Female obstruction after incontinence surgery may present different urodynamic patterns

Transcription

1 Int Urogynecol J (2013) 24: DOI /s x ORIGINAL ARTICLE Female obstruction after incontinence surgery may present different urodynamic patterns Paulo Rodrigues & Flávio Hering & Eli Cielici Dias Received: 15 August 2011 /Accepted: 16 June 2012 /Published online: 3 July 2012 # The International Urogynecological Association 2012 Abstract Introduction and hypothesis The aim of this study is to report a novel understanding of the urodynamic parameters used to diagnose iatrogenic female obstruction. There is no consensual definition of infravesical obstruction in women. Numerous criteria were designed with arbitrary cutoff values with poor clinical correlation. In order to determine the urodynamic profile of infravesical female obstruction we restricted our analysis to women who acquired voiding disturbances after being submitted to stress urinary incontinence (SUI) surgery. Methods A total of 302 women developed obstructive symptoms or voiding difficulties after SUI operations: 176 cases had had Kelly-Kennedy operations (58.2 %), 50 had had Burch operations (16.5 %), 37 (12.2 %) had had anterior colporrhaphy + abdominal (Burch) operations, 33 (10.9 %) had had sling operations, and 8 (2.6 %) had had Marshall- Marchetti operations. Obstructive urinary symptoms started in days after the operation and urodynamic evaluations were done after various periods of time (median 18.4 months). Clinical presentations varied widely with irritative symptoms predominating the picture. Results Five patterns of pressure-flow relationships could be identified: (1) elevated pressure and poor flow (7.2 %), (2) normal pressure and poor flow (41.5 %), (3) normal pressureandflowassociatedwithprolongedflowtime P. Rodrigues : F. Hering : E. C. Dias Division of Neurourology and Voiding Disturbances, Beneficência Portuguesa Hospital of São Paulo, São Paulo, Brazil P. Rodrigues : F. Hering : E. C. Dias Hospital 9 de Julho of São Paulo, São Paulo, Brazil P. Rodrigues (*) Rua Teixeira da Silva 34-1 Andar - Conj 11, CEP São Paulo, Brazil paulortrodrigues@uol.com.br (24.2 %), (4) poor detrusor contraction and elevated residual volume (12.9 %), and (5) elevated pressure and high flow (14.5 %). No relationship was established amongst the group and the Urinary Distress Inventory questionnaire. Conclusions Infravesical obstruction in women does not fit a single model. As suggested, obstruction in women must be based on broad clinical pictures and urinary complaints. Keywords Obstruction. Incontinence. Urodynamic. Voiding dysfunction. Sling Introduction Urethral suspension or compression by slings for correction of stress urinary incontinence (SUI) may promote urethral obstruction in women due to excessive restriction of the luminal urethra. Frequently overlooked, iatrogenic female urethral obstruction is a real entity due to the increased number of anti-incontinence operations nowadays. As in men, female urethral obstruction is easily recognized when it presents the classic findings of poor stream and elevated detrusor pressure. However, many cases of female obstruction do not fulfill those parameters although the clinical condition strongly suggests it due to the emergence of symptoms just after the operation. Although urinary retention represents the dramatic endpoint of the spectrum, multiple intermediary grades of obstruction may occur after urethral suspension with some cases taking more than 10 years before a diagnosis is made and surgical relief is provided [1]. Indirect evidence of female obstruction is provided by poor stream, necessity of bending or standing to void, straining, dysuria, frequency, nocturia, or urgency which are frequently relegated to being considered unimportant symptoms by some surgeons if the patient can void and does not leak at stress.

2 332 Int Urogynecol J (2013) 24: The non-consensual urodynamic parameters to diagnose female obstruction lead to underreporting of this condition with a few obstructed cases referred for urethrolysis leading to permanent voiding dysfunctions and irreversible damage to the detrusor function that must be recognized and corrected as soon as possible [2, 3]. Voiding difficulty acquired after bladder suspension operations is a unique clinical model to study urodynamic patterns of acquired female obstruction and its variations. The difficulty in recognizing obstruction stems from the scattered detrusor response after imposed infravesical obstruction leading to different pressure-flow relationships not clearly stated and standardized as is the case for men [4]. In this paper we originally collected a selected pool of patients with clinical experience of female voiding dysfunctions suggesting obstruction acquired after anti-incontinence operations and analyzed them from a novel urodynamic perspective. Materials and methods Of 7,300 women presenting for urodynamic evaluation at two reference centers, 574 were selected because of voiding dysfunctions with predominantly obstructive symptoms reported as sensation of incomplete emptiness, poor stream, and straining or bending to void. All patients underwent physical examination with complete history and dynamic inspection of the genitalia in the standing and sitting positions to rule out genital prolapse or any other obstructive causes. They were asked to complete the Urogenital Distress Inventory (UDI). After obtaining a noninvasive flow complete urodynamic evaluations were performed using 6 F double lumen catheters. Transducers were set to atmosphere equals zero at the level of the symphysis pubis. A 9 F rectal catheter was introduced and post-void residual volume was determined at each cycle. Sterile saline fluid at 37 C was used for filling at a rate of 50 ml/min until the patient manifested a desire to void. Flow curve shape, detrusor pressure at maximum flow rate (P det Q max ), maximum urinary flow (Q max ), delay time to start intubated flow (T delay Q) after clinical manifestation of fullness, flow time (Q time ), and final actual residual volume (Vol res ) were prospectively and manually analyzed to minimize flow spikes. Bladder capacity less than 150 ml was also an exclusion criterion. Detrusor activity >5 cmh 2 O was considered overactive bladder. Clinical presentation of the studied population varied as shown in Table 1. For the purpose of comparison 50 cmh 2 O was considered elevated detrusor pressure, while cmh 2 O was considered normal and<20 cmh 2 O determined low detrusor pressure. In the same way manually determined maximum flow above 15 ml/s according to the Liverpool nomogram was considered normal. Table 1 Demographics of 302 cases presenting with clinical evidence of female obstruction after surgical treatment for SUI Characteristic All data are presented according to descriptive statistics as mean and standard deviation (SD). Pearson s index was used for the correlation of the symptoms. Results Value Mean age (years) ± SD (range) 48.2±5 (28 67) Mean parity (number) ± SD (range) 1.8±0.2 (0 6) Time to start of symptoms (days) ± SD (range) 93±56 (1 5,760) Time to presentation (months) ± SD (range) 43±8 (7 240) Kelly-Kennedy 174 cases (57.6 %) Burch 51 cases (16.8 %) Kelly-Kennedy + Burch 36 cases (11.9 %) Sling 33 cases (10.9 %) Marshall-Marchetti 8 cases (2.6 %) Of the 574 supposedly obstructed women, 338 developed voiding difficulties immediately after the operation for SUI. Of those, 36 cases were ruled out due to stage II prolapse or higher leaving 302 selected cases (mean age 48.2±5). Of the patients, 176 underwent Kelly-Kennedy plication, 50 Burch, 37 Burch and concomitant Kelly-Kennedy suspensions, 33 sling suspensions and 8 Marschall-Marchetti (Table 2). Twenty-two cases had had prolonged urinary retention (>7 days). Only six cases with permanent urinary retention demanded surgical relief despite self-catheterization trials, all of whom submitted to sling techniques. Table 2 Clinical presentation in 302 selected female patients presenting for urodynamic evaluation Presentation No. of cases Urinary retention 6 (2.0 %) Poor stream 64 (21.2 %) Straining to void 35 (11.5 %) Sensation of incomplete emptiness 23 (7.6 %) Bending to void 42 (13.9 %) Interrupted flow 15 (4.9 %) Dysuria 30 (9.9 %) Frequency 233 (77.1 %) Urgency (voiding interval 1 h or less) 288 (95.7 %) Recurrent UTI 302 (69.5 %) Nocturia (>2 /night) 189 (62.5 %) Urge incontinence 122 (40.4 %) Some cases presented with more than one leading symptom UTI urinary tract infection

3 Int Urogynecol J (2013) 24: Most of the patients 256 subjects (84.7 %) noticed the emergence of the symptoms in the early postoperative period (from postoperative day 1 to operative day 30, median 12.4 days). However, the majority of them 235 (91.8 %) reported moderate urinary symptoms that increased in bothersomeness as time went by and sought medical help after a median time of 18.4±2 months after incontinence surgery (1 264 months). Surprisingly, only 37 cases (15.7 %) of the former had had the investigation done by the same surgeon who performed the operation. Having had initial conservative or pharmacological treatment patients had urodynamic evaluations after 23.5± 8months. There were no statistical differences amongst the five identified groups and the severity of the symptoms as assessed by the UDI scale (p<0.05). Moreover, symptoms could not predict the pattern of female obstruction (p00.58). The studied population could be grouped into five categories based on the combination of the urodynamic patterns considering P det Q max,q max,t delay to Q max,q time,andvol res. Patients were primarily categorized based on the P det Q max with further grading based on addition of Q max.assomecases did not fit in time to empty the bladder as a sustained detrusor contraction, time to empty was added to the analysis as it might represent a shift in the way the detrusor power was expended during the voiding cycle. Finally, evident poor contraction represented by straining or high post-void residual constituted the remaining pattern. The patients were categorized into one of five groups: 1. Elevated pressure and poor flow (classic): This pattern was shown by 22 cases (7.2 %). The detrusor pressure was high (average 68±7 cmh 2 O, range ) and the maximal flow was low (average 11.4± 1.1 ml/s, range 0 10), time to start flow rate was 14± 7 s on average (range 4 96) and voiding time was 34± 14 s. These cases did not show a significant residual volume (average 14±10 ml, range 0 110). 2. Non-elevated pressure and poor flow: This pattern was presented by 123 cases (41 %). The detrusor pressure was nearly normal (average 35±6 cmh 2 O), but the maximal flow rate was low (average 8.8±2 ml/s); 78 % had residual volume<100 ml and 32 % had residual volumes less than 50 ml; time to start flow was 9±8 s on average and total voiding time was 33±28 s. 3. Non-elevated pressure and poor flow but with prolonged flow time: Seventy-three patients (24.2 %) voided with markedly extended flow rate and sustained detrusor contraction. The maximum flow rate (average 18.9±4 ml/s) and the detrusor pressure at Q max (average 28±7 cmh 2 O) were not elevated staying within the normal range, but the duration of the urinary flow was excessively extended (average 59±32 s) in comparison to the above patterns. Additionally, time to start flow was 6±6 s and final post-void residuals were irrelevant (13±5 ml). 4. Poor detrusor contraction: This group comprised those who voided for the most part by straining (39 cases, 12.9 %). The average maximal flow rate was 5.9±6 ml/s and the average flow time to total void was 79±43 s. In 31.5 % of these cases detrusor pressure could be detected (9±12 cmh 2 O), although maximization of the flow was attempted by using the abdominal muscles. Twenty-six cases (9.2 %) were only able to void exclusively by straining. This group exhibited the highest residual volumes (average 130±110 ml). No special interest was taken of time to start flow since many cases initiated it by voluntary command through a Valsalva maneuver. 5. Elevated pressure and high flow: In this group encompassing 44 cases (14.5 %) the detrusor pressure was high (average 56±15 cmh 2 O) and the maximal flow was above the 25th percentile on the Liverpool nomogram (average 14±5 ml/s). In this final group 6 % had maximal flow rate above the 75th percentile, 52 % were between the 50th and 75th percentile, and 42 % were between the 25th and 50th percentile with no residual volume. Time to start flow was 4±4 s and pressure-flow voiding time was 38±13 s (Tables 3 and 4). Discussion The definitions and nomograms that are used to describe bladder outlet obstruction (BOO) in men are not suitable for women. What is normal voiding pressure and flow rate in men cannot be applied to women. While the Abrams- Griffiths nomogram for men was devised based on the clinical presentation and response to treatment of men with BOO with good clinical correlation, the lack of association of the pressure-flow plot in symptomatic women may originate from the specific nature of the female urethra with its short and distensible conduit walls surrounded by active and passive elements that influence the flow through it. Without a clear association between pressure and flow a cutoff value for obstruction is imprecise in women. The increase in anti-incontinence surgeries and the iatrogenic obstruction that can result from the treatment of SUI has cast light on disorders of micturition in women. Indeed, BOO resulting from a number of conditions seems to be as fairly common in women as in men presenting for evaluation of lower urinary tract symptoms (LUTS). Recognizing those at risk of having BOO and understanding how to best diagnose this condition are essential steps in identifying therapies that are most likely to provide long-lasting benefit.

4 334 Int Urogynecol J (2013) 24: Table 3 Proposed new five condensed urodynamic diagnostic patterns observed in 302 obstructed women P det Q max (cmh 2 O) Q max (ml/s) Res (ml) Time to start flow since the contraction (s) Total flow time (s) Pattern 1 High Low Irrelevant Irrelevant Irrelevant Pattern 2 Normal Low Low Irrelevant Irrelevant Pattern 3 Normal Normal Absent Irrelevant Extended Pattern 4 Straining Low High Irrelevant Extended Pattern 5 High High Absent Irrelevant Irrelevant It is now well documented that sling operations may carry a relevant risk of urethral obstruction as high as 6.9 % in Medicare beneficiaries with a suspicious incidence of 30.5 % use of urodynamic teting in the first year after operation as an indicator of possible complications or unexpected clinical results [5]. Female urethral obstruction is easily recognized when it presents the classic findings of poor stream and elevated detrusor pressure well established for men. Also comparison of the pre- and postoperative urodynamic findings may give evidence of the obstructive nature of the surgery imposed on the urethra, but many cases of clinical voiding dysfunctions acquired after surgical manipulation of the urethra do not fulfill those parameters although the clinical suspicion of female obstruction is evident. As this complaint may demand therapy to provide relief, it is important to have established parameters that may allow recognition of obstruction. Unfortunately, as stated by Rosenblum and colleagues in nulliparous young women with LUTS, the majority of women found to have a dysfunctional voiding phase on urodynamic testing did not have a chief complaint of voiding or obstructive symptoms [6] impeding the diagnosis of obstruction based solely on clinical complaints as in our series. Likewise, Lemack and Zimmern also found that only half of patients who were urodynamically obstructed (43.9 %) reported moderate or great difficulty with bladder emptying as assessed by the UDI questionnaire [7]. Moreover, a normal flow pattern such as the bell-shaped one or assumed normal values for flow rate in women do not exclude voiding difficulties [8, 9]. It is estimated that 5 20 % of surgeries for SUI present urethral obstruction; however, this number may vary widely depending on the criteria used to identify urethral obstruction [10]. Although the exact mechanism of SUI correction after urethral suspension remains to be elucidated, it was verified that sling operations do change the relationship between flow and detrusor pressure as noted by Lukacz and colleagues who described a change in maximum non-intubated flow rate from 28.6 to 16.3 ml/s after tension-free vaginal tape (TVT) along with a significant, but perhaps less meaningful, increase in detrusor pressure of 4 cmh 2 O during maximum flow [11]. Despite the fairly dramatic reduction in maximum flow rate, no subjective changes in voiding function were apparent in their study meaning that urodynamic evidence of urethral constriction may not be related to clinical perception, while at the same time the inverse may also be true that some patients may develop an important clinical picture with mild or moderate urodynamic changes if based on the actual way of looking for female urethral obstruction. This led us to conceive urethral obstruction as a composite of parameters abandoning the old tradition of measuring detrusor pressure and flow rate as a surrogate to obstruction as applied to men. Moreover, most of the papers concerning female obstruction clearly demonstrated significant overlap of voiding and residual parameters among obstructed and control cases with an enormous range and large standard deviation for each parameter reducing the statistical significance and limiting the use of cutoff parameters, hence prompting us to abandon the traditional way of looking at urethral obstruction. As stated by Nitti et al. [12], female obstruction may only be diagnosed by visualizing the obstruction by fluoroscopic monitoring during voiding on urodynamic studies since no single test can clinch and confirm the diagnosis. Although they focused on the visual appearance of the outlet during sustained detrusor contraction to establish obstruction, obstructed women on fluoroscopy presented lower Q max (9.0 versus 20.1 ml/s) and higher P det Q max (42.8versus22.1cmH 2 O) than the remainder of the women studied. To them the surgical event associated Table 4 Urodynamic parameters for the five described patterns in 302 obstructed women n (%) P det Q max (cmh 2 O) Q max (ml/s) Res (ml) Time to start flow since the contraction (s) Total flow time (s) Pattern 1 22 (7.2 %) 68±7 5.9±1.1 14±10 14±7 34±14 Pattern (41 %) 35±6 6.2±2 <100 9±8 33±28 Pattern 3 73 (24.1 %) 28±7 11.9±4 Absent 6±6 59±32 Pattern 4 39 (12.9 %) 9±12 or straining 5.9±6 130±110 Irrelevant 79±43 Pattern 5 44 (15.5 %) 56±15 14±5 Absent 4±4 38±13

5 Int Urogynecol J (2013) 24: with voiding difficulties is the landmark for iatrogenic female obstruction as also claimed by Amundsen et al. who stated that if the clinical picture for female obstruction is clear enough after anti-incontinence operation the diagnosis of obstruction is already established between the two whatever the urodynamic result [13]. Sadly, in large series of cases submitted to urethrolysis a hallmark of urethral obstruction will be present with protracted urinary retention, but leaving aside another expressive and undiagnosed number of cases with early postoperative shortterm voiding dysfunctions or with the need for a postoperative intermittent catheterization regimen but who recovered spontaneous voiding afterwards harboring subclinical obstruction, which is poorly studied. Many studies restricted the definition of female obstruction by establishing cutoff parameters for Q max and/or P det Q max [14]. The celebrated nomogram based on 587 consecutive patients from Groutz et al. established female urethral obstruction by the free flow rate<12 ml/s and detrusor pressure at maximum flow>20 cmh 2 O with an inadvertent comparison since the free flow rate was not compared to intubated pressure. In that study in which 26 % of the obstructed cases resulted from previous anti-incontinence surgery, an opportunity was missed to restrict the analysis to a homogeneous group where the obstruction was a certainty [15, 16]. That flaw may explain part of the observation that 20 % of the control cases in that group were classified as obstructed and the overestimation rate observed in the comparison of five diagnostic criteria studied by Akikwala et al. [17]. Additionally, many studies on female obstruction assumed obstruction from predetermined urodynamic parameters [9, 18] or established obstruction from the clinical standpoint before determining urodynamic parameters for obstruction [18] and only then correlating each other. Our assumption of acquired urethral obstruction with clinical manifestation starting just after the operation for SUI provides us with the certainty of only dealing with women whose obstruction was caused by the operation. Contemporary complex calculations using receiver-operating characteristic curves in an attempt to determine cutoff values identified Q max <15 ml/s and P det Q max >20 cmh 2 O as the best predictors of female obstruction [19]. Further refinement of the study by the same group led to determination of a maximum intubated flow rate of 11 ml/s and the corresponding average detrusor pressure of 21 cmh 2 O as the optimal cutoff values to establish the diagnosis of female obstruction. However, the central critical question still remains in all those clinical studies to define parameters for female obstruction because they assumed as obstructed those who complained of voiding difficulties, so to speak, they measured the urodynamic parameters of those clinically obstructed, or better to say suspected of having obstruction, and compared these parameters to a counterpart of non-obstructed cases, either with SUI or volunteers. The uniqueness and the strength of our study was the pool of patients that reported voiding dysfunctions emerging just after the operation for SUI. Our assumption admitted that those patients acquired iatrogenic urethral obstruction since they did not report voiding difficulties before the surgical event, thus avoiding direct comparisons to different populations. Our hypothesis for female obstruction is rooted in the assumption that the female urethra and detrusor muscle behave quite differently than in men after iatrogenic narrowing of the urethra. As correctly stated by Cormier et al. [20], female obstruction cannot solely be looked by traditional parameters but by broad view of the traces, time to void, related post-void residual volume and the combination of flow rate and detrusor pressure. As our patients acquired obstruction from the operation we could separate them into five different patterns of voiding. Only 7.2 % of the obstructed cases matched the traditional pattern of obstruction with high detrusor pressure and low flow rate, an incidence similar to that observed by Blaivas and Groutz of 8.3 % [16] using their proposed nomogram. A high detrusor pressure may exclude a big sample of obstructed women whose detrusor voiding is not able to reach such a magnitude, explaining the reason why the incidence of female obstruction is much lower than it probably is. Surprisingly, the most frequent obstructed pattern in the obstructed women was comprised of those cases with moderate elevation of detrusor pressure but with low intubated flow rate. Those cases seemed to behave as if the bladder could not react to the imposed urethral obstruction with robust muscular response. The reaction of the detrusor pressure produced moderate elevation of the pressure with varied residuals. The moderate increase of the detrusor pressure was based on the assumption that the normal female voiding pressure is around 20 cmh 2 O, which was obtained from previous studies in populations with exclusively SUI [21], noting that it might not reflect a true control since this population has a lower than normal outlet resistance [22]. Similarly unexpected, a significant amount of obstructed women displayed their obstruction without elevation of detrusor pressure or lowering of the flow rate but shifting markedly the time to empty the bladder as already described by Di Grazia et al. as an important sign of female obstruction [18]. This is clinically relevant because some patients spoke of prolonged time to empty the bladder after sling procedures. Their observed voiding time (78.2±52 s) was comparable to ours 59±32 s. Additionally, in that study detrusor pressure was not significantly elevated either (obstructed 27.6 cmh 2 O, control 17.2 cmh 2 O) [18]. Opposite to the above patterns cases where the outlet resistance does equilibrate with the detrusor pressure, in some cases the residual volume may increase markedly demonstrating a fading of the detrusor muscle in its contraction capacity.

6 336 Int Urogynecol J (2013) 24: Finally, there are cases where the clinical picture is explicit but the classic parameters of obstruction are not evident, making the scenario puzzling. The lack of a consensual urodynamic definition of female obstruction explains the varied prevalence from different academic groups. Accordingly, Farrar et al. [23] observed an incidence of only 2.7 % in 6,000 cases, while Nitti et al. [12] reported 29 % in 261 cases using different references which included fluoroscopic visualization of the urethra during micturition. Our novel and original concept of analysis of female obstruction allows a broader characterization of iatrogenic obstruction in a very particular population studied in a tertiary referral center. Our largest studied population in the literature to date and the originality of our study was centered on the evidence of a temporal relationship between new voiding symptoms and anti-incontinence surgery allowing the reverse reasoning of certainty of acquired obstruction, while all the other studies looked for obstruction on the assumption that clinical presentation of obstruction may ascertain its presence. This illustrates the difficulty in diagnosing BOO in women in an absolute manner. Conflicts of interest References None. 1. Basu M, Duckett JR, Papanikolaou N (2008) Retropubic urethrolysis of colposuspension: does it improve voiding and overactive bladder symptoms? J Obstet Gynaecol 28: Leng WW, Davies BJ, Tarin T, Sweeney DD, Chancellor MBJ (2004) Delayed treatment of bladder outlet obstruction after sling surgery: association with irreversible bladder dysfunction. J Urol 172: Segal J, Steele A, Vassallo B, Kleeman S, Silva AW, Pauls R, Walsh P, Karram M (2006) Various surgical approaches to treat voiding dysfunction following anti-incontinence surgery. Int Urogynecol J Pelvic Floor Dysfunct 17: Rodrigues P, Lucon AM, Freire GC, Arap S (2001) Urodynamic pressure flow studies can predict the clinical outcome after transurethral prostatic resection. J Urol 165: Anger JT, Litwin MS, Wang Q, Paschos CL, Rodríguez LV (2007) Complications of sling surgery among female Medicare beneficiaries. Obstet Gynecol 109: Rosenblum N, Scarpero HM, Nitti VW (2004) Voiding dysfunction in young, nulliparous women: symptoms and urodynamic findings. Int Urogynecol J Pelvic Floor Dysfunct 15: Lemack GE, Zimmern PE (1999) Predictability of urodynamic findings based on the Urogenital Distress Inventory-6 questionnaire. Urology 54: Pauwels E, De Wachter D, Wyndaele JJ (2005) A normal flow pattern in women does not exclude voiding pathology. Int Urogynecol J Pelvic Floor Dysfunct 16: Gravina GL, Costa AM, Galatioto GP, Ronchi P, Tubaro A, Vicentini C (2007) Urodynamic obstruction in women with stress urinary incontinence do nonintubated uroflowmetry and symptoms aid diagnosis? J Urol 178: Dunn JS Jr, Bent AE, Ellerkman RM et al (2004) Voiding dysfunction after surgery for stress incontinence: literature review and survey results. Int Urogynecol J Pelvic Floor Dysfunct 15: Lukacz ES, Luber KM, Nager CW (2004) The effects of the tension-free vaginal tape on voiding function: a prospective evaluation. Int Urogynecol J Pelvic Floor Dysfunct 15: Nitti VW, Tu LM, Gitlin J (1999) Diagnosing bladder outlet obstruction in women. J Urol 161: Amundsen CL, Guralnick ML, Webster GD (2000) Variations in strategy for the treatment of urethral obstruction after a pubovaginal sling procedure. J Urol 164: Bass JS, Leach GE (1991) Bladder outlet obstruction in women. Probl Urol 5: Groutz A, Blaivas JG, Chaikin DC (2000) Bladder outlet obstruction in women: definition and characteristics. Neurourol Urodyn 19: Blaivas JG, Groutz A (2000) Bladder outlet obstruction nomogram for women with lower urinary tract symptomatology. Neurourol Urodyn 19: Akikwala TV, Fleischman N, Nitti VW (2006) Comparison of diagnostic criteria for female bladder outlet obstruction. J Urol 176: Di Grazia E, Troyo Sanromán R, Aceves JG (2004) Proposed urodynamic pressure-flow nomogram to diagnose female bladder outlet obstruction. Arch Ital Urol Androl 76: Chassagne S, Bernier PA, Haab F et al (1998) Proposed cutoff values to define bladder outlet obstruction in women. Urology 51: Cormier L, Ferchaud J, Galas JM et al (2002) Diagnosis of female bladder outlet obstruction and relevance of the parameter area under the curve of detrusor pressure during voiding: preliminary results. J Urol 167: Lemack GE, Zimmern PE (2000) Pressure flow analysis may aid in identifying women with outflow obstruction. J Urol 163: Defreitas GA, Zimmern PE, Lemack GE, Shariat SF (2004) Refining diagnosis of anatomic female bladder outlet obstruction: comparison of pressure-flow study parameters in clinically obstructed women with those of normal controls. Urology 64: Farrar DJ, Osborne JL, Stephenson TL et al (1975) A urodynamic view of bladder outflow obstruction in the female: factors influencing the results of treatment. Br J Urol 47: