|Year : 2023 | Volume
| Issue : 6 | Page : 486-492
Pattern of preoperative uroflowmetry in hypospadias patients and age-matched control patients
Rupesh Sikchi, Arvind Sinha, Manish Pathak, Kirti Kumar J. Rathod, Avinash S Jadhav, Rahul Saxena
Department of Pediatric Surgery, All India Institute of Medical Sciences, Jodhpur, Rajasthan, India
|Date of Submission||13-Dec-2022|
|Date of Decision||08-Jul-2023|
|Date of Acceptance||29-Jul-2023|
|Date of Web Publication||02-Nov-2023|
Department of Pediatric Surgery, All India Institute of Medical Sciences, A 602 AIIMS Residential Complex, Jodhpur - 342 005, Rajasthan
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: Patients with hypospadias often present with voiding difficulties after successful repairs. We sought to analyze the degree of uroflowmetric anomalies that may be present in children with hypospadias before a surgical repair. We, thus, undertook this study to compare the pattern of preoperative uroflowmetry study in hypospadias patients and a comparable age-matched control group.
Materials and Methods: A total of 90 children underwent preoperative uroflowmetry in the Department of Pediatric Surgery at All India Institute of Medical Sciences (AIIMS), Jodhpur, India, between January 2019 and December 2020. Thirty patients with hypospadias and sixty age-matched controls who presented to the outpatient department without any associated urological or neurological anomalies were included in the study. Uroflowmetry parameters such as maximum urine flow rate (Qmax), average urine flow rate (Qavg), voided volume (VV), urination duration, duration of reaching maximum speed, and urine flow curves of the cases and the control group were measured and compared.
Results: The median age of patients at the time of uroflowmetry in the hypospadias group was 7 years, while the same for the control group was 7.5 years. Median maximum urinary flow rates (Qmax) (10.7 vs. 14.45 mL/s, P = 0.01278), average urinary flow rates (Qavg) (6.5 vs. 8.5 mL/s, P = 0.0124), the ratio of maximum urinary flow rates with VV (Qmax/VV) (0.043 vs. 0.053, P = 0.0264) was found to be significant (P < 0.05). These values were significantly lower in the hypospadias group (P < 0.05). The voiding time (43.5 vs. 30 s, P = 0.0285) was significantly higher in the hypospadias group. However, there was no difference in the VV per micturition (219.5 vs. 270.0 mL, P = 0.40) and time to maximum flow rate (10 vs. 10, P = 0.43). Flow curve pattern analysis revealed plateau-shaped curves in 60% of the hypospadias group compared to 27% in the control group, while bell-shaped curve was seen in 37% of the hypospadias group as compared to 65% in the control group which were statistically significant (P = 0.003415). No statistically significant association was found between meatal localization and the uroflowmetry parameters.
Conclusion: Children with hypospadias have abnormal uroflowmetry even before surgical correction and have a significantly low maximum urine flow rate. These uroflow anomalies may be due to meatal stenosis or hypoplastic proximal urethra. We postulate that these preoperative abnormal uroflow patterns in patients with hypospadias may contribute to voiding difficulties in repaired hypospadias cases. A greater understanding of the factors behind these uroflowmetric anomalies may allow surgeons to proactively tackle these intraoperatively, leading to better outcomes for patients with hypospadias.
Keywords: Hypospadias, pediatrics, urodynamics
|How to cite this article:|
Sikchi R, Sinha A, Pathak M, J. Rathod KK, Jadhav AS, Saxena R. Pattern of preoperative uroflowmetry in hypospadias patients and age-matched control patients. J Indian Assoc Pediatr Surg 2023;28:486-92
|How to cite this URL:|
Sikchi R, Sinha A, Pathak M, J. Rathod KK, Jadhav AS, Saxena R. Pattern of preoperative uroflowmetry in hypospadias patients and age-matched control patients. J Indian Assoc Pediatr Surg [serial online] 2023 [cited 2023 Nov 28];28:486-92. Available from: https://www.jiaps.com/text.asp?2023/28/6/486/389323
| Introduction|| |
Hypospadias is a congenital malformation characterized by the presence of the urethral meatus on the ventral surface of the urethra. However, there is a plethora of “field” defects in penile development associated with it, including an abnormally or underdeveloped ventral penile tissue, chordee, and glanular anomalies in children with hypospadias. In these patients, the urethra is less distensible due to a partially absent or structurally abnormal spongiosal body.
Uroflowmetry is a simple and noninvasive investigation used in the evaluation of urinary stream and urethral and bladder function. A normal uroflow curve mostly excludes anatomical urethral obstruction as well as functional voiding disturbances. Considering that most patients with hypospadias have normal bladder contractility, we believe that any abnormalities in urinary flow rates, as well as the shape of the flow curve in these patients, would reflect abnormal urethral function.
Numerous previous studies have proposed uroflowmetry as a tool for the evaluation of postoperative results for hypospadias repair. Studies have established that patients with repaired hypospadias demonstrate an obstructive flow pattern in varying numbers of cases (7% to 67%). Possible explanations for this postoperative flow pattern abnormalities could be a lack of muscle covering in neourethra, the presence of surrounding scar tissue, reduced distensibility of the neourethra with consequent possible turbulent flow and eddy currents, meatal stenosis, or a narrowing of the urethral lumen or urethral stricture as a complication of hypospadias surgery.,,, However, the question of whether the postoperative abnormal uroflow in hypospadias patients may be contributed by a preexisting generalized “field” defect as part of urethral malformation or is a result of the operative intervention remains unanswered.
This study aims to establish a baseline uroflow pattern achieved by a child with hypospadias before any operative procedure has been performed. We also wished to compare it with an age-matched control group.
| Materials and Methods|| |
Thirty preoperative pediatric patients with hypospadias constituted the study population and 60 age-matched healthy boys with no neurological or urological anomalies constituted the control group. Considering the Mean Qmax/voided volume (VV) as 0.215 (standard deviation [SD] 0.13) in hypospadias and 0.7675 (SD 0.6175) in controls in the study conducted by Olsen et al., the estimated sample size calculated was 30 hypospadias group and 60 in control groups (1:2 ratio of cases to control group) at 95% confidence interval, 80% power and 10% contingency. The study was done in Pediatric Surgery Outpatient Department between January 2019 and December 2020. Institutional ethical clearance was granted for conducting the study (vide reference number– AIIMS/IEC/2018/806). All children included in the study were boys older than 3 years of age and were toilet trained. Previously operated cases of hypospadias, patients suffering from urinary tract infection, patients with neurogenic bladder, or any patients with any associated neurological or urological abnormality related to the bladder, which could potentially affect flow pattern, were excluded from the study.
Clinical details of all the patients were recorded as per predetermined proforma. Informed consent was taken from all the parents or guardians. Uroflowmetry was performed on a uroflowmetry system (Netherland, Laborie medical technology, Nexam Pro UDS-01710259) in combination with a computer and Medical Measurement System software program. The Uroflow meter was placed in a private and quiet place. The children were kept well hydrated and a commode chair and uroflow stand with a funnel were placed on the flow sensor. Participants were asked to present with a full bladder (holding urine), and the test was performed when the child had a normal sensation of urinating. Participants were advised to void in the natural standing position into the funnel when they felt a natural desire and when the operator told them to start voiding.
Patients with insufficient voids (<50 mL), grossly abnormal flow shapes, or abnormal maximum urinary flow rates (Qmax) were asked to repeat the uroflow study. Each participant was asked to void another time after an adequate gap and the higher values of the two consecutive Qmax values of the same child with a VV of ≥50 mL were included in the study. Expected bladder capacity was calculated using the formula (age [year] +1) × 30 as recommended by the International Children's Continence Society (ICCS).
The uroflowmetric parameters studied during the test were the maximum urinary flow rates (Qmax), average urinary flow rates (Qavg), total VV, voiding time, time to maximum flow rate, and flow curve pattern. The flow curve classification accepted by the ICCS was used for the evaluation of uroflowmetry results. A representative uroflowmetry curve was usually selected for each patient from the one with the larger VV. The various uroflow parameters and flow patterns were studied based on the uroflowmetry study. A normal flow curve was defined as a flow rate with a Qmax >25th percentile for age with a normal bell-shaped curve. An equivocally obstructed flow rate was considered if the Qmax was between the 5th and 25th percentile for age. An obstructed flow study had a Qmax lower than the 5th percentile for age with an obstructed flow curve. Statistical analysis of the data was performed between hypospadias patients with age-matched control patients using Statistical Package for the Social Sciences version 23 software program (SPSS 23-IBM Corp. Released 2015. Statistics for Windows, Version 23.0. Armonk, NY, USA. IBM Corp.)
Results were presented as medians (range). Uroflow parameters and urine flow patterns between both groups were compared using the Mann–Whitney U-test and Chi-square test. A P < 0.05 was considered statistically significant.
| Results|| |
The median age of patients at the time of uroflowmetry in the hypospadias group was 7 years (Interquartile Range [IQR] =5.5), while the same for the control group was 7.5 years (IQR = 4).
The location of the meatus was also evaluated in the patients with hypospadias and the figure presents the distribution of the hypospadias patient of our cases according to the location of meatus [Figure 1].
|Figure 1: Distribution of the location of meatus among patients with hypospadias and their numbers|
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Hypospadias patients were further classified according to the classification into anterior, middle, and posterior [Figure 2]. Thirty three percent of the patients (n = 10) had an anterior meatal location, 63% (n = 19) had a mid-penile meatus and one patient had a posterior penile location
|Figure 2: Distribution of cases according to the location of meatus on the penis|
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The 30 cases diagnosed with hypospadias were investigated in terms of preoperative uroflowmetry results. These results were compared with the uroflowmetry results of the control group, which included 60 age-matched control children. Uroflowmetry findings of these cases are shown in [Table 1]. Mann–Whitney test was used to look for statistically significant differences between the hypospadias group and the control group. Qmax, Qavg, Qmax/VV, and voiding time were found to be statistically significant (P < 0.05).
|Table 1: Cardinal uroflowmetry parameters in the hypospadias and control groups|
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The urine flow rates in the hypospadias and the control groups were evaluated according to Toguri Normograms, with a normal flow rate being considered as a Qmax >25th percentile for age. Obstructed flow rates were a Qmax level <5th percentile for age and the patients with flow rates (maximum) between 5th and 25th percentile were classified as an equivocal obstructed flow rate.
Urine flow rates according to the Toguri nomogram are presented in [Table 2].
The urine flow curves of the patients were also evaluated and the curves were classified as bell-shaped, plateau shaped, or intermittent [Figure 3], and the results are presented in [Table 3]. The comparison was made between bell shape and plateau shape curve patterns. One child with an intermittent flow curve pattern was excluded from the comparison (n = 1).
The measured flow curves were compared to the absolute uroflowmetry values (Qmax, Qavg, Qmax/VV, and voiding volume). The Qmax, Qavg, and voiding time were significantly different (P < 0.01) in the bell curve group as compared to the plateau group with a higher maximum and average urine flow rate (Qavg and Qmax) and a lower voiding time in the bell curve group. The time to Qmax was significantly higher in the plateau group (P < 0.05) Thus, the flow curve patterns correlated well with the measured uroflowmetry values.
On comparing the uroflowmetry parameters with the location of the meatus no statistically significant difference was found in the parameters according to the location.
| Discussion|| |
The Standardization Committee of the ICCS has defined five types of flow patterns in uroflowmetry. Each pattern is not specific to an underlying diagnostic abnormality but rather serves as a guide to the existence of a specific condition. In normal voiding, the curve is smooth and bell-shaped. A child with an organic outlet tract obstruction often has a low amplitude, even flow curve, which is a plateau-shaped curve.
Toguri et al. in 1982 determined percentile nomograms for Qmax, Qavg based on body surface area (BSA), VV, and sex by studying uroflow parameters in more than 1000 children. The nomograms of Toguri, which were developed by comparison of the urinary flow rate to BSA and age, have been accepted as a reliable tool for diagnosing voiding abnormalities through uroflowmetry. In Toguri nomograms, a uroflow pattern is considered obstructed if the flow rates are lower than the 5th percentile for age and considered equivocal if it lies between the 5th and 25th percentile. Any value above the 25th percentile for age is considered normal.
Various previous studies have reported on to results of preoperative uroflow studies in patients with hypospadias.,,,,,,, In the present study, we compared the 30 preoperative uroflowmetry patterns and parameters of hypospadias patients with 60 age-matched control patients. Three previous studies have similarly compared preoperative uroflowmetry of hypospadias patients with age-matched control.,,
The localization of the Hypospadiac urethral meatus in the present study was almost similar to the distribution given in the study by Piplani et al. However, it differed from other studies conducted by Oztorun and Tiryaki and Perera et al. This may reflect the differing case selection criteria or a distinct and unique disease profile across geographies.
ICCS has regarded maximum urinary flow rate (Qmax) as one of the most relevant parameters of uroflowmetry while assessing bladder outflow obstruction. Qmax serves as an important parameter in monitoring the effectiveness of medical and surgical treatment for voiding dysfunction. Qmax is the most relevant quantitative variable and is considered significant only when a peak flow has been sustained for more than 2 s.
Piplani et al., in their study on patients with hypospadias, found that more than 50% (14/26) patients had preoperative Qmax <5th percentile with a mean Qmax of 10.3 mL/s, and 65% (17/26) of patients had plateau curve pattern.
Similarly, Oztorun and Tiryaki in another study on patients with hypospadias, found that the preoperative Qmax in patients with hypospadias was 11.5 mL/s. Their results indicated that the abnormal urodynamics and partial obstruction in the urethra are preexisting in patients with hypospadias.
A similar study in infants also concluded that 38% (8/21) of infants with hypospadias void with low median Qmax of 2.4 mL/s with plateau-shaped curves, as against none in the control group who had a median Q max of 4.4 mL/s.
Malyon et al. also evaluated 90 patients with hypospadias on 140 occasions and similarly observed low flow rates and flattened uroflowmetry curves in the population with hypospadias compared to the controls.
We also found that the median maximum urine flow rate (Qmax) in the group with hypospadias was 10.7 mL/s, which was significantly lower than the age-matched controls who had a median maximum urine flow rate of 14.45 mL/s.
The average flow rates (Qavg) in the hypospadias group were 6.5 mL/s and were lower than that in the control group and were statistically significant (P = 0.0124). This finding was also consistent with other similar studies in the literature.,,
Adequate VV is an important clinical parameter and is affected by the estimated bladder volume and the residual urine and an adequate VV is correlated positively with an adequate uroflowmetric evaluation. In the present study, the VV in the hypospadias group and controls were compared. It was 219 mL in the hypospadias group and 270 mL in the control group. Similarly, Oztorun and Tiryaki had a VV of 186 mL in hypospadias patients. In another study by Olsen et al., the largest VV for hypospadias infants was found to be lower than normal infants.
Qmax and Qavg are inherently related to VV. The flow rate increases with an increase in VV. Similarly, the variation around the mean flow rate increases with VV. VV changes significantly with age, especially in the 5 to 15-year age group. The Qmax/VV ratio was specifically used to eliminate the factor of rising VV on rising flow rate with age. In the present study, preoperative Qmax/VV of hypospadias patients was significantly lower compared to the control group. This finding was in concordance with other similar studies in the literature.,
If there is an obstruction to the outflow of urine either at the level of the bladder or urethra, it might present with an increase in the voiding time. Similarly, voiding time increases in operated cases of hypospadias presenting with urethral stricture and meatal stenosis. In the cohort group, about 6 (20%) hypospadias patients had visibly narrow meatus. However, on history, there was no straining or difficulty in passing urine. Our cohort demonstrates a significantly higher voiding time in the hypospadias group even before the surgical repair as compared to the control group. The median voiding time was also found to be higher in comparison to controls and is borne out by similar studies in the literature., The lower levels of maximum and average flow rates, along with a prolonged voiding time in our cohort with hypospadias, suggest that these patients of hypospadias may have a preexisting fixed outflow obstruction.
The flow curve patterns may be affected by the inherent detrusor contraction strength, any abdominal straining, and bladder outlet resistance. However, there can be large inter-and intra-observer variability in the interpretation of uroflowmetry curves. In the present study, 60% (18/30) of hypospadias patients showed plateau-shaped curves, 37% (11/30) hypospadias patients showed bell-shaped, and 3% (1/30) patients showed intermittent patterns preoperatively. The urine flow curve pattern findings in our study were like the study by Piplani et al. However, Wolffenbuttel et al., Olsen et al., and Oztorun and Tiryaki had a different composition of types of urine flow curve patterns in their population.,, Oztorun and Tiryaki had a predominant bell shape curve pattern in hypospadias patients, while Olsen et al. and Wolffenbuttel et al. predominantly had intermittent-shaped flow curve patterns in their study.,,
To ensure that the subjective uroflow curve patterns correlated with the observed uroflowmetry values, we used the observed uroflowmetry values and compared it with the observed flow patterns. On comparison of the flow pattern (Bell shape and plateau shape) with the uroflowmetry parameters such as Qmax, Qavg, Qmax/VV, voiding time, and time to Qmax, there was a good positive correlation between flow curve patterns and uroflowmetry parameters. These findings were similar to studies conducted by Marte et al. and Kaya et al.,
In the present study, 65% (39/60) of patients from the control showed a bell-shaped flow curve pattern, 27% (16/60) showed a plateau shaped, and 8% (5/60) showed an intermittent pattern preoperatively. The urine flow curve pattern findings in controls were consistent with the study conducted by Piplani et al. but inconsistent with other studies conducted by Olsen et al.
According to Toguri nomograms, in the present study, the hypospadias patient showed preoperative obstructive pattern in 50% (15/30) patients and had a plateau/flat curve pattern in 60% (18/30) patients. This was like the findings of the study by Piplani et al. They had more than 50% (14/26) patients had preoperative Qmax <5th percentile and 65% (17/26) patients had a plateau curve pattern.
The meatal location did not affect the pattern of the urine flow curves.
Limitation of the study
The number of cases was limited in the present study. This is a nonrandomized observational study that included cases and age-matched controls and they were analyzed prospectively. The residual urine amount in the bladder after urination was also not measured. Although meatal stenosis was evaluated clinically based on appearance and symptoms, the exact size of the meatus was not calculated or calibrated in the study. Both the meatal size, including stenosis, and the amount of residual urine, may affect the uroflow patterns.
| Conclusion|| |
Uroflowmetry remains a useful tool in screening for abnormal urethral function in hypospadias preoperatively. Hypospadias patients can and do demonstrate an obstructive urine flow curve pattern uroflowmetry even before a surgical correction. Hypospadias patients have significantly low maximum urine flow rate, average flow rate, Qmax/VV, and a higher voiding time than their control group. Hypospadias patients have approximately 25% lower maximum urine flow rates than their age-matched controls. Various positions of meatus did not appear to alter the uroflowmetry parameters in the present study. These uroflow anomalies may be due to an underlying outflow tract obstruction and may be due to a variety of factors such as meatal stenosis, hypoplastic proximal urethra, or other hitherto unnoticed associated factors. These factors may go on to further contribute to voiding difficulties in repaired hypospadias cases. A better understanding of these factors may allow surgeons to better tackle the causative factors intraoperatively, leading to potentially better surgical outcomes in patients with hypospadias.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]