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Urethral ratio on voiding cystourethrogram: A comparative method to assess success of posterior urethral valve ablation
Journal of Pediatric Urology (2010) 6, 32e36
Urethral ratio on voiding cystourethrogram: A comparative method to assess success of posterior urethral valve ablation Rahul K. Gupta*, Hemanshi S. Shah, Vinay Jadhav, Abhaya Gupta, Advait Prakash, Bejal Sanghvi, Sandesh V. Parelkar Department of Pediatric Surgery, Seth G.S.M.C. & King Edward Memorial Hospital, Mumbai, Maharashtra, India Received 15 March 2009; accepted 19 May 2009 Available online 26 June 2009
KEYWORDS Posterior urethral valves (PUV); Voiding cystourethrogram (VCUG); Urethral ratio
Abstract Objective: To develop a simple, objective and reproducible quantitative measurement to assess success of posterior urethral valve ablation. Method: In 30 patients with posterior urethral valves the diagnosis was confirmed by voiding cystourethrogram (VCUG). Our protocol was to perform valve ablation, and repeat VCUG at 12 weeks postoperatively. Urethral ratio was calculated by dividing the posterior urethral diameter by the anterior urethral diameter. Thirty males undergoing VCUG for urinary tract infections were evaluated as normative controls. Results: Median age of controls was 12 months (2 dayse6 years) and of study group was 13 months (1 daye11 years). Mean urethral ratio in pre-fulguration group was 4.94 (2.97) and in post-fulguration group was 2.134 (1.19) (P < 0.001). The mean urethral ratio in the control group of 1.73 (0.577) was significantly different from the pre-fulguration group result (P < 0.001), but not significantly different in comparison to the post-fulguration group (P Z 0.104). Conclusion: Calculation of urethral ratio on VCUG as a method of assessment of outcome of fulguration is objective, reproducible, and allows preoperative and postoperative VCUG from different facilities to be compared. A post-fulguration urethral ratio of 2.5e3 represents an acceptable result postoperatively. ª 2009 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
Introduction
* Corresponding author. E-mail address: [email protected] (R.K. Gupta).
PUV are one of the commonest causes of obstructive uropathy in infancy and childhood, and are surgically correctable. Since Young and associates classified PUV in 1919 the condition has been reported widely, but the
1477-5131/$36 ª 2009 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jpurol.2009.05.009
Urethral ratio for assessment of posterior urethral valve ablation problems of preliminary treatment and method to assess success of fulguration remain unsolved. Valve ablation is considered the best primary treatment. However, technical methods to assess the success of this therapy are still wanting. There are no data available in the literature to compare outcome (adequacy of valve ablation) in patients with PUV fulgurated by different groups of surgeons. Some authors recommend follow-up VCUG, some use of a uroflowmeter, while others recommend follow-up cystoscopy. With these methods, postoperative assessment is based on qualitative factors and clinical judgment; no quantitative guidelines have been formulated. In the present study, we tried to develop a simple, objective and quantitative measurement to assess the success of valve ablation.
Material and methods A total of 30 cases of PUV were diagnosed and managed in our department, between August 2005 and October 2007. Identification and demographic information was collected prospectively. Patient age at diagnosis ranged between 1 day and 11 years; 14 were younger than 1 year. In a minority of cases VCUG was performed elsewhere. Basic renal function tests, including blood urea nitrogen, serum creatinine, venous blood gas analysis, serum electrolytes, as well as urinary ultrasonography, were performed, both before fulguration and at 8 weeks postfulguration. Post-micturition residual volume measurement and uroflowmetry were not part of the protocol when we started the prospective study. The diagnosis was confirmed by VCUG. Our protocol was to perform valve ablation and then to repeat the VCUG at 12 weeks postoperatively. In each case a urethral catheter was kept in for 48 h postfulguration. We performed cystoscopy at 12 weeks (just after VCUG) to check for any residual valves, so as to correlate completion of fulguration with normalization of urethral ratio on repeat VCUG. Depending on the clinical progress and VCUG appearance, and presence of valves on check cystoscopy, repeat ablation was performed. We used a #10 cystoscope with resectoscope and a cutting diathermy current. When the urethra was too small for this instrument, a #7.5 cystoscope with bugbee electrode was used for fulguration. In all cases, VCUG images were stored in the department picture-archiving system so that pre- and post-operative images were available for review. A high osmolar contrast media at approximately 150 mg/ml is perfectly adequate for pediatric VCUG examinations. At our institute, we used a mixture of sodium and meglumine amidotrizoate (urograffin 76%). Before instillation, contrast media was warmed to body temperature. We defined urethral ratio as the diameter of the posterior urethra divided by the diameter of the anterior urethra, measured during the voiding phase, on an oblique film. The diameter of the posterior urethra was measured transversely at a point halfway between the bladder neck and the distal end of the membranous urethra. The diameter of the anterior urethra was taken as the transverse diameter at the point of maximum distension in the bulbar urethra. We aimed to measure these diameters on a voiding
33
film without a catheter. Both measurements were taken on the same film. When several films were available, measurements were made on the image where the anterior urethra was the most distended. Urethral ratio was calculated on VCUG (Table 1), both before (Fig. 1) and after (Fig. 2) fulguration. As a control, the same urethral ratio was calculated for 30 male children (Fig. 3), who had a normal VCUG as part of their evaluation for suspected urinary tract pathology, to be representative of adequate valve ablation and relief of obstruction.
Results Of the 30 patients in the study group, nine who were diagnosed antenatally were asymptomatic but the others had urinary symptoms. The diagnosis of PUV was suspected on VCUG and confirmed on cystoscopy. Patient age at diagnosis ranged between 1 day and 11 years. In the study group, 14 were younger than 1 year. Nine patients presented following antenatal diagnosis and five presented after a UTI. In all patients, check cystoscopy was done at 12 weeks after last fulguration. Two patients (case nos 4 and 17, with
Table 1 Comparison of urethral ratios between pre-fulguration and post-fulguration groups. Case no. Age of patient Pre-fulguration Post-fulguration urethral ratio urethral ratio 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
13 months 1 day 18 months 9 months 4 months 10 months 4 years 11 years 13 months 2 months 2 years 6 months 2.6 years 7 months 1 month 16 mths 19 months 3 months 11 months 2.2 years 2.9 years 5 months 13 months 4.5 years 4 months 15 months 3.3 years 13 months 8 months 9 months
2.5 8 8 8.5 1.4 4.5 1.75 2 5 2 2.3 1.4 2.5 3.5 6 4 7 2 1.75 5 8 3 9 12 6.5 6 11 4 6 5
1.8 2 1 6 1 1.66 1 2 1.25 1.6 1.2 1.2 1 1.25 3 2.6 5 2 1.6 3.3 2.2 2 1.66 1.5 3.5 2.3 2 2.5 1.5 2
34
Figure 1 Pre-fulguration diameter of posterior and anterior urethra on VCUG.
R.K. Gupta et al. For comparison of pre-fulguration and post-fulguration urethral ratios in the study group (n Z 30), the paired t-test was applied. The mean urethral ratio in the pre-fulguration group was 4.94 (2.97) and in the post-fulguration group was 2.134 (1.19). The difference between these two values is highly significant (P < 0.001). For comparison of urethral ratios between the control group (n Z 30) and study group (n Z 30), the unpaired ttest was applied. The mean urethral ratio in the control group was 1.73 (0.577). This is highly significantly different compared to the pre-fulguration group (P < 0.001), but not significantly different compared to the post-fulguration group (P Z 0.104, i.e. P > 0.05). A ratio of 2.5e3 represented an acceptable result postoperatively. In the control group, 29 of 30 had a urethral ratio less than 3, and only five patients with PUV had a urethral ratio of more than or equal to 3 after we had completed what we considered a successful ablation.
Discussion pre-fulguration urethral ratio of 8 and 7 and post-fulguration ratio of 6 and 5, respectively) were found to have residual valves and underwent repeat fulguration. A persistently high urethral ratio could be explained by the presence of residual valves evident on the follow-up check cystoscopy. Median urethral ratio in the control group was 1.5 (range 1e2.5). Median urethral ratio in the study group was 4.7 (range 1.4e12) before fulguration and 2 (range 1e6) after fulguration.
Figure 2 Post-fulguration diameter of posterior and anterior urethra on VCUG.
Management and assessment of outcome of treatment in patients with PUV have undergone a great deal of change since the condition was first described. The concern in such patients is not only the efficient fulguration of the valves but also the management of sequelae and assessment of adequacy of fulguration. The present study consists of 30 cases of PUV treated in the pediatric surgical unit of a tertiary teaching hospital in the city of Mumbai. The significance of reduction of posterior urethral diameter post-fulguration, as assessed by calculation of urethral ratio on VCUG, was analyzed. Shopfner and Hutch studied the normal urethra on VCUG and described its radiological and anatomical features [1]. Popek et al. analyzed the histological and pathological changes in the urethra with development and with obstruction [2]. Both groups hypothesized that the posterior urethra has the capacity to stretch with increased voiding pressure due to its unique histological and anatomical configuration, in contrast to the anterior urethral segment. There is variability of urethral
Figure 3 Control diameter of posterior and anterior urethra on VCUG.
Urethral ratio for assessment of posterior urethral valve ablation measurement depending on the stage of voiding, voiding volume and position of patient. Ideally, voiding films on VCUG should be obtained without a catheter in the urethra. But sometimes patients do not void without a catheter, and a film showing the urethra with a catheter in place is better than no film at all. An indwelling catheter will tend to decrease the urethral ratio by decompressing the posterior urethra and opening the anterior urethra [3]. Endoscopic valve ablation is the preferred treatment for PUV. The aim of the procedure is to relieve infravesical obstruction. Duckett and Snow observed that approximately 20e30% of patients require a second ablation to achieve satisfactory valve ablation [3]. They stated that it is preferable to under fulgurate than over fulgurate, to avoid the risk of urethral stricture or incontinence. Our incidence of repeat valve ablation was 6% which is less than that of Duckett and Snow. Some authors recommend routine cystoscopic follow-up after valve ablation, allowing assessment of the valve ablation and further therapy, if needed [4]. However, this has the disadvantages of being more expensive and invasive than repeat VCUG, and requires repeat anesthesia. Most authors accept that repeat VCUG at 6e8 weeks after valve ablation is the best method of assessing surgical outcome [5]. We repeated VCUG 8e12 weeks post-fulguration. We have demonstrated that urethral ratio can be measured, and that a decrease in this ratio appears to correlate with our clinical assessment of a satisfactory valve ablation, as out of 30 patients only two had residual valves on check cystoscopy at 12 weeks after fulguration. Uroflowmetry can serve as a non-invasive screening test for selecting patients who should undergo more sophisticated urodynamic studies. Uroflowmetry measures urine voided per unit time, which is usually expressed as milliliters per second. The International Children’s Continence Society (ICCS) has standardized certain objective measurements to be recorded during uroflow measurement [6]. These include flow pattern, voided volume, maximum flow rate (Qmax), voiding time, and time to maximum flow. However, flow pattern, Qmax, and volume voided generally are regarded to be the most clinically useful for both screening and following patients. The Qmax is helpful in distinguishing those who have bladder outlet obstruction from those who do not. Sharp peaks in the flow curve are usually artefacts, and so maximum flow should be documented only at a peak level with duration of at least 2 s. In studies of normal children and adults, a linear correlation has been found between maximum flow and the square root of voided volume. Thus, preliminary evaluation of the results of a flow measurement is possible. If the square of the maximum flow ([ml per second]2) is equal to or exceeds voided volume in milliliters, the recorded maximum flow is most probably within the normal range. The precise shape of the flow curve is determined by detrusor contractility, any abdominal straining. In normal voiding the curve is smooth and bell-shaped. Overactive bladder may produce an explosive voiding contraction that appears in the flow measurement as a high amplitude curve of short duration, i.e. a tower-shaped curve. A child with organic outlet tract obstruction often has a low amplitude and rather even flow curve, i.e. a plateau-shaped curve.
35
Similarly, this may be the case when there is a tonic sphincter contraction during voiding. However, more commonly, sphincter overactivity during voiding is seen as sharp peaks and troughs, producing an irregular or staccato flow curve. This is labelled as a continuous but fluctuating flow curve. To qualify for the staccato label the fluctuations should be larger than the square root of the maximum flow rate. Finally, in the case of an underactive or acontractile detrusor when contraction of the abdominal muscles creates the main force for bladder evacuation, the flow curve usually shows discrete peaks corresponding to each strain, separated by segments with zero flow; namely, an interrupted or fractionated flow curve. To avoid confusion due to a multitude of terms regarding the shape of the flow curve the ICCS suggests that a certain terminology should be adopted, including bell, tower, plateau, staccato and interrupted. These appellations are not a guarantee to the underlying diagnostic abnormality, but rather they should serve as a guide to the existence of a specific condition [7]. The strength of uroflow is in helping to identify patients who need further urodynamic studies to diagnose an underlying problem. We did not use uroflowmetry as it was not part of the protocol when we started the prospective study. It could be argued that a better assessment of PUV ablation could be made with preoperative and postoperative urodynamic studies. To perform urodynamic studies in infants, it is necessary to insert a suprapubic catheter to avoid interfering with urethral resistance during voiding. This procedure is far too invasive in infants who are often unwell and have impaired renal function. Bani Hani et al. [8] in their study of 23 patients with PUV suggested a post-fulguration urethral ratio of 3.5 as an acceptable measure to assess completeness of ablation. In their study, mean urethral ratio was 2.6 in 31 normal males undergoing VCUG for investigation for UTI. In our study, we found that a post-fulguration urethral ratio of 2.5e3 represented an acceptable result postoperatively. Further studies will be needed to adjust the urethral ratio considered acceptable after treatment, and to confirm these findings.
Conclusions Urethral ratio on VCUG is a simple measurement that allows quantitative assessment of valve ablation. A post-fulguration urethral ratio of 2.5e3 represents an acceptable result postoperatively. The calculation of urethral ratio on VCUG is an objective method of assessment of outcome of fulguration, is reproducible, and allows preoperative and postoperative VCUG from different facilities to be compared.
Conflict of interest None.
Funding None.
36
Ethical statement Approves by institutional board and review committee.
References [1] Shopfner CE, Hutch JA. The normal urethrogram. Radiol Clin North Am 1968;6:165. [2] Popek EJ, Tyson RW, Miller GJ, Caldwell SA. Prostate development in prune belly syndrome and posterior urethral valves: etiology of prune belly syndrome e lower urinary tract obstruction or primary mesenchymal defect? Pediatr Pathol 1991;111:1. [3]. Duckett JW, Snow BW. Disorders of urethra and penis. In: Campbell MF, Walsh PC, editors. Campbell’s urology. 5th ed. Philadelphia: W.B. Saunders Co.; 1986. p. 2000e30.
R.K. Gupta et al. [4] Imaji R, Dewan PA. The clinical and radiological findings in boys with endoscopically severe congenital posterior urethral obstruction. BJU Int 2001;88:263. [5]. Edmond T, Gonazales J. Posterior urethral valves and other urethral anomalies. In: Walsh PC, Gittes RF, Perlmutter AD, Stamey TA, editors. Campbell’s urology. 6th ed. Philadelphia: W.B. Saunders Co.; 1992. p. 1872e92. [6] Griffiths D, Hofner K, van Mastrigt R. Standardization of terminology of lower urinary tract function: pressure-flow studies of voiding, urethral resistance, and urethral obstruction. Neurourol Urodyn 1997;16:1e18. [7] Neve ´us T, Gontard VA, Hoebeke P. The standardization of terminology of lower urinary tract function in children and adolescents: report from the Standardisation Committee of the International Children’s Continence Society. J Urol 2006;176:314e24. [8] Bani Hani O, Prelog K, Smith GH. A method to assess posterior urethral valve ablation. J Urol 2006;176:303e5.
Urethral ratio on voiding cystourethrogram: A comparative method to assess success of posterior urethral valve ablation Rahul K. Gupta*, Hemanshi S. Shah, Vinay Jadhav, Abhaya Gupta, Advait Prakash, Bejal Sanghvi, Sandesh V. Parelkar Department of Pediatric Surgery, Seth G.S.M.C. & King Edward Memorial Hospital, Mumbai, Maharashtra, India Received 15 March 2009; accepted 19 May 2009 Available online 26 June 2009
KEYWORDS Posterior urethral valves (PUV); Voiding cystourethrogram (VCUG); Urethral ratio
Abstract Objective: To develop a simple, objective and reproducible quantitative measurement to assess success of posterior urethral valve ablation. Method: In 30 patients with posterior urethral valves the diagnosis was confirmed by voiding cystourethrogram (VCUG). Our protocol was to perform valve ablation, and repeat VCUG at 12 weeks postoperatively. Urethral ratio was calculated by dividing the posterior urethral diameter by the anterior urethral diameter. Thirty males undergoing VCUG for urinary tract infections were evaluated as normative controls. Results: Median age of controls was 12 months (2 dayse6 years) and of study group was 13 months (1 daye11 years). Mean urethral ratio in pre-fulguration group was 4.94 (2.97) and in post-fulguration group was 2.134 (1.19) (P < 0.001). The mean urethral ratio in the control group of 1.73 (0.577) was significantly different from the pre-fulguration group result (P < 0.001), but not significantly different in comparison to the post-fulguration group (P Z 0.104). Conclusion: Calculation of urethral ratio on VCUG as a method of assessment of outcome of fulguration is objective, reproducible, and allows preoperative and postoperative VCUG from different facilities to be compared. A post-fulguration urethral ratio of 2.5e3 represents an acceptable result postoperatively. ª 2009 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.
Introduction
* Corresponding author. E-mail address: [email protected] (R.K. Gupta).
PUV are one of the commonest causes of obstructive uropathy in infancy and childhood, and are surgically correctable. Since Young and associates classified PUV in 1919 the condition has been reported widely, but the
1477-5131/$36 ª 2009 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jpurol.2009.05.009
Urethral ratio for assessment of posterior urethral valve ablation problems of preliminary treatment and method to assess success of fulguration remain unsolved. Valve ablation is considered the best primary treatment. However, technical methods to assess the success of this therapy are still wanting. There are no data available in the literature to compare outcome (adequacy of valve ablation) in patients with PUV fulgurated by different groups of surgeons. Some authors recommend follow-up VCUG, some use of a uroflowmeter, while others recommend follow-up cystoscopy. With these methods, postoperative assessment is based on qualitative factors and clinical judgment; no quantitative guidelines have been formulated. In the present study, we tried to develop a simple, objective and quantitative measurement to assess the success of valve ablation.
Material and methods A total of 30 cases of PUV were diagnosed and managed in our department, between August 2005 and October 2007. Identification and demographic information was collected prospectively. Patient age at diagnosis ranged between 1 day and 11 years; 14 were younger than 1 year. In a minority of cases VCUG was performed elsewhere. Basic renal function tests, including blood urea nitrogen, serum creatinine, venous blood gas analysis, serum electrolytes, as well as urinary ultrasonography, were performed, both before fulguration and at 8 weeks postfulguration. Post-micturition residual volume measurement and uroflowmetry were not part of the protocol when we started the prospective study. The diagnosis was confirmed by VCUG. Our protocol was to perform valve ablation and then to repeat the VCUG at 12 weeks postoperatively. In each case a urethral catheter was kept in for 48 h postfulguration. We performed cystoscopy at 12 weeks (just after VCUG) to check for any residual valves, so as to correlate completion of fulguration with normalization of urethral ratio on repeat VCUG. Depending on the clinical progress and VCUG appearance, and presence of valves on check cystoscopy, repeat ablation was performed. We used a #10 cystoscope with resectoscope and a cutting diathermy current. When the urethra was too small for this instrument, a #7.5 cystoscope with bugbee electrode was used for fulguration. In all cases, VCUG images were stored in the department picture-archiving system so that pre- and post-operative images were available for review. A high osmolar contrast media at approximately 150 mg/ml is perfectly adequate for pediatric VCUG examinations. At our institute, we used a mixture of sodium and meglumine amidotrizoate (urograffin 76%). Before instillation, contrast media was warmed to body temperature. We defined urethral ratio as the diameter of the posterior urethra divided by the diameter of the anterior urethra, measured during the voiding phase, on an oblique film. The diameter of the posterior urethra was measured transversely at a point halfway between the bladder neck and the distal end of the membranous urethra. The diameter of the anterior urethra was taken as the transverse diameter at the point of maximum distension in the bulbar urethra. We aimed to measure these diameters on a voiding
33
film without a catheter. Both measurements were taken on the same film. When several films were available, measurements were made on the image where the anterior urethra was the most distended. Urethral ratio was calculated on VCUG (Table 1), both before (Fig. 1) and after (Fig. 2) fulguration. As a control, the same urethral ratio was calculated for 30 male children (Fig. 3), who had a normal VCUG as part of their evaluation for suspected urinary tract pathology, to be representative of adequate valve ablation and relief of obstruction.
Results Of the 30 patients in the study group, nine who were diagnosed antenatally were asymptomatic but the others had urinary symptoms. The diagnosis of PUV was suspected on VCUG and confirmed on cystoscopy. Patient age at diagnosis ranged between 1 day and 11 years. In the study group, 14 were younger than 1 year. Nine patients presented following antenatal diagnosis and five presented after a UTI. In all patients, check cystoscopy was done at 12 weeks after last fulguration. Two patients (case nos 4 and 17, with
Table 1 Comparison of urethral ratios between pre-fulguration and post-fulguration groups. Case no. Age of patient Pre-fulguration Post-fulguration urethral ratio urethral ratio 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
13 months 1 day 18 months 9 months 4 months 10 months 4 years 11 years 13 months 2 months 2 years 6 months 2.6 years 7 months 1 month 16 mths 19 months 3 months 11 months 2.2 years 2.9 years 5 months 13 months 4.5 years 4 months 15 months 3.3 years 13 months 8 months 9 months
2.5 8 8 8.5 1.4 4.5 1.75 2 5 2 2.3 1.4 2.5 3.5 6 4 7 2 1.75 5 8 3 9 12 6.5 6 11 4 6 5
1.8 2 1 6 1 1.66 1 2 1.25 1.6 1.2 1.2 1 1.25 3 2.6 5 2 1.6 3.3 2.2 2 1.66 1.5 3.5 2.3 2 2.5 1.5 2
34
Figure 1 Pre-fulguration diameter of posterior and anterior urethra on VCUG.
R.K. Gupta et al. For comparison of pre-fulguration and post-fulguration urethral ratios in the study group (n Z 30), the paired t-test was applied. The mean urethral ratio in the pre-fulguration group was 4.94 (2.97) and in the post-fulguration group was 2.134 (1.19). The difference between these two values is highly significant (P < 0.001). For comparison of urethral ratios between the control group (n Z 30) and study group (n Z 30), the unpaired ttest was applied. The mean urethral ratio in the control group was 1.73 (0.577). This is highly significantly different compared to the pre-fulguration group (P < 0.001), but not significantly different compared to the post-fulguration group (P Z 0.104, i.e. P > 0.05). A ratio of 2.5e3 represented an acceptable result postoperatively. In the control group, 29 of 30 had a urethral ratio less than 3, and only five patients with PUV had a urethral ratio of more than or equal to 3 after we had completed what we considered a successful ablation.
Discussion pre-fulguration urethral ratio of 8 and 7 and post-fulguration ratio of 6 and 5, respectively) were found to have residual valves and underwent repeat fulguration. A persistently high urethral ratio could be explained by the presence of residual valves evident on the follow-up check cystoscopy. Median urethral ratio in the control group was 1.5 (range 1e2.5). Median urethral ratio in the study group was 4.7 (range 1.4e12) before fulguration and 2 (range 1e6) after fulguration.
Figure 2 Post-fulguration diameter of posterior and anterior urethra on VCUG.
Management and assessment of outcome of treatment in patients with PUV have undergone a great deal of change since the condition was first described. The concern in such patients is not only the efficient fulguration of the valves but also the management of sequelae and assessment of adequacy of fulguration. The present study consists of 30 cases of PUV treated in the pediatric surgical unit of a tertiary teaching hospital in the city of Mumbai. The significance of reduction of posterior urethral diameter post-fulguration, as assessed by calculation of urethral ratio on VCUG, was analyzed. Shopfner and Hutch studied the normal urethra on VCUG and described its radiological and anatomical features [1]. Popek et al. analyzed the histological and pathological changes in the urethra with development and with obstruction [2]. Both groups hypothesized that the posterior urethra has the capacity to stretch with increased voiding pressure due to its unique histological and anatomical configuration, in contrast to the anterior urethral segment. There is variability of urethral
Figure 3 Control diameter of posterior and anterior urethra on VCUG.
Urethral ratio for assessment of posterior urethral valve ablation measurement depending on the stage of voiding, voiding volume and position of patient. Ideally, voiding films on VCUG should be obtained without a catheter in the urethra. But sometimes patients do not void without a catheter, and a film showing the urethra with a catheter in place is better than no film at all. An indwelling catheter will tend to decrease the urethral ratio by decompressing the posterior urethra and opening the anterior urethra [3]. Endoscopic valve ablation is the preferred treatment for PUV. The aim of the procedure is to relieve infravesical obstruction. Duckett and Snow observed that approximately 20e30% of patients require a second ablation to achieve satisfactory valve ablation [3]. They stated that it is preferable to under fulgurate than over fulgurate, to avoid the risk of urethral stricture or incontinence. Our incidence of repeat valve ablation was 6% which is less than that of Duckett and Snow. Some authors recommend routine cystoscopic follow-up after valve ablation, allowing assessment of the valve ablation and further therapy, if needed [4]. However, this has the disadvantages of being more expensive and invasive than repeat VCUG, and requires repeat anesthesia. Most authors accept that repeat VCUG at 6e8 weeks after valve ablation is the best method of assessing surgical outcome [5]. We repeated VCUG 8e12 weeks post-fulguration. We have demonstrated that urethral ratio can be measured, and that a decrease in this ratio appears to correlate with our clinical assessment of a satisfactory valve ablation, as out of 30 patients only two had residual valves on check cystoscopy at 12 weeks after fulguration. Uroflowmetry can serve as a non-invasive screening test for selecting patients who should undergo more sophisticated urodynamic studies. Uroflowmetry measures urine voided per unit time, which is usually expressed as milliliters per second. The International Children’s Continence Society (ICCS) has standardized certain objective measurements to be recorded during uroflow measurement [6]. These include flow pattern, voided volume, maximum flow rate (Qmax), voiding time, and time to maximum flow. However, flow pattern, Qmax, and volume voided generally are regarded to be the most clinically useful for both screening and following patients. The Qmax is helpful in distinguishing those who have bladder outlet obstruction from those who do not. Sharp peaks in the flow curve are usually artefacts, and so maximum flow should be documented only at a peak level with duration of at least 2 s. In studies of normal children and adults, a linear correlation has been found between maximum flow and the square root of voided volume. Thus, preliminary evaluation of the results of a flow measurement is possible. If the square of the maximum flow ([ml per second]2) is equal to or exceeds voided volume in milliliters, the recorded maximum flow is most probably within the normal range. The precise shape of the flow curve is determined by detrusor contractility, any abdominal straining. In normal voiding the curve is smooth and bell-shaped. Overactive bladder may produce an explosive voiding contraction that appears in the flow measurement as a high amplitude curve of short duration, i.e. a tower-shaped curve. A child with organic outlet tract obstruction often has a low amplitude and rather even flow curve, i.e. a plateau-shaped curve.
35
Similarly, this may be the case when there is a tonic sphincter contraction during voiding. However, more commonly, sphincter overactivity during voiding is seen as sharp peaks and troughs, producing an irregular or staccato flow curve. This is labelled as a continuous but fluctuating flow curve. To qualify for the staccato label the fluctuations should be larger than the square root of the maximum flow rate. Finally, in the case of an underactive or acontractile detrusor when contraction of the abdominal muscles creates the main force for bladder evacuation, the flow curve usually shows discrete peaks corresponding to each strain, separated by segments with zero flow; namely, an interrupted or fractionated flow curve. To avoid confusion due to a multitude of terms regarding the shape of the flow curve the ICCS suggests that a certain terminology should be adopted, including bell, tower, plateau, staccato and interrupted. These appellations are not a guarantee to the underlying diagnostic abnormality, but rather they should serve as a guide to the existence of a specific condition [7]. The strength of uroflow is in helping to identify patients who need further urodynamic studies to diagnose an underlying problem. We did not use uroflowmetry as it was not part of the protocol when we started the prospective study. It could be argued that a better assessment of PUV ablation could be made with preoperative and postoperative urodynamic studies. To perform urodynamic studies in infants, it is necessary to insert a suprapubic catheter to avoid interfering with urethral resistance during voiding. This procedure is far too invasive in infants who are often unwell and have impaired renal function. Bani Hani et al. [8] in their study of 23 patients with PUV suggested a post-fulguration urethral ratio of 3.5 as an acceptable measure to assess completeness of ablation. In their study, mean urethral ratio was 2.6 in 31 normal males undergoing VCUG for investigation for UTI. In our study, we found that a post-fulguration urethral ratio of 2.5e3 represented an acceptable result postoperatively. Further studies will be needed to adjust the urethral ratio considered acceptable after treatment, and to confirm these findings.
Conclusions Urethral ratio on VCUG is a simple measurement that allows quantitative assessment of valve ablation. A post-fulguration urethral ratio of 2.5e3 represents an acceptable result postoperatively. The calculation of urethral ratio on VCUG is an objective method of assessment of outcome of fulguration, is reproducible, and allows preoperative and postoperative VCUG from different facilities to be compared.
Conflict of interest None.
Funding None.
36
Ethical statement Approves by institutional board and review committee.
References [1] Shopfner CE, Hutch JA. The normal urethrogram. Radiol Clin North Am 1968;6:165. [2] Popek EJ, Tyson RW, Miller GJ, Caldwell SA. Prostate development in prune belly syndrome and posterior urethral valves: etiology of prune belly syndrome e lower urinary tract obstruction or primary mesenchymal defect? Pediatr Pathol 1991;111:1. [3]. Duckett JW, Snow BW. Disorders of urethra and penis. In: Campbell MF, Walsh PC, editors. Campbell’s urology. 5th ed. Philadelphia: W.B. Saunders Co.; 1986. p. 2000e30.
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