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Bladder Dysfunction: Diagnosis with Dynamic US¹

¹ From the Radiology Unit of Hospital das Clinical (M.F.T.F.F.), Pediatric Nephrology Unit (E.M.L., T.M.S.), Department of Pediatrics (E.M.A.G.), and Urology Unit (A.C.M., C.R.P.), Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. From the 2001 RSNA scientific assembly. Received November 25, 2001; revision requested February 1, 2002; revision received May 7; accepted October 21. Address correspondence to M.F.T.F.F., Rúa Nicarágua 48, Apt 201, Belo Horizonte, Minas Gerais, Brazil (e-mail: terezafilgueiras@terra.com.br).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
PURPOSE: To evaluate the role of dynamic ultrasonography (US) in the diagnosis of bladder dysfunction and to compare dynamic US with urodynamic study, which is considered to be the standard in the diagnosis of bladder dysfunction.

MATERIALS AND METHODS: Images from 71 pairs of examinations in 63 patients (median age, 7.9 years; range 1.0–17.4 years) were included in the study. After the child consumed adequate fluids in an appropriate environment, natural filling of the bladder occurred, and dynamic US was used to evaluate detrusor activity, determine capacity of the bladder, and estimate residual urine volume. A urodynamic study was performed in every patient within 6 months of dynamic US and under the same treatment conditions. The paired Student t test was used to compare the maximal cystometric capacity values obtained with the two examinations. Analysis of validity was performed with the calculation of sensitivity, specificity, positive and negative predictive values, and their respective 95% confidence limits.

RESULTS: The bladder capacity was not significantly different between dynamic US and urodynamic study (P = .12). Analysis of validity for the determination of the presence of clinically substantial residual urine showed 97.7% sensitivity and 100% specificity for dynamic US. The sensitivity and specificity of dynamic US in the detection of involuntary detrusor contraction were 93.0% and 88.9%, respectively. In the analysis of involuntary detrusor contraction with urine leakage, dynamic US showed sensitivity of 100% and specificity of 97.8%.

CONCLUSION: Dynamic US is a sensitive method for the diagnosis of bladder dysfunction.

© RSNA, 2003

Index terms: Bladder, abnormalities, 83.831, 83.834 • Bladder, US, 83.12981 • Children, genitourinary system • Ultrasound (US), comparative studies, 83.12981, 83.1233 • Urine, incontinence

	INTRODUCTION

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Bladder dysfunction corresponds to abnormalities in the filling with or emptying of urine. Storage defects may be caused by an incompetent sphincter, reduction of bladder compliance, or hyperactivity of the detrusor. Bladder emptying may be impaired by hyporeflexia or hyperreflexia of the detrusor, urethral obstruction due to urethral and periurethral hyperactivity, or organic lesions.

The care of children who have bladder dysfunction requires a multidisciplinary team of physicians because of the variety of associated problems, including neurologic and orthopedic abnormalities and psychological disturbances. The objectives of treatment of neonates and infants are to preserve renal function and prevent urinary tract infection. When treating older children, it is also important to promote urinary continence (1,2). To fulfill these objectives, a correct diagnosis of the alterations of the various stages of micturition is needed.

Ultrasonography (US) has enabled physicians to measure the thickness of the bladder wall, evaluate postvoiding residual urine, and estimate bladder volume (3–6). Some investigators have used US to help them evaluate urinary incontinence caused by stress in women by studying the mobility of the bladder neck (7–9). US has also been used to evaluate bladder voiding in newborns by using maneuvers that induce micturition (10).

With the introduction of urodynamic study and video documentation of the study into clinical practice, much progress has been made in the understanding of the physiopathology of bladder dysfunction and in planning the treatment of patients with this dysfunction (2,11); however, urodynamic study is invasive and is associated with additional drawbacks, particularly in children. The filling of the bladder is not natural and children do not always cooperate. These complications may interfere with the results and impair their interpretation. On this basis, the technique of dynamic US of the urinary tract was developed for use in the evaluation of bladder dysfunction in children and adolescents. In addition to helping physicians measure the thickness of the bladder wall and estimate residual urine volume, this technique also aids in the evaluation of detrusor activity by means of the detection of involuntary contractions, the identification of urine leakage associated with these contractions or not, and the determination of maximum cystometric capacity (MCC) with physiologic bladder filling. Furthermore, through the depiction of indirect signs, dynamic US also permits physicians to evaluate the external urethral sphincter.

The objective of the present study was to evaluate dynamic US for the diagnosis of bladder dysfunction and to compare dynamic US with urodynamic study, which is considered to be the standard for the diagnosis of bladder dysfunction.

	MATERIALS AND METHODS

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Patients
The study was approved by our Institutional Review Board Ethics Committee. Informed consent was obtained either from the parents of younger children or from the older children, and all patients were examined with the assistance and collaboration of their parents. The dynamic US examiner was blinded to the results of urodynamic study, and vice versa.

We compared images from 71 pairs of dynamic US and urodynamic study examinations of 63 children and adolescents (44 girls, 19 boys) with bladder dysfunction. The patients were aged 1.0– 17.4 years (median, 7.9 years) and were examined from March 1996 to July 2001. The eight patients who underwent two pairs of examinations did so at different times and under different treatment conditions. These eight patients were not receiving medication during the first examination, and were taking oxybutin (Retemic; Apsen Farmaceutica, São Paulo, Brazil) during the second examination.

All patients were cared for at the Bladder Dysfunction Outpatient Clinic of the University Hospital of Federal University of Minas Gerais, and we examined 156 patients in this period; however, only 63 patients met the criteria to be included in this study. To be included, patients cared for in the outpatient clinic had to undergo dynamic US and urodynamic study examinations within a 6-month interval and while being treated with anticholinergic medications.

Bladder dysfunction was caused by the following: meningomyelocele in 25 (40%) patients; neurogenic problems, including spina bifida, sacral agenesis, or schistosomotic myelitis in eight (13%) patients; organic abnormalities, primary vesicoureteral reflux, or posterior urethral valve in 15 (24%) patients; and bladder dysfunction without an organic cause in 15 (24%) patients.

Examinations
US was performed with either an SSA 90A instrument (Toshiba, Japan) equipped with 3.75-MHz, 5.0-MHz, and 7.5-MHz transducers or an SSA 340A instrument (Toshiba) equipped with 3.0–6.0-MHz and 8.0–10.0-MHz transducers. The examinations were documented with a video printer and recorded on a videocassette.

Dynamic US was performed by one investigator (M.F.T.F.F.), and each examination required approximately 50 minutes. The dynamic US examination consisted of three stages. In the first stage, which is considered to be of fundamental importance, the patient began to consume fluids 1 hour before the examination to cause natural filling of the bladder. The amount of fluid consumed by infants and toddlers was that habitually accepted by them during each feeding. For older children and adolescents, the amount of fluid consumed ranged from 250 to 600 mL, depending on age, weight, and ambient temperature. Information about the urinary habits of the child was obtained to guide the execution of the examination. Since the desire to void is directly influenced by the emotional status of the child, a welcoming environment complete with toys and books was prepared in both the waiting room and the examining room.

In the second stage of the examination, the phases of bladder filling were studied. The shape and wall of the bladder were imaged, and detrusor activity, the pelvic floor, and the occurrence of urine leakage were analyzed. Involuntary detrusor contraction was identified on the basis of the simultaneous alteration of the shape of the bladder and the aspect of the bladder wall. In the longitudinal sections, the longitudinal diameter decreased, and the anteroposterior diameter increased. In the transverse sections, the bladder changed in shape from quadrangular to rounded, and the bladder wall showed a serrated aspect (Fig 1). When diverticula were present, they filled during the contractions of the detrusor, probably as a consequence of increased intravesical pressure (Fig 2). Contraction of the pelvic floor was identified on the basis of abrupt movements of the bladder neck and pelvic floor in the cephalocaudal direction and was usually associated with either the desire to void or the feeling of urgency (Fig 3).

View larger version (101K): [in this window] [in a new window] [Download PPT slide]   Figure 1a. (a) Longitudinal US images of the bladder show relaxed detrusor (left) and contracted detrusor (right). Simultaneous alteration of the shape of the bladder and the appearance of the bladder wall took place, with an increase in the anteroposterior diameter, a decrease in the longitudinal diameter, and a serrated appearance of the wall (arrow). (b) Transverse US images of the bladder show contracted detrusor (left) and relaxed detrusor (right). The bladder changed in shape from quadrangular to rounded, and the wall appears serrated (arrows).

View larger version (113K): [in this window] [in a new window] [Download PPT slide]   Figure 1b. (a) Longitudinal US images of the bladder show relaxed detrusor (left) and contracted detrusor (right). Simultaneous alteration of the shape of the bladder and the appearance of the bladder wall took place, with an increase in the anteroposterior diameter, a decrease in the longitudinal diameter, and a serrated appearance of the wall (arrow). (b) Transverse US images of the bladder show contracted detrusor (left) and relaxed detrusor (right). The bladder changed in shape from quadrangular to rounded, and the wall appears serrated (arrows).

View larger version (103K): [in this window] [in a new window] [Download PPT slide]   Figure 2a. Longitudinal US images of the bladder. (a) A diverticulum (arrow) is seen in the posterolateral wall of the bladder. (b) Observe the filling of the diverticulum (arrow) during the contraction of the detrusor.

View larger version (89K): [in this window] [in a new window] [Download PPT slide]   Figure 2b. Longitudinal US images of the bladder. (a) A diverticulum (arrow) is seen in the posterolateral wall of the bladder. (b) Observe the filling of the diverticulum (arrow) during the contraction of the detrusor.

View larger version (108K): [in this window] [in a new window] [Download PPT slide]   Figure 3. Longitudinal US images of the bladder. Arrow shows the position of the bladder neck. Left image shows cephalic position of the bladder neck during the contraction of the pelvic floor muscle. Right image shows caudal position of the bladder neck when the pelvic floor muscle is relaxed.

The third stage of the examination consisted of the determination of MCC and of residual urine volume. MCC was considered to be the volume estimated by measuring the bladder when the patient reported his or her desire to void or immediately before spontaneous voiding or urinary leakage. Residual urine volume was calculated by measuring the bladder immediately after urinary leakage or voiding occurred. When the residual urine was substantial, the measurement was also made after a second or third voiding. For the calculation of the volume of bladder capacity and of residual urine, we used the formula for the calculation of an ellipsoid volume (4,5). Residual urine volume was considered to be clinically substantial when its volume was greater than 10% of the MCC or greater than or equal to 20 mL (12).

Urodynamic study was performed by two investigators (A.C.M. and C.R.P.). The time required to perform urodynamic study was about 30–45 minutes. Urodynamic study was performed by using Menuet (Dantec, Skovlunde, Denmark) and Dynapack Uromaster MPX 616 (Dynamed, São Paulo, Brazil) instruments. The routine adopted for the examination consisted of uroflowmetry, cystometry, voiding cystometry, and electromyography with either surface or needle electrodes.

Statistical Analysis
The results obtained were analyzed by using a computer program (Epi Info, version 6.04; Centers for Disease Control and Prevention, Atlanta, Ga) (13). Considering urodynamic study as the standard, an analysis of validity was performed to determine the following parameters obtained with this examination and with dynamic US: presence of residual urine, involuntary detrusor contractions, involuntary detrusor contractions with and without urine leakage, spontaneous urine leakage, and stress-related urine leakage. Sensitivity, specificity, positive and negative predictive values, and their respective 95% confidence limits were calculated for all of these parameters. The paired Student t test was used to compare the mean MCC values obtained with the two examinations. The level of significance was set at 5% (P < .05).

	RESULTS

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Maximum Cystometric Capacity
Of the 71 pairs of examinations, 66 were considered for comparison of the differences in mean MCC obtained with dynamic US and urodynamic study. The measurement of MCC was not performed at urodynamic study of five patients. Mean (± SD) MCC volume obtained with dynamic US and urodynamic study was 214.4 mL ± 112.0 and 200.7 mL ± 110.3, respectively (P = .12).

Residual Urine Volume
The presence of residual urine was detected with dynamic US in 43 patients and with urodynamic study in 44 patients. The validity analysis for this parameter is shown in Table 1.

Stress-related urine leakage was present with both techniques in 15 of 16 patients and absent in 20 of 20 patients, showing a dynamic US sensitivity and specificity of 93.8% (95% CI: 66.7%, 99.7%) and 100% (95% CI: 80.0%, 100%), respectively.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
The major objectives of the treatment of bladder dysfunction are to preserve renal function, promote urinary continence, and provide a better quality of life to the patient (1); thus, it is imperative to make a correct, early diagnosis of changes in the urinary tract of children with bladder dysfunction.

Urodynamic study has greatly advanced the understanding of bladder dysfunction by enabling physicians to diagnose and treat this abnormality. In addition, the parameters evaluated in this examination have begun to be used as predictive factors for the deterioration of the upper urinary tract (14–16). Children tolerate this examination poorly however, since it requires the introduction of two catheters into the urethra and one into the rectum. Furthermore, filling of the bladder is performed artificially with fluid infusion, usually at room temperature and at a faster rate than natural bladder filling. Both the presence of catheters and the rate of fluid infusion can stimulate bladder contractions (17). Several other causes of error are likely to occur when urodynamic study is performed in children, as pointed out by Hjälmas (18) and Wen and Tong (19). The anxiety of the child can impair the precision of MCC and postmicturitional residue measurements as a consequence of voluntary contraction of the abdomen or sphincter. Anxiety may also provoke voiding before the child feels the desire to void or interruption of voiding before complete emptying of the bladder. Excessive bladder filling may also occur in smaller children who have difficulty interpreting the desire to void. If an infant cries, contractions of the abdomen or spontaneous rectal contractions may interfere with the abdominal pressure recordings, a fact that invalidates the measurement of detrusor pressure. Since the urethral diameter in children is small, the insertion of two urethral catheters can cause partial urinary obstruction (18).

In view of these drawbacks of urodynamic study for children and considering that US is a noninvasive method, dynamic US was developed to permit the study of changes present in bladder dysfunction. Thus, by using dynamic US it was possible to determine bladder capacity and residual urine volume and to evaluate the presence of involuntary detrusor contractions, with or without urine leakage. In our investigation of the external urethral sphincter, we observed the presence of spontaneous urine leakage or stress-related urine leakage and the presence of contractions of the pelvic floor.

There was agreement between the two techniques for MCC determination, and dynamic US showed high sensitivity and specificity for the estimation of residual urine volume; thus, dynamic US proved to be a precise method to assist in the evaluation of these two parameters with advantages when compared to urodynamic study. Contributing factors are cooperation of the child, physiologic bladder filling, and avoidance of catheters, which can interfere with bladder filling and emptying. Another advantage is that dynamic US aids in the evaluation of residual urine at one or more times and the determination of bladder emptying in children submitted to clean intermittent catheterization.

The identification of involuntary detrusor contractions is important in making a diagnosis of and planning the treatment for bladder dysfunction. These contractions substantially impair the storage of urine in the bladder and may cause lesions in the urinary tract, especially when associated with detrusor-sphincter dyssynergia and vesicoureteral reflux (15,20). The consequences of these contractions for the bladder are hypertrophy of the detrusor, formation of diverticula, and a reduction in compliance.

The involuntary contractions of the detrusor are frequently accompanied by urine leakage, and, in children with preserved sensitivity, they are accompanied by feelings of urgency, dysuria, and maneuvers and movements of perineal and pelvic floor muscles in an attempt to prevent urine leakage. These symptoms and urine leakage generate anxiety and suffering in the children, reduce their self-esteem, and interfere with their social adaptation and intellectual and emotional development.

With urodynamic study, detrusor activity is identified by measuring detrusor pressure (12). Noninhibited contraction of the detrusor is defined as a sudden and involuntary increase in this pressure, which cannot be inhibited during filling of the bladder (19–21).

With dynamic US, detrusor activity was evaluated by identification of involuntary contraction during bladder filling. Comparison of these contractions detected with the two techniques in 70 examinations showed agreement in 64 examinations (91%). Of the three patients in whom noninhibited contraction was depicted only at urodynamic study, two were younger than 3 years, an age range in which the observation of sporadic involuntary contractions is of no clinical importance (18). Moreover, the crying observed in these two patients during urodynamic study may have triggered the reported noninhibited contraction. The third patient in this group presented only one contraction of low amplitude at 70 mL of bladder filling for an MCC of 260 mL. It is possible that this contraction was caused by either the presence of the catheters in the bladder or the artificial filling of the bladder. Of the three patients in whom contraction was identified only at dynamic US, two were irregularly using an anticholinergic agent, a fact that might have interfered with the evaluation. In the third patient, this contraction occurred only with a bladder volume greater than the MCC observed at urodynamic study, a fact that explains the discordance.

Dynamic US also proved to be effective in the detection of involuntary contractions associated with urine leakage and of urine leakage without detrusor activity.

The recording of bladder pressure and the diagnosis of detrusor-sphincter dyssynergia with urodynamic study are important when determining the risk of damage to the urinary tract and selecting the appropriate treatment. However, indirect signs can be detected with dynamic US. Findings that indicate increased bladder pressure are the reduction or interruption of emptying of the ureter, increased volume of the diverticulum, and substantial variations in the dimensions of the collecting system and the pelvis, associated with a bladder of normal or reduced capacity (Fig 4). The increased thickness of the bladder wall, the presence of diverticula, and a substantial volume of residual urine suggest detrusor-sphincter dyssynergia.

View larger version (115K): [in this window] [in a new window] [Download PPT slide]   Figure 4a. Images show alterations that indicate increased bladder pressure. All images were obtained during the same examination. (a) Longitudinal images of the left kidney show a dilated collecting system (arrow). (b) Bladder features small diverticula. During dynamic US, it is possible to observe the difficulty of emptying the ureter. Arrow indicates the left ureter. (c) Immediately after voiding of the bladder, the collecting system of the kidney is almost empty (arrow).

View larger version (90K): [in this window] [in a new window] [Download PPT slide]   Figure 4b. Images show alterations that indicate increased bladder pressure. All images were obtained during the same examination. (a) Longitudinal images of the left kidney show a dilated collecting system (arrow). (b) Bladder features small diverticula. During dynamic US, it is possible to observe the difficulty of emptying the ureter. Arrow indicates the left ureter. (c) Immediately after voiding of the bladder, the collecting system of the kidney is almost empty (arrow).

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 4c. Images show alterations that indicate increased bladder pressure. All images were obtained during the same examination. (a) Longitudinal images of the left kidney show a dilated collecting system (arrow). (b) Bladder features small diverticula. During dynamic US, it is possible to observe the difficulty of emptying the ureter. Arrow indicates the left ureter. (c) Immediately after voiding of the bladder, the collecting system of the kidney is almost empty (arrow).

Dynamic US is also useful in the approach of urinary tract infection and in the evaluation of hydronephrosis and megaureter. It permits the detection of ureteropelvic junction obstruction through the study of the filling and emptying of the pyelocalyceal system and ureter.

In conclusion, results of the present study validated the dynamic US technique as a sensitive diagnostic method to aid in the evaluation of bladder dysfunction in children. The analysis of detrusor activity with dynamic US opened a new field for the approach of urinary incontinence in children and adolescents. Dynamic US is also useful in the control of clean intermittent catheterization, the use of anticholinergics, and the therapy of pelvic-floor muscles.

	ACKNOWLEDGMENTS

 
We extend grateful thanks to M. A. Vasconcelos, MD, and V. P. Marino, MD, for their generous help and contributions to the present study.

	FOOTNOTES

 
Abbreviation: MCC = maximum cystometric capacity

Author contributions: Guarantors of integrity of entire study, E.M.L., M.F.T.F.F.; study concepts, M.F.T.F.F.; study design, E.M.L., M.F.T.F.F.; literature research, M.F.T.F.F.; clinical studies, E.M.L., M.F.T.F.F.; data acquisition, A.C.M., C.R.P., M.F.T.F.F.; data analysis/interpretation, T.M.S., E.M.A.G.; statistical analysis, T.M.S., E.M.A.G.; manuscript preparation, M.F.T.F.F.; manuscript definition of intellectual content, E.M.L., M.F.T.F.F.; manuscript editing, M.F.T.F.F.; manuscript revision/review and final version approval, E.M.L., M.F.T.F.F.

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This Article Abstract Figures Only Full Text (PDF) All Versions of this Article: 2272011872v1 227/2/340    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Filgueiras, M. F. T. F. Articles by Pires, C. R. Search for Related Content PubMed PubMed Citation Articles by Filgueiras, M. F. T. F. Articles by Pires, C. R.