Int Urogynecol J DOI 10.1007/s00192-015-2737-2
Abdominal strength in voiding cystometry: a risk factor for recurrent urinary tract infections in women Jesus Salinas 1 & Miguel Virseda 2 & Santiago Méndez 3 & Pablo Menéndez 4 & Manuel Esteban 2 & Jesus Moreno 1
Received: 29 December 2014 / Accepted: 5 May 2015 # The International Urogynecological Association 2015
Abstract Introduction and hypothesis Recurrent urinary tract infections are a common condition in women. The aim of this study is the evaluation of lower urinary tract dysfunctions that are risk factors for recurrent urinary tract infections in women. Methods We conducted a case–control study in 49 women with recurrent urinary tract infections (rUTIs) and 49 control women without rUTIs, comparing the urinary symptoms and urodynamic data of both groups. Results The main significant differences between these groups were age (the women were older in the control group) and the value of abdominal pressure during voiding cystometry (this was higher in the group with rUTIs). After controlling age as a confounding factor, it was confirmed that the value of maximum abdominal pressure during voiding was the only factor to facilitate the rUTIs and the ideal cutoff was 28 cm H2O. Conclusions Abdominal strength in the voiding phase constitutes a risk factor for recurrent urinary tract infections in women.
Keywords Abdominal pressure voiding . Recurrent urinary tract infection . Urodynamics * Jesus Salinas [email protected]
Urology Department, San Carlos Clinico Hospital, Complutense University, Madrid, Spain
Urology Department, Paraplegics National Hospital, Toledo, Spain
Urology Department, Hospital Sanitas La Moraleja, Madrid, Spain
General Surgery Department, Gutierrez Ortega Hospital, Ciudad Real, Spain
Introduction Recurrent urinary tract infections (rUTIs) are a common condition in women. Some of the risk factors for rUTIs were considered, for example: autoimmune and intrinsic risk factors , the level of estrogen, and extrinsic factors such as birth control, sex and dietary  habits. Others pathological conditions promoting rUTIs are spinal cord injury, the presence of urinary catheters, diabetes mellitus, urological abnormalities, and immunodeficiencies diseases . In women rUTIs are associated with organic lesions such as urethral strictures and bladder stones . The influence of lower urinary tract dysfunction (LUTD) on recurrent urinary tract infections in women is not clear . Lin et al.  found an association in diabetic women between recurrent urinary tract infections and urinary disorders (i.e., urinary stress incontinence, detrusor overactivity, increased bladder sensation, and impaired bladder function). However, in all these transversal studies of women with rUTIs there was no control group. It will be important to ensure that there is a relationship between these lower urinary tract dysfunctions and rUTIs. The aim of our study is to evaluate if lower urinary tract dysfunctions (stress urinary incontinence, detrusor overactivity or voiding disturbances) might be risk factors for recurrent urinary tract infections in women, comparing the prevalence of these lower urinary tract dysfunctions in a group of women with rUTIs and a control group of women without this pathological condition.
Materials and methods This case–control study integrates a sample of 49 women with recurrent urinary tract infections (cases) and 49 women without recurrent urinary tract infections (controls), who had been
Int Urogynecol J Table 1
Comparison of the distribution of urinary symptoms between groups
Daytime voiding frequency Nocturnal voiding frequency Stress urinary incontinencea Urinary urgencya Urgency incontinencea Voiding difficultya Decreased urinary voiding stream† a
No LUT infections
2.6±1.40b 2±2c 1.7±1.59b 1±3c 57 %
2.4±1.11b 2±1.38c 1.8±1.52b 2±2c 63 %
73 % 63 % 11 % 70 %
0.137 0.413 0.113 0.208
57 53 24 57
% % % %
Percentage of patients with the symptom
Mean±standard deviation (number of times)
cystometry, and pressure flow study. The polygraph used was Uro 2000 (MMS, Enschede, The Netherlands), according to the specifications of the ICS  and the protocols of Good Urodynamic Practices (GUP) . Patients were placed in a sitting position and proceeded to bladder filling through a 8Fr two-way transurethral catheter, with saline solution at room temperature at a rate of 50 ml/s. Abdominal pressure was recorded by a transrectal balloon catheter and abdominal and bladder pressures were measured with reference to the atmospheric pressure. The filling phase was over when the patient reported a strong desire to void or registered a terminal involuntary detrusor contraction and these were recorded following urodynamic parameters according to ICS standardizations : cystometric bladder capacity, detrusor pressure at the end of the filling phase, the presence of involuntary detrusor contractions, voiding residual urine volume in uroflowmetry, maximum flow rate in the free
referred to the urodynamics unit. Recurrent urinary tract infection was considered if they had occurred at least three times per year; they were characterized by the presence of lower urinary tract symptoms (LUTS; frequency and pain when voiding) associated with positive urine culture (>105 colonies/ml), separated by a symptom-free period of at least 1 week. This definition included reinfection with different bacteria, and relapses with the same strain . To calculate the required sample size, based on data published by Yang and Huang  a significant percentage of at least 50 % of patients with abdominal straining in the rUTI group were considered, versus 20 % in the control group. It was considered that 44 patients were needed in each group to obtain a significance level of 5 % and a bilateral 80 % statistical power. The patients underwent a medical questionnaire, investigation of the presence of LUTS, and urodynamic study, according ICS guidelines. The urodynamic study included flowmetry,
Comparison the distribution of urinary symptoms between groups LUT infections
No LUT infections
Free uroflowmetry volume (ml)a Post-micturition residuala Maximum flow rate (Qmax)a EMG activity during free uroflowmetryb Cystometric bladder capacity (ml)a
303±172.5 21±46.94 20±9.4 81 % 247±99.2
269±123.5 13±29.5 19±10.4 91 % 224±67.7
0.278 0.328 0.615 0.215 0.175
Filling detrusor pressure (cm H2O)a Involuntary detrusor contractionsb Maximum flow rate (Qmax) in test pressure flow (ml/s)a Detrusor pressure at Qmax in test pressure flow (cm H2O)a Maximum abdominal pressure in test pressure flow (cm H2O)a
14±13.3 31 % 20±21.0 26±14.6 37±18.6
11±8.1 35 % 18±9.5 32±23.6 28±24.5
0.259 0.830 0.447 0.193 0.040^
Mean±standard deviation (number of times)
Percentage of patients with the symptom
Int Urogynecol J Table 3
Results of multivariate logistic regression analysis
Variable Age Maximum abdominal pressure Constant
0.006 0.022 −1.089
0.015 0.011 1.059
0.712 0.045* 0.304
uroflowmetry, and pressure flow study: pressure at maximum flow and maximum abdominal pressure during voiding. Uroflowmetry was evaluated on a disk flowmeter. Statistical analysis was performed using the SPSS version 12, and consisted of the following tests of statistical significance: Fisher’s exact test for dichotomous variables and mean comparison test for independent groups (Student’s t test). A diagnostic yield curve maximum abdominal pressure and stepwise multivariate logistic analysis were also developed. The significance level was set at 95 % bilateral and the results are expressed as mean±standard deviation. The project was approved by the Ethics and Research Committees of the San Carlos Clinical Hospital (Madrid, Spain).
Results The age of the patients with UTIs was 54±17.1 years. The age of the control group was 60±12.4 years and differences were significant (p=0.041). There were no significant differences in urinary symptoms reported by patients in the two groups (Table 1). Distribution of urodynamic data for both groups is shown in Table 2. The parameter that showed significant urodynamic differences was maximum abdominal pressure in the voiding phase. In multivariate analysis it was found that the maximum abdominal pressure was the only variable that independently influenced the urinary infection (Table 3). Figure 1 shows the result of the diagnostic performance curve of maximum abdominal pressure in the voiding phase in patients with urinary infection. The ideal cut-off point (maximal sensitivity and specificity) was at 28 cm H2O.
experimental study using a random assignment of exposure to these risk factors. As this is often not possible, an alternative is to perform a case–control study. This type of study has its limitations, mainly in the selection of the control group, which should be representative of this population. A technique used to avoid bias is the pairing of cases according to some variable to be controlled, such as age. However, when this is a continuous variable is difficult to obtain a perfect match, as occurred in our series, in which the women in the control group were older than the rUTI cases. Fortunately, we used multivariate techniques that allowed us to control this confounding factor. In our study we found no relationship between urinary symptoms and the presence of rUTIs. Other authors, such as Timur-Taşhan et al. , reported a prevalence of urinary symptoms 2.9 times higher in women with rUTIs. However, the study involved a population-based sample and it is unclear which criteria the authors used to define rUTI. In a case–control study in which premenopausal women with repeated urinary infections were compared with a group of women with stress urinary incontinence who did not have rUTI, Arya et al.  reported that women with rUTIs had a higher daytime voiding frequency and a lower bladder sensory threshold, but they did not find any other lower urinary tract 1.0
In our series, the only variables that were associated with the presence of rUTIs were age (which was lower in the group with rUTIs), and maximum abdominal voiding pressure (which was higher in the group with rUTIs). Multivariate analysis showed that the only independent variable was maximum abdominal pressure when voiding. To determine the risk factors for developing recurrent urinary tract infections, the most accurate design is an
1 - Specificity Fig. 1 Receiver operating characteristic (ROC) curve analysis. Maximal abdominal pressure
Int Urogynecol J
dysfunctions that were different between the groups. It is possible that premenstrual women with rUTIs have greater urinary frequency. These authors conducted a study pressure/ flow to evaluate the voiding phase. There are no studies that clearly determine the association between lower urinary tract dysfunction in the voiding phase and rUTIs. In a study with a small number of patients, the voiding residual urine explains 13 % of recurrent infections . This factor also assumes a risk of urinary tract infections in other populations, such as patients with spinal cord injury , although this condition does not constitute a risk factor in this and other studies . Athanasiou et al.  found that a decrease in urinary flow is associated with the presence of urinary tract infections in women, but did not find any urodynamics data to prevent rUTI. The association between urgency and urge incontinence in women found by some authors could explain the higher maximum abdominal pressure in the voiding phase in rUTIs, because urge is associated with a hypoactive detrusor, and therefore, with abdominal straining . In women, the abdominal straining is a common condition in the voiding phase. A study by Pauwels et al.  found that 41 % of middle-aged women without urinary symptoms used abdominal pressure to urinate. Some authors do not consider this type of urination as pathological. Yang and Huang  found no differences in the urinary symptoms or other LUTD in premenopausal women, with or without voiding with abdominal pressure, taking the cut-off as abdominal pressure above 10 cm H2O during micturition. However, these authors found a high urethral resistance in postmenopausal patients performing micturition with abdominal strength and conclude that the abdominal pressure might be a way of overcoming urinary obstruction. However, the mechanism can be the contrary, since it has been found that abdominal pressure compresses the female urethra, increasing its resistance [18, 19]. This transmission of abdominal pressure would not occur in men because of the interposition of the prostate tissue, which would justify the lack of an impact of abdominal pressure voiding in men with prostatic hyperplasia . In our study we found that the abdominal pressure to void is a risk factor for rUTI in women and this risk increases when abdominal pressure is greater than 28 cm H2O. The mechanism is similar to that described by Lapides and Costello  or Siroky . They suggest that the high detrusor pressure compresses the bladder wall, resulting in ischemia. This ischemia is favorable to infections, because it facilitates the adherence of bacteria to the urothelium via their fimbriae or flagella. Similarly, our study also indicates that high abdominal pressure during the voiding phase is favorable to infection. In conclusion, abdominal strength in the voiding phase constitutes a risk factor for rUTI in women. It is not clear that this therapeutic application urodynamic data involved and
further studies are needed to confirm this hypothesis and to study its therapeutic usefulness. Conflict of interest The authors declare that they have no conflict of interest.
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