Multiple measurement of resting urethral pressure profile (UPP) was recommended in order to obtain a satisfied urodynamic result. The study aims to find out whether a repeated measurement of resting UPP is necessary in assessing female urethral condition.

Adult women with persistent LUTS or those with stress urinary incontinence (SUI) before an anti-incontinence surgery were recommended for urodynamic studies, before which an informed written consent was obtained from patients as a routine. The written consent announced that the data in the examination could be used in further analyses for clinical research purposes. And an Institutional Review Board Approval was not needed for the study. The technique, definitions and units of the urodynamic measurement conformed to the standards proposed jointly by the ICS and the International Urogynecological Association [1]. In a brief, following Pressure-flow study (PFS) UPP was performed at a half-full bladder with a patient in a semi-lithosupine position, using MMS Solar urodynamic equipment with external pressure transducers. Pressure channels were zeroed to the atmosphere with water transducer holder at symphysis pubis level. The UPP was performed with a F8 dual-lumen water-filled catheter, of which one lumen for measuring the bladder pressure (Pves) with a terminal hole, and the other lumen for measuring the urethra pressure (Pura) with a side hole, 5 cm from the distal one. The urethral and vesical lumen openings should be positioned in the bladder before running the puller, which could be confirmed by checking that the Pura and Pves are almost equally elevated when the patient had a cough. Using a MMS automatic catheter puller, the catheter mounted was pulled out at the rate of 1 mm/s, which was used to calculate the length of the urethra and the related UPP parameters. All the patients had two tests of UPP with the sterile physiological saline solution at a room temperature infused through the urethral lumen at the infusion rate of 1 ml/min. Statistical analysis of the UPP parameters between the two measurements was conducted with the commercial available statistical software (SPSS 16.0) using paired-sample T test on a two-tailed basis with values considered significant at P<0.05.

37 women, with a mean age of 57.27±15.79 year (range: 18–86 year), are included in the study. 22 (59.46%) are clinically diagnosed as SUI. 11 (29.73%) patients are diagnosed as BOO and 5 (13.51%) had DI by PFS. The mean maxim flow rate is 11.28±7.45 (ml/s) (0- 30ml/s). 8 patients refused to take the second UPP due to uncomfortable experience in PFS. 7 were failed to get satisfied curves due to severe damaged urethral competence and urine leakage (3) and DI (4). The remaining 22 patients had got consistent UPP curves and the corresponding parameters were analyzed, although there were bladder dysfunction including urgency (1), hyporefexic bladder and urine retention (>50ml) (8) and other conditions including transurethral resection of bladder neck two years ago (1) and catheterization for more than 3 days before examination (5). 12 patients had MUCP>60cmH2O with a mean of 107.83±31.94 cmH2O. No Statistically significant difference is found between the corresponding parameters from the two measurements.

PFS is now used widely and accepted as an international standard in the diagnosis of Bladder Outlet Obstruction (BOO) for men with BPH, but the criteria, especially for women, have yet to be determined [2]. When a patient could not produce urinary flow in a PFS, UPP are used as one of alternative methods to evaluate the possibility of BOO. Resting UPP has long been utilized in the evaluation of urethral resistance [1] but it is vulnerable to physiologic and technical artifacts that must be minimized to produce technically accurate and clinically meaningful results. Inherent pitfalls of UPP have been drawbacks in its application, and accordingly its use in the assessment of BOO has been in dispute. Nevertheless, resting UPP is a routine preoperative test in many urodynamic laboratories, including ours. To compensate the inherent deficiency, it is recommended that at least two tests of UPP measurement are applied before corresponding parameters are reported correctly. But experience has shown that the parameters from a repeated UPP are usually as the same as those from the previous one. Another situation is that UPP curves or parameters are not easy to be obtained due to damaged urethra in women with SUI or irritable urethra, but a repeated measurement may overcome the condition.
More than half of the patients in the study are with SUI. Most UPP parameters have been used in the evaluation of patients with SUI. Lower values of fields under the UPP curve, for an example, could suggest a greater degree of urethral closing mechanism deficiency and the coexistence of the external sphincter insufficiency. However some thought the routine use of resting UPP has no added value in terms of the prediction of success of anti-incontinence surgery [3].  
The reason for the recommendation of multiple measurement of UPP is based on one assumption that the contraction of pelvic floor muscle during the examination may influence the urethra pressure, which is partly caused by the strength of muscle tissue around the urethra. From our data and experience, we didn’t find this influence. But other artifacts were found in the study. The UPP is usually influenced by the compromised condition of the bladder and urethra. As it is named, resting UPP is performed while the patient is at rest in which no contraction of bladder, urethra and even abdomen is permitted. However the involuntary events are not preventable that is testified by the presented results in the study. The severe damaged urethra caused the decreased capability of the urethra to hold the urine and it was difficult to produce a satisfied UPP. It is the same for an unstable bladder which dramatically influences the UPP results. A patient with OAB and urodynamiclly confirmed DI had an abnormally elevated pressure on the UPP curve, and the following automatically calculated parameters are changed accordingly.  In this situation, a satisfied UPP curve might be obtained in the second or even the third measurement.

Our results show that when a satisfied and explainable UPP curve is obtained, it is unnecessary to repeat another UPP examination, through following another insertion and withdraw of catheter, in order to avoid the possibility of urethral injury and inflammation.

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