 48 hours after surgery and/or the patient being discharged home with a urethral catheter or after being taught clean intermittent self-catheterization. A subjective assessment of voiding function was made at discharge and confirmed at the postoperative appointment. However, women were not offered routine postoperative voiding cystometry unless indicated by symptomatology. Statistical analysis was done using SAS® 9.2. Descriptive statistics were obtained for each variable. We assessed the distribution of predictor values according to pelvic strength as groups, using the exact chi-square test for discrete predictors, eg anesthesia, and the WilcoxonMann-Whitney test for continuous predictors, eg age. Univariate logistic regression analysis was done to assess unadjusted associations with voiding dysfunction status. Multivariate logistic regression analysis was performed with all variables on univariate analysis considered in stepwise selection and age kept in the model. Model building was subjected to leave-1-out internal cross-validation to assess final model stability. All tests were performed at the 5% significance level.
RESULTS A total of 209 patients with data on voiding dysfunction were included in analysis. All patients had a minimum of 3 followup visits. Median followup was 10 months (range 3 to 36). Neither prolonged urinary retention nor urinary retention requiring surgical revision were common in our study. A total of 73 patients had an emptying disorder PVR of greater than 100 ml and 2 were in persistent urinary retention for more than 4 weeks. In the latter 2 women voiding pressure study revealed obstructed voiding and the sling was released. Of the 209 study patients 136 (65%) did not have and 73 (35%) had voiding dysfunction. The original Oxford score was 0 in 42 cases, 1 in 44, 2 in 58, 3 in 38, 4 in 17 and 5 in 1. To avoid small frequencies for logistic regression analysis, pelvic strength Oxford scores were grouped as 0 or 1— contraction absent and 2 to 5— contraction present. There was a significant association of pelvic strength with GH (p ⫽ 0.009), age (p ⫽ 0.001) and PVR (p ⫽ 0.002) (supplementary table 1, http://jurology.com/). Univariate logistic regression analysis revealed that patients with a GH of greater than 5 cm were 3 times more likely to have emptying disorders than those with a GH of less than 5 cm (p ⫽ 0.001). A 5 cm measurement was used to dichotomize GH since prior studies showed that GH greater than 5 cm had clinical significance to predict the risk of recurrent prolapse.9 Median PB size 3.5 cm was an arbitrary measurement. Using continuous covariates for GH and PB led to similar results on univariate and multivariate analyses. Patients with a strength score of 0 or 1, or absent levator contraction were
UROGENITAL HIATUS AS RISK FACTOR FOR EMPTYING DISORDERS AFTER PROLAPSE REPAIR
Table 1. Adjusted multiple logistic regression of predictors of voiding dysfunction at hospital discharge in 183 patients OR (95% CI) Age/10 yrs Levator strength: 2–4 0, 1 PVR (ml): 100 or Less Greater than 100
0.970 (0.68,1.37) 1.00 18.7
p Value* 0.86 0.001
(8.0,43.6) 0.011
1.00 3.99 (1.36,11.6)
* Hosmer-Lemeshow test p ⫽ 0.819 and C-index ⫽ 0.839.
more likely to have emptying disorders than those who could contract the levator ani muscle (score 2 to 5) (p ⫽ 0.001). Also, older patients were more likely to have voiding dysfunction (p ⫽ 0.003, supplementary table 2, http://jurology.com/). Notably, 46 patients (79.3%) with a score of 2 did not have voiding dysfunction but 12 (20.7%) had dysfunction. This was almost the opposite of patients with a score of 0, of whom 9 (21.4%) did not have and 33 (78.6%) had voiding dysfunction. The final multivariate logistic regression analysis model showed that pelvic strength and PVR were significant predictors of voiding dysfunction (p ⫽ 0.001 and 0.01, respectively, table 1). The final model including age, pelvic strength and PVR had improved predictive accuracy over the best predictive univariate model including age (C-index ⫽ 0.839 vs 0.807). All possible 2-predictor interactions, 1 at a time, were tried in the final model. No interaction was significant at the 5% level and the C-index was about the same or considerably lower. These results were derived after performing leave-1-out internal cross-validation of the stepwise model selection. In all instances pelvic strength and PVR were included. In 8 instances total vaginal length was entered in the model but immediately removed. Table 2 shows the OR distribution from cross-validation.
DISCUSSION The most common complication associated with pelvic reconstructive surgery and urethral sling operations is urinary retention.17 Postoperative urinary retention might be due to bladder emptying disorders and/or bladder outlet obstruction. In our study 2 patients were in persistent urinary retention due to bladder outlet obstruction, which completely resolved after sling release. Although most patients resume normal voiding after pelvic surgery, as many as 40% may experience some degree of postoperative voiding dysfunction.18,19 Therefore, the ability to predict the risk of postoperative voiding dysfunction would be helpful.
605
The pudendal nerve provides somatic innervation of the levator ani muscle, and the urethral and external anal sphincters. Neuromuscular injury was proposed as an underlying cause of prolapse.20 Pelvic floor denervation is thought to result in decreased levator tone and widening of the genital hiatus.21 Snooks et al reported that pudendal nerve latency was increased after childbirth, indicating injury.22 Most latencies recovered 1 year after delivery. Our results suggest that a large genital hiatus may be a marker of levator ani muscle disruption or levator muscle atrophy and incomplete bladder emptying. It is unlikely that levator weakness is the only explanation for GH size. There is a potential impact of pregnancy, behavior and life style exposures, such as exercise and chronic straining. Also, there are instances of levator ani neuromuscular damage, fibrosis and weakness that would not cause widening of the genital hiatus. Levator contraction strength strongly correlated with recurrent prolapse and incontinence after pelvic surgery, in addition to antiincontinence procedures.9 A weakened levator ani may have a role in predicting voiding difficulty. The basis of this theory is the concept that neuromuscular injury might also result in voiding difficulty, prolapse and SUI. In addition, a wide urogenital hiatus and muscle weakness result in urinary retention due to poor coordination. Our study confirms this hypothesis by showing that voiding dysfunction was 17 times more likely in patients with an absent or weak contraction strength score of 0 or 1 than in those with a score of 2 to 5. Patients with a urogenital hiatus of more than 5 cm were 3 times more likely to have incomplete emptying. There was also a strong correlation between GH size and pelvic muscle weakness (supplementary table 1, http://jurology.com/). Pelvic floor muscle dysfunction affects women of all ages. Muscle dysfunction can present as chronic pelvic pain, dyspareunia or rectal pain. Pelvic muscle weakness seems to affect the patient ability to coordinate the urethrovesical reflex of normal voiding function with poor ability to contract and relax the striated urethral sphincter. Dysfunction in any pelvic floor muscle group can be described in terms of low or high tone. Low tone pelvic floor muscle Table 2. OR of predictors selected by cross-validation
Minimum Quartile 1 Median Mean Quartile 3 Max
Age OR
PVR OR
Levator Strength OR
0.9905 0.9967 0.9969 0.9969 0.9972 1.0050
3.3833 3.9552 3.9778 3.9983 4.0027 4.9741
17.9201 18.4860 18.5495 18.7443 18.7254 21.9531
606
UROGENITAL HIATUS AS RISK FACTOR FOR EMPTYING DISORDERS AFTER PROLAPSE REPAIR
dysfunction occurs when the muscles are weak and unable to contract. This is commonly associated with POP and SUI. High tone pelvic floor muscle dysfunction occurs when the muscles are chronically tense and lose the ability to relax. This is commonly associated with chronic pelvic pain, irritable bowel disorder and painful bladder syndrome.23 We included in the study only patients with POP and SUI with a high prevalence of pelvic floor muscle weakness. There are numerous clinic scales to evaluate pelvic floor muscle dysfunction, of which the most commonly used is the modified Oxford scale.14,15 It has been reproducible among examiners and was recommended to assess pelvic muscle integrity.24 Aging and parity are associated with fibrosis, variations in fiber diameter and centralization of nuclei in the levator ani muscle.25 In our study age and preoperative PVR were associated with voiding dysfunction. However, multivariate analysis revealed that preoperative pelvic muscle strength and preoperative high PVR were the most independent predictors of postoperative voiding dysfunction in patients with POP. To our knowledge this study is the first to correlate pelvic floor muscle weakness, genital hiatus size and incomplete bladder emptying. As our understanding of female voiding mechanisms increases, combining all parameters may enhance the predictive value of detecting postoperative voiding dysfunction. Further research to identify the biological mechanisms responsible for this association and a prospective study with external validation are needed to confirm the strength and generalizability of the associations.
Strengths of this study include application of the Oxford scale and POP quantification. Each technique is easy to use and has good reproducibility. The sample size of 73 patients with incomplete bladder emptying was sufficient to provide relatively precise estimates. Patients with weak pelvic muscles, high PVR and a large genital hiatus should be counseled about the increased risk of incomplete bladder emptying and prolonged postoperative catheterization. This would allow those at high risk to be taught clean intermittent selfcatheterization. Limitations of the current study include its retrospective nature. An optimal definition of postoperative emptying disorders is lacking but increased PVR greater than 100 ml is considered abnormal by most physicians. We could not address whether pelvic floor weakness was due to levator ani neuromuscular disruption, fibrosis or atrophy. Digital magnetic resonance imaging or ultrasound may be done to assess the different components of the levator ani muscle and their individual structural integrity.
CONCLUSIONS Levator contraction strength (0 or 1) and PVR greater than 100 ml were the independent predictors most associated with early emptying disorders. Patients with absent or flicker levator contraction strength should be counseled that they are at high risk for short-term voiding dysfunction. However, most cases of postoperative emptying disorders are self-limited and do not require further surgical intervention.
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