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Table of Contents   
ORIGINAL ARTICLE
Year : 2022  |  Volume : 27  |  Issue : 1  |  Page : 53-59
 

Correlation of urethral ratio and bladder wall thickness with cystoscopic findings in posterior urethral valve patients to assess residual valves


1 Department of Pediatric Surgery, All India Institute of Medical Sciences, Jodhpur, Rajasthan, India
2 Department of Pediatric Surgery, Chacha Nehru Bal Chikitsalaya, New Delhi, India
3 Department of Diagnostic and Interventional Radiology, All India Institute of Medical Sciences, Jodhpur, Rajasthan, India

Date of Submission18-Sep-2020
Date of Decision04-Feb-2021
Date of Acceptance23-May-2021
Date of Web Publication11-Jan-2022

Correspondence Address:
Dr. Kirtikumar J Rathod
Department of Pediatric Surgery, All India Institute of Medicals Sciences, Jodhpur, Rajasthan
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiaps.JIAPS_318_20

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   Abstract 


Introduction: Posterior urethral valve (PUV) is life threatening congenital anomaly of urinary tract. Aim of the study was to correlate urethral ratio (UR) and bladder wall thickness (BWT) with cystoscopic findings in PUV patients to assess residual valves and to validate UR as a diagnostic tool for residual valves. It also aimed to assess the utility of bladder wall thickness in diagnosis of residual valves.
Materials and Methods: A total of 31 patients were included in the prospective study done from 2017 to 2019. Calculation of UR was done in oblique VCUG films by dividing maximum posterior and anterior urethral diameter without the catheter insitu. Measurement of BWT was done at dome and bladder neck at full distension with feeding tube insitu and was done at same volume in follow up. The procedure was repeated at 3 months follow up. The findings were compared with cystoscopic findings for the status of residual valves as gold standard. Each patient served as control for self in the study.
Results: Median age of presentation was 1 years with range of 1day to 10 years. The most common complains at the time of presentation in our study was straining (35.48%) followed by antenatally diagnosed patients (25.81%) and recurrent UTI (19.36%). Pre fulguration median UR was 2.45. Post Fulguration median UR was 1.20. It showed a statistically significant reduction (p < 0.001) after fulguration. Pre fulguration median BWT was 4 mm. Post fulguration median BWT was 2.5 mm. BWT showed a statistically significant reduction (p < 0.001) after fulguration as well. ROC curve was plotted for UR and BWT. BWT more than 1.95 mm (sensitivity-80%) and UR more than 1.2 (sensitivity-70%) indicates residual valves.
Conclusion: A step ladder approach including BWT, UR and check cystoscopy can serve as a new diagnostic algorithm for the assessment of residual valves thereby avoiding extra radiation and general anesthesia exposure.


Keywords: Bladder wall thickness, congenital posterior urethral valves, cystoscopy, urethral ratio


How to cite this article:
Motiwala T, Sinha A, Rathod KJ, Manchanda V, Yadav T, Jadhav A, Pathak M, Saxena R. Correlation of urethral ratio and bladder wall thickness with cystoscopic findings in posterior urethral valve patients to assess residual valves. J Indian Assoc Pediatr Surg 2022;27:53-9

How to cite this URL:
Motiwala T, Sinha A, Rathod KJ, Manchanda V, Yadav T, Jadhav A, Pathak M, Saxena R. Correlation of urethral ratio and bladder wall thickness with cystoscopic findings in posterior urethral valve patients to assess residual valves. J Indian Assoc Pediatr Surg [serial online] 2022 [cited 2022 Aug 8];27:53-9. Available from: https://www.jiaps.com/text.asp?2022/27/1/53/335571





   Introduction Top


Posterior urethral valve (PUV) is life-threatening congenital anomaly of urinary tract occurring in 1 in 8000 live births.[1] If not treated in time, it results in renal insufficiency in up to 50% of patients.[2] In many children with PUV, there is bladder outlet obstruction that leads to impaired renal function secondary to renal dysplasia.[3] Most authors believe that valve ablation is the best primary treatment.[4],[5],[6] Although the initial treatment of PUVs is a relatively simple and reproducible procedure with adequate training, the bladder outlet obstruction during the early fetal development creates downstream consequences that afflict an individual, often for a lifetime. It is a common saying that the actual management of PUV begins after fulguration of valves. The patients are usually followed up at 8–12 weeks after fulguration of valves. The presence of residual valves may have serious long-term implications if not detected and managed timely. Many surgeons go for repeat cystoscopy to see residual valves while others repeat Voiding Cystourethrogram (VCUG) to measure posterior to anterior urethral ratio for obstruction.[7],[8] However, there is no sufficient evidence to see the sensitivity and specificity of cutoff values of urethral ratio that is to be used for screening.

PUV leads to the obstruction of urine flow which increases bladder pressure which causes increase in the thickness of the bladder wall. Bladder wall hypertrophy is a sequelae of bladder outlet obstruction, and hence, it is very logical to consider it as an indicator to assess bladder outlet obstruction.[9] If there is no methodological discrepancy, bladder wall thickness and detrusor wall thickness (DWT) can be used effectively as a noninvasive test for assessing lower urinary tract conditions.[10] Close et al. demonstrated the resolution of bladder wall thickness after valve ablation in PUV patients.[11] Therefore, in patients with residual valves, it is less likely to resolve. To the best of our knowledge, there is no evidence in the literature for the use of bladder thickness on sonography as a tool to evaluate residual valves in patients who have undergone valve fulguration. In this study, we attempt to see the aptness of urethral ratio and bladder thickness as a method to evaluate the residual valves and to find out the values of urethral ratio to be used as a screening test. The aim of the study was to correlate urethral ratio and bladder wall thickness with cystoscopic findings in PUV patients to assess residual valves, to validate urethral ratio as a diagnostic tool for residual valves and to assess the utility of bladder wall thickness in the diagnosis of residual valves.


   Materials and Methods Top


This was a 2-year prospective hospital-based study from December 2017 to December 2019. All the patients <18 years, diagnosed with PUV were included in the study. A total of 31 patients were included in the study period. The patients operated outside, those with associated urethral anomalies such as anterior urethral valves, urethral stricture, and neurogenic bladder were excluded from the study. The study protocol fulfilled the ethical consideration according to the Helsinki declaration and commenced after the approval by the Institutional Ethics Committee. A fixed protocol was followed for the management.

After obtaining proper consent, patients who met the inclusion criteria were enrolled in the study. The selected participant was enquired about the details regarding demographic and socioeconomic characteristics such as patient's age, gender, and presenting complaints. Complete blood count, blood urea, creatinine, urine routine, and culture were sent for each patient. Then, the patients were subjected to VCUG after the urine cultures were sterile. The patients with culture positive urinary tract infections (UTI) were treated based on culture sensitivity, and the procedure was done only when the urine culture was sterile.

The diagnosis was made on the basis of symptoms, VCUG findings, and cystoscopy. Clinical suspicion followed by VCUG films showing characteristic dilatation of urethra or patients with strong clinical suspicion and doubtful VCUG but showing the presence of PUVs in cystoscopy was considered as confirmatory for labeling them as patients. Urethral ratio is defined as the diameter of posterior urethra divided by the diameter of anterior urethra measured during the voiding phase on an oblique film. The diameter of posterior urethra was measured transversely at a point halfway between the bladder neck and distal end of membranous urethra. These diameters were measured on voiding film on VCUG without catheter. The diameter of anterior urethra was measured as transverse diameter at point of maximum distension in bulbar urethra. Both measurements were taken on the same film. The results were documented in terms of the ratio [Figure 1]. Bladder wall thickness was measured sonographically (LOGIQ S8; GE Healthcare) at the dome of bladder and at trigone. The sonography was done by radiologist, and an average of three readings was taken as the final thickness of the bladder wall [Figure 2]. The sonography was done after the bladder is distended. The capacity of the bladder was estimated using Koff formula:[12] Capacity (ml) =7 × weight (kg) for age <2 years and capacity (ml) = (age [in years] +2) × 30 for age more than 2 years. The thickness was taken preoperatively and again at 3 months' follow-up. PUV fulguration was done electively. Cystoscopy was done using Karl Storz® cystoscope 9/11 Fr cystoscope under GA (general anesthesia) and valve fulguration was done using Karl Storz® 9/11 Fr resectoscope. To look for residual valves, another cystoscopy was done at 3 months of follow-up. Test was considered positive if the valves were visible on cystoscopic view and were considered negative if the valves were not visible. All the data were entered in Microsoft Excel and analyzed using the statistics analyzing software (IBM Corp. released 2015. IBM SPSS Statistics for windows, version 23.0. Armonk, NY, USA: IBM Corp.)
Figure 1: Method of calculation of urethral ratio in oblique film

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Figure 2: (a and b) showing calculation of bladder wall thickness in distended bladder

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   Results Top


During the study period, a total of 31 patients were enrolled in the study. Out of which, three patients were previously fulgurated in our institute and 1 patient was lost to follow-up after the first visit. The median age of presentation was 1 year with the range of 1 day–10 years. There were two outliers, 8 years and 10 years, respectively [Figure 3].
Figure 3: Showing age at the time of presentation

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[Figure 4] shows the mode of presentation. Patients who had complaints other than those described in [Figure 4] and found to have PUV on workup are included in incidentally diagnosed. Patients who had antenatal ultrasound findings suggestive of PUV are included in antenatally diagnosed.
Figure 4: Pie chart showing mode of presentation

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Median urea at the time of presentation was 28 mg/dL, range – (6–110) mg/dL and median creatinine at the time of presentation was 0.46 mg/dL, range – (0.09–5.62) mg/dL. Ten (32.3%) patients had a culture-positive UTI at the time of presentation, whereas 21 (67.7%) patients had sterile urine culture at the time of presentation. Prefulguration median UR was 2.45, Q1 to Q3-1.70–3.52, range – (0.54–6.97). Postfulguration urethral ratio was available for 27 patients; median was 1.20, Q1 to Q3 – 1.08–1.53, range – (0.40–2.79). Prefulguration median bladder wall thickness was 4 mm, Q1 to Q3 – (3.0–5.0) mm, range – (1.9–8) mm. Postfulguration bladder wall thickness was available for 27 patients, median was 2.5 mm, Q1 to Q3 – (1.9–3.8) mm, range – (1.2–8) mm. Postfulguration urethral ratio and bladder wall thickness were not available for four patients. Bland Altman analysis was done to analyze agreement between urethral ratio and bladder wall thickness before fulguration. The standard deviation (SD) of the observed parameters was within the limits of agreement of the Bland Altman analysis, indicating a good agreement between the observed parameters [Figure 5].
Figure 5: Bland altman analysis showing agreement between urethral ratio and bladder wall thickness before fulguration

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A comparison was done for urethral ratio and bladder wall thickness prefulguration and postfulguration separately. The Wilcoxon signed-rank test showed that after fulguration the urethral ratio showed a statistically significant change (P = 0.000034). A Wilcoxon signed-rank test showed that after fulguration the bladder wall thickness also showed a statistically significant change (P = 0.000173). On check cystoscopy, a total of 16 (51.6%) patients had residual valves and 11 patients (35.5%) had no residual valves. Receiver operator curve (ROC) was plotted for bladder wall thickness [Figure 6]. Area under the curve was 0.72, with a 95% confidence interval (CI) −0.52–0.92. The outlier of 8 mm bladder wall thickness was not considered while plotting the ROC curve. Bladder wall thickness of 1.95 mm has got a sensitivity of 80% and specificity of 45.5% as per the ROC curve. Similarly, ROC curve was plotted for UR [Figure 7]. Area under the curve was 0.87, with a 95% CI − 0.73–1.0. Urethral ratio of 1.20 has got a sensitivity of 87.5% and specificity of 54.5% as per the ROC curve.
Figure 6: Receiver operator curve for bladder wall thickness

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Figure 7: Receiver operator curve for urethral ratio

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A Wilcoxon signed-rank test showed that after fulguration the urethral ratio showed a statistically significant change (Z = −4.14, P = 0.000034). A comparison of ranks table showed a decrease in urethral ratio in 26 patients and one patient having higher urethral ratio after fulguration than before fulguration.


   Discussion Top


PUV management remains to be elusive in spite of the wide spectrum of modalities available in the modern era. The concern varies from efficient fulguration of valves to assessing the adequacy of fulguration of valves. The most preferred mode of the management of PUV patients is endoscopic ablation of valves and it is shown to have better results as compared to diversion procedures.[11] Duckett and Snow in their study concluded that 20%–30% of patients needs second ablation to achieve adequate fulguration of valves.[13] They also stated that it is always better to under fulgurate than to over fulgurate to minimize the risk of stricture. Although not routinely done by all, a repeat micturating cystourethrogram (MCUG) should be performed 3 months after valve ablation to exclude the possibility of remnant valves, reassess Vesicoureteral reflux and postfulguration stricture.[14],[15] Some authors suggest doing routine cystoscopy in follow-up as it may help to diagnose the residual valves as well as serve to be therapeutic in case of residual valves.[7] However, there is a need of repeat anesthesia, it is more invasive and more expensive as compared to MCUG. MCUG is also an invasive procedure, associated with increased exposure to radiation, increased risk of UTI and is often difficult for the patient and the parents to cope up with the stress associated with the procedure. Therefore, we planned to assess the bladder wall thickness before and after fulguration and evaluate its utility to assess the adequacy of fulguration of valves.

In our study, we evaluated a total of 31 patients during the study period. The disease may manifest in a wide spectrum as the age at the presentation varied from 1 day to 10 years with a median of 1 year which is similar to the various literature published previously. The most common group being infants (48%) followed by more than 1 years (39%) and neonates (13%). A study by Bani Hani et al. showed most common presenting age group as neonates (65.7%).[16] However, they had excluded age more than 1 year in their study. A similar study by Gupta et al. had neonates (46.67%) as the most common group.[17] In another study by Menon et al., there were 53 (29.5%) neonates (mean 12 days), 61 (33.5%) patients between 1 month and 1 year (mean 5.5 months), 46 (25.5%) between 1 and 5 years (mean 2 years 7 months), and 21 (11.5%) between 5 and 12 years (mean 8 years–3 months).[18] The most common complaints at the time of presentation in our study were straining (35.48%) followed by antenatally diagnosed patients (25.81%) and recurrent UTI (19.36%). In the study by Bani Hani et al., 45.7% patients were diagnosed antenatally. Gupta et al. reported 30% of patients being diagnosed antenatally in their study. The data suggest the lack of adherence to routine antenatal visits as well as about difficulty to diagnose PUV on antenatal ultrasound in developing country. Presenting complains may vary with the age of presentation. Since, in our study, infants were the most common age group. The presentation was straining during micturition. This is possibly due to parents being able to relate more to straining during micturition in infants than in neonates.

The median urea at the presentation was 28 mg/dL with a range of (6–110) mg/dL and median creatinine at presentation was 0.46 mg/dL with a range of (0.09–5.62) mg/dL suggesting a varied severity at the time of presentation.

Prefulguration median urethral ratio was 2.45, range (0.54–6.97). Postfulguration urethral ratio was available for 27 patients with a median of 1.20, range – (0.46–2.79). Postfulguration urethral ratio was not available for four patients. These consisted of one patient lost to follow-up, one patient did not follow-up for the second visit in the study duration, one patient had earlier undergone fulguration in our institute, and there were no residual fulguration, one patient had persistent urosepsis and underwent vesicostomy before the 3 months' follow-up period. In the study by Bani Hani et al., the postoperative ratio of 3.1 (range 1.9–4) was consistent with adequately fulgurated valves according to their study.[16] Similar study was done by Gupta et al. in 30 patients of PUVs. In prefulguration group, mean urethral ratio was 4.94 (±2.97) and in postfulguration group was 2.134 (±1.19) (P < 0.001).[17] Menon et al. suggested a postoperative urethral ratio >3 SD (1.92) is indicative of incomplete fulguration or stricture.[18] Our review of literature suggests that there is a lot of variation in prefulguration and postfulguration urethral ratio in different studies.[16],[17],[18],[19] The studies by Bani Hani et al. and Gupta et al. had the higher values of urethral ratio prefulguration and postfulguration. However, our values were closer to the values suggested by Menon et al. in their study.

The variation in the values of urethral ratio may be attributed to age at the presentation and method of doing MCUG and ethnicity. However, we could not find any data that have been studied in this context. The urethral ratio can be calculated in PUV patients of different countries to further evaluate this.

The comparison of urethral ratio pre- and postoperatively showed a statistically significant reduction (P = 0.000034). Therefore, we recommend that urethral ratio can be considered objective criteria for assessing the adequacy of fulguration of urethral valves. Area under the curve is 0.87, with a 95% CI − 0.73–1.0 for ROC plotted for urethral ratio. Urethral ratio of 1.20 has got a sensitivity of 87.5% and specificity of 54.5%, whereas urethral ratio of 1.25 has got sensitivity of 68.8% and specificity of 81.8% in predicting the residual valves after fulguration. We further evaluated our data taking urethral ratio of 1.20 and more as suggestive of residual valves and compared it with our cystoscopic findings. It has a sensitivity of 70%, specificity of 54.5%, positive predictive value of 73.60%, negative predictive value of 75%, and likelihood ratio of positive test was 1.54, which is significant. There is no literature available till date as per the best of our knowledge to assess the validity of urethral ratio in predicting the residual valves after fulguration.

Bladder wall hypertrophy is sequelae of bladder outlet obstruction, and hence, it is very logical to consider it as indicator to assess bladder outlet obstruction.[9] Ultrasound has been shown to be sensitive in detecting hydronephrosis and thickened bladder wall.[20] The reference values for healthy children using up-to-date ultrasound equipment are scarce.[21] The greatest detrusor thickness is seen when the bladders were nearly empty. The range of detrusor thickness varies greatly in filling interval. The largest interobserver variability was found when the bladder was nearly empty.[21] Kaefer et al. recorded a bladder thickness index by dividing the average wall thickness (dome, floor, and two lateral wall measurements) by the inner diameter (anteroposterior and transverse measurements).[22] However, such calculations may be tedious.

In another study of 150 healthy infants to teenagers, dorsal DWT ranged from 0.4 to 1.9 mm and ventral DWT from 0.4 to 2.3 mm. DWT increased with age and increasing bladder filling volume. Based on these findings, the authors suggested a DWT reference value of 1.5 mm in asymptomatic children younger than 2 years when measured at the dorsal wall with a greater than 10% volume-filled bladder. In children 2 years old or older, dorsal and ventral DWT for all ages should be 2 mm or less at bladder filling up to 50% or 1.5 mm or less at greater bladder filling.[21] If there is no methodological discrepancy, bladder wall thickness and DWT can be used effectively as a noninvasive test for assessing lower urinary tract conditions.[10]

We evaluated Bland Altman analysis to see for agreement between urethral ratio and bladder wall thickness before fulguration. The SD of the observed parameters is within the limits of agreement of the Bland Altman analysis indicating a good agreement between the observed parameters. This adds to the fact that both bladder wall thickness and urethral ratio increase in the presence of disease.

To the best of our knowledge, there is no literature available currently that has evaluated bladder wall thickness as a diagnostic modality to assess the presence of residual valves. In our study, prefulguration median was 4 mm, range – (1.9–8) mm. Postfulguration bladder wall thickness was available for 27 patients with a median of 2.5 mm, range – (1.2–8) mm. Postfulguration bladder wall thickness was not available for four patients, same as described above. The comparison of bladder wall thickness preoperatively and postoperatively showed a statistically significant reduction (P = 0.000173). Therefore, we recommend that bladder wall thickness can be considered as objective criteria for assessing the adequacy of fulguration of urethral valves. We find it superior to urethral ratio as the procedure is noninvasive, there is no increased risk of UTI, it is less troublesome to the patient and attendants and it is not associated with any exposure to ionizing radiation. Area under the curve was 0.72, with a 95% CI of 0.52–0.92 for ROC plotted for bladder wall thickness. Bladder wall thickness of 1.95 mm has got a sensitivity of 80% and specificity of 45.5%, whereas bladder wall thickness of 3.05 mm has got sensitivity of 46.7% and specificity of 81.8% in predicting the residual valves after fulguration as per the ROC curve.

We further evaluated our data taking bladder wall of 1.95 mm and more as suggestive of residual valves and compared it with our cystoscopic findings. It had a sensitivity of 70%, specificity of 54.5%, positive predictive value of 73.60%, negative predictive value of 75%, and likelihood ratio of positive test was 1.54, which is significant.

We recommend that bladder wall thickness can used as a screening test for assessing the residual valves. MCUG and cystoscopy can be reserved for symptomatic or nonimproving patients who do not have residual valves as per the values of bladder wall thickness on ultrasound. In our study, we did ultrasound immediately after fulguration when the catheter was in situ to ensure full bladder at the time of scan. The prefulguration wall thickness served as a control for the same patient. Since the readings were taken on a distended bladder, the bias of change in the thickness of bladder during the different phases of bladder filling was eliminated. In patients of PUV, bladder wall thickness is uneven so we calculated the values at the dome and left and right trigone. The average of these readings was considered as final bladder wall thickness. We would also like to highlight the importance of adhering to the precautions taken while calculating bladder wall thickness for having results to be reproducible.

We suggest a stepladder approach of using bladder wall thickness on ultrasound, urethral ratio, and check cystoscopy. This minimizes the risk of invasive procedure, increased exposure to ionizing radiation, increased risk of UTI associated with MCUG, psychological trauma associated with MCUG, need for repeat general anesthesia, and cost of hospital stay.

Our study had skewed data because of less number of patients and wide spectrum of the disease. Therefore, we had used median and interquartile range to depict the measure of central tendency and used Wilcoxon signed-rank test to evaluate the change in the bladder wall thickness and urethral ratio after fulguration.


   Conclusion Top


The assessment of residual valves in patients of PUV remains controversial with the availability of different modalities at our disposal. Urethral ratio is a simple and objective method to assess the residual valves. Postfulguration urethral ratio of more than 1.2–1.4 should raise a suspicion of residual valves and warrants a check cystoscopy in these patients. Bladder wall thickness can be used as an objective screening tool to assess the presence of residual valves. It can help to limit the trouble of repeated MCUG and cystoscopy in patients of PUV. Hence, decreasing the pain of invasive procedure, amount of radiation received while repeating MCUG, and also decreasing the need for repeat general anesthesia in repeat cystoscopy. Bladder wall thickness of more than 1.95 mm should raise a suspicion of residual valves. A step ladder approach, including bladder wall thickness, urethral ratio in MCUG, and check cystoscopy, can serve as a new diagnostic algorithm for the assessment of residual valves.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Uthup S, Binitha R, Geetha S, Hema R, Kailas L. A follow-up study of children with posterior urethral valve. Indian J Nephrol 2010;20:72-5.  Back to cited text no. 1
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