Focused non-invasive assessment of lower urinary tract dysfunction among children with cerebral palsy

INTRODUCTION

Cerebral palsy (CP) refers to a group of disorders caused by permanent but non-progressive injury to the developing fetal or infant brain, resulting in disturbances of movement and posture. While the primary brain insult remains static, the clinical manifestations may evolve due to musculoskeletal changes, growth, and secondary complications.^[1] CP is a leading cause of childhood disability worldwide, with a significant burden in low- and middle-income countries. A recent systematic review and meta-analysis estimated the prevalence of CP in Indian children to be 3.1/1000 live births,^[2] highlighting the need for context-specific data to inform care strategies.

Urinary continence in children is regulated by complex coordination between the autonomic and somatic nervous systems and cortical control over the brainstem micturition center. It is achieved as the brain–bladder axis matures, enabling voluntary control over voiding.^[3] Children with CP frequently face neurological impairments that disrupt this pathway, increasing the risk for lower urinary tract dysfunction (LUTD), including urinary frequency, urgency, incontinence, and recurrent urinary tract infections.^[4] Standardized terminology for pediatric lower urinary tract function has been established by the International Children’s Continence Society, which facilitates uniformity in assessment and diagnosis.^[5]

Despite the high frequency of urinary symptoms in CP, invasive urodynamic evaluations are often avoided due to poor cooperation, cognitive limitations, and discomfort.^[6] Noninvasive alternatives, such as ultrasonographic assessment of post-void residual urine (PVR) and bladder wall thickness (BWT), are gaining attention. Elevated PVR and increased BWT have been associated with detrusor overactivity, poor bladder compliance, and increased risk for upper urinary tract deterioration in both pediatric and adult female populations.^[7-9]

Previous studies have shown variability in the reported prevalence of LUTD among children with CP, ranging from 30% to over 60%.^[4,9] These differences reflect varying diagnostic criteria, study designs, and populations. Few studies have used non-invasive ultrasound-based parameters such as aBWT and PVR to objectively quantify LUTD specifically in Indian children with CP, despite the potential of these tools to provide reliable data without causing distress to patients or caregivers.

MATERIALS AND METHODS

This prospective cross-sectional observational study was conducted from June 2023 to May 2024 in the departments of pediatrics and urology at a tertiary care teaching hospital in Northeast India. The study received prior approval from the Institutional Ethics Committee (IEC-M3/F46/2023), and the study protocol was not registered in a public observational study registry. Written informed consent was obtained from the parents or legal guardians of all participants. Assent was sought and documented from children above 7 years of age who were developmentally capable of providing it.

Children diagnosed with CP were recruited consecutively from the pediatric outpatient department, and age- and sex-matched neurologically healthy controls were enrolled from among patients attending the general pediatrics clinic for non-neurological concerns such as nutritional or minor respiratory issues. The inclusion criteria for the CP group were children aged 4–12 years with a confirmed diagnosis of CP, based on clinical history and examination in accordance with the surveillance of CP in Europe criteria, and confirmed by a pediatric neurologist. Controls were frequency-matched for age and sex and had no known neurological, urological, or developmental disorders. Exclusion criteria for both groups included any history of prior urological surgery, current or recent urinary tract infection (confirmed by urinalysis and clinical symptoms), severe intellectual disability preventing questionnaire participation, drug-resistant epilepsy, and those requiring intensive care. Children with spinal dysraphism or structural urinary tract anomalies on ultrasound were also excluded from the study.

All children underwent detailed clinical evaluation by a pediatrician trained in neurodevelopmental assessment. The examiner was blinded to the group allocation during examination. The GMFCS level was assigned based on observation and caregiver report, using the standardized GMFCS-E and R scale. Developmental quotient (DQ) was assessed using the Vineland Social Maturity Scale, administered by a clinical psychologist. Demographic data, clinical subtype of CP, history of bladder and bowel symptoms, and prior treatments were documented.

BBD symptoms were assessed using the DVSS, a validated tool consisting of 10 symptom items plus a stress and self-esteem question. The Indian validated Hindi translation of the DVSS was used where applicable. Cutoff scores of >6 for females and >9 for males were used to define abnormal results, as per original validation standards. The DVSS was administered as an interview-based tool by the investigator, with help from caregivers and a pediatric nurse when needed. The DVSS was analyzed both as a continuous variable and dichotomized for the presence/absence of BBD in secondary analyses. Reproducibility and limitations of DVSS in neurologically impaired populations were acknowledged and accounted for in the interpretation of findings.

Ultrasound measurements were performed using a Samsung HS30 ultrasound system equipped with a 3–5 MHz curvilinear transducer. The assessments were performed in the supine position under standardized conditions by a single experienced radiologist blinded to both DVSS scores and participant group (case/control). Expected bladder capacity (EBC) was estimated using the formula: (Age in years + 2) × 30 mL. BWT was measured when bladder filling was between 50% and 115% of EBC to avoid under- or over-distension. The percentage bladder filling was calculated using actual pre-void bladder volume (length × width × height × 0.5236) as a proportion of EBC. The thresholds for under-distension (<50%) and over-distension (>115%) were based on published pediatric urological imaging standards.

BWT was measured in millimeters (mm) using the inner-to-inner method of the hypoechoic detrusor muscle layer, excluding serosa and mucosa. Three separate measurements were taken from the anterior, posterior, and lateral bladder walls, and the average value was recorded as aBWT. PVR was measured within 5 min after voiding using the same volume calculation formula. PVR was considered significant if it exceeded 30 mL or 21% of EBC for children aged 4–6 years, or more than 20 mL or 15% of EBC for children aged 7–12 years, as per standard pediatric thresholds.^[10,11]

If the initial PVR was elevated, a second measurement was performed to confirm. A random subset of 10% of ultrasound studies was re-measured for intra-observer reliability; the intraclass correlation coefficient for aBWT measurements was found to be 0.91, indicating excellent reliability [Figure 1].

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Figure 1:

Ultrasound assessment of the urinary bladder in a child with cerebral palsy. Representative B-mode ultrasonographic images of the urinary bladder obtained using a Samsung HS30 machine with a 3–5 MHz curvilinear transducer, in supine position under standardized bladder filling conditions. (a) Transverse view of the urinary bladder showing length and width measurements used to estimate bladder volume using the ellipsoid formula (length × width × height × 0.5236). (b) Midline longitudinal view showing measurement of the bladder height. (c) Transverse image showing wall thickness measurements of the right and left lateral bladder walls. (d) Longitudinal image showing wall thickness measurements of the anterior bladder wall (indicated by arrow) and posterior wall (indicated by arrowhead). The average bladder wall thickness was calculated as the mean of four measurements: anterior, posterior, right lateral, and left lateral wall thicknesses. Measurements were taken when the bladder was filled between 50% and 115% of expected bladder capacity to avoid under- or over-distension.

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The sample size was calculated using a standard formula for comparing two proportions. Based on a prior study indicating a 60.8% prevalence of LUTD among children with CP,^[12] assuming a 95% confidence interval (CI), power of 80%, and a minimum detectable difference of 30% between groups, the required sample size was 41 subjects per group. The formula used was:

n = [(Zα/2 + Zβ)² × (p1(1−p1) + p2(1−p2))]/(p1−p2)²,

Where P1 = 0.608 (CP group), P2 = 0.30 (control group), Zα/2 = 1.96, Zβ = 0.84. A total of 82 children (41 in each group) were thus included.

Statistical analysis was performed using IBM Statistical Package for the Social Sciences version 25.0. Normality of continuous variables was assessed using the Shapiro-Wilk test. Variables following normal distribution were compared using Student’s t-test, while non-parametric variables were compared using Mann–Whitney U test. Categorical data were compared using the Chi-square test or Fisher’s exact test where appropriate. Pearson’s correlation coefficient was used to assess the relationship between DVSS scores, aBWT, and PVR. Equality of variances was tested using Levene’s test. No multivariable regression modeling was conducted due to the limited sample size and non-longitudinal nature of the study; instead, stratified subgroup analyses were performed. A two-tailed P < 0.05 was considered statistically significant. No adjustments were made for multiple comparisons due to the exploratory nature of the study.

RESULTS

A total of 82 children were enrolled in the study – 41 with CP and 41 age- and sex-matched neurologically healthy controls. The median age in both groups was 8 years (interquartile range [IQR]: 6–10 years), and the distribution of males and females was identical (68% males, 32% females). The groups were comparable in terms of age (P = 0.91), sex (P = 1.00), and body weight (mean 18.2 ± 3.5 kg in CP vs. 18.9 ± 3.3 kg in controls; P = 0.42), indicating successful matching [Table 1].

Among the CP group, spastic CP was the predominant subtype (51%), followed by mixed (39%), dystonic (7.3%), and dyskinetic without dystonia (2.4%). The majority of children had severe motor disability, with 78% classified as GMFCS level IV or V. DQs were <70 in 75.6% of the CP group. Microcephaly and seizure history were also common, present in 51% and 83% of CP participants, respectively. No such features were observed in controls. All CP diagnoses were confirmed by a pediatric neurologist, and none of the participants had active urinary tract infections at the time of assessment.

DVSS correlation with aBWT and PVR

Correlation analysis showed a moderate positive association between DVSS scores and aBWT in the CP group (r = 0.617, P < 0.001; 95% CI: 0.38–0.78). A scatterplot with a regression line and 95% CI shading is shown in Figure 2. In contrast, the correlation between DVSS and PVR was weak and not statistically significant (r = 0.184, P = 0.25), supporting the notion that PVR alone may be an insensitive marker of symptomatic LUTD in this population.

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Figure 2:

Correlation between average bladder wall thickness and dysfunctional voiding symptom score (DVSS) in children with cerebral palsy. Scatterplot depicting the correlation between DVSS and average bladder wall thickness (aBWT, mm) in children with cerebral palsy (n = 41). Each dot represents one participant. The red line shows the linear regression line, and the shaded area represents the 95% confidence interval. Pearson’s correlation coefficient: r = 0.617, P < 0.001, indicating a moderate positive correlation between aBWT and symptom severity. X-axis: Average bladder wall thickness (mm). Y-axis: DVSS score (unitless).

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DISCUSSION

The management of children with CP remains complex, requiring lifelong multidisciplinary care involving neurologists, pediatricians, urologists, physiotherapists, and rehabilitation specialists. The presence of cognitive impairments, mobility restrictions, and communication barriers in many children with CP makes invasive diagnostic procedures such as urodynamics particularly challenging. This often results in delayed identification of LUTD, which can have serious consequences, including renal deterioration if unrecognized. In this context, our study provides a feasible and patient-friendly approach to evaluating LUTD using a combination of symptom scoring (DVSS) and focused non-invasive ultrasound assessment, all conducted during a single outpatient visit.

Our findings are consistent with prior research demonstrating a high prevalence of LUTD among children with CP.^[2] In particular, we observed significantly higher DVSS scores, aBWT, and PVR volumes in the CP group compared to controls. These results are in line with the observations by McNeal et al.,^[4] who also used non-invasive methods and reported increased BWT in children with CP. Quantitatively, our mean aBWT values were higher than those reported in some previous pediatric studies,^[7-9] likely reflecting differences in participant characteristics, including a greater proportion of children with severe motor disability (GMFCS IV-V), slightly older mean age, and differences in bladder filling thresholds and measurement protocols.

The relationship between neurological impairment and bladder dysfunction is multifactorial. Spasticity and dystonia may disrupt voluntary sphincter control and coordination between bladder contraction and urethral relaxation, leading to detrusor overactivity and incomplete emptying. Over time, these abnormal voiding patterns may contribute to bladder wall remodeling and thickening, consistent with the elevated aBWT observed in our study.^[7-9] While our study did not directly assess detrusor pressures, the aBWT measurements serve as a surrogate marker in this context. We also observed a moderate positive correlation between aBWT and DVSS scores, supporting the idea that structural bladder changes correspond with symptomatic severity. Conversely, PVR showed a weak and non-significant correlation with DVSS, suggesting that while it may indicate incomplete emptying, it is less sensitive in detecting overall symptom burden.

Constipation was reported in nearly all CP participants in our cohort. Although this prevalence appears high, it reflects a pattern reported in other studies involving children with CP, though with considerable variability.^[13] The bidirectional interaction between constipation and bladder dysfunction is well documented: rectal distension can mechanically compress the bladder or exacerbate detrusor overactivity, while bladder dysfunction can impair bowel habits due to shared neural control. In our study, constipation was assessed using standard criteria, but we acknowledge that caregiver-reported symptoms may be prone to misclassification. Nonetheless, the near-universal presence of bowel dysfunction further supports the need for holistic evaluation of bladder and bowel habits in children with CP.

Our results have important clinical implications. The high burden of LUTD in this population supports the need for routine screening, particularly in children with higher GMFCS levels. Based on our findings and previously reported thresholds,^[7-9] a provisional screening algorithm may involve administering the DVSS during routine visits. If scores exceed age- and sex-specific thresholds, non-invasive ultrasonography for aBWT and PVR could be considered. If aBWT exceeds a defined clinical cutoff or PVR is persistently elevated, referral for formal urodynamic testing and specialist intervention may be warranted. These thresholds should be interpreted cautiously and validated in larger studies before being adopted in clinical protocols.

Our study also highlights several limitations. First, it was conducted at a single tertiary care center, which may limit generalizability. Second, its cross-sectional design prevents any causal inferences regarding the relationship between neurological severity and LUTD. Third, the relatively small sample size limited subgroup analyses and may have reduced statistical power in specific comparisons. Fourth, DVSS relies on caregiver-reported symptoms, introducing the possibility of recall or reporting bias. Fifth, although we ensured radiological blinding, we did not assess inter-observer reliability, as all ultrasounds were conducted by a single radiologist. Finally, the absence of confirmatory urodynamic studies may be considered a limitation; however, our study purposefully adopted a non-invasive approach to reflect real-world clinical constraints in this vulnerable population, consistent with recommendations by pediatric urology societies.^[14]

Future research should focus on longitudinal assessments to determine whether BWT and symptoms improve or progress over time, and whether interventions such as bladder training or bowel management can alter the aBWT or LUTD trajectory. Interventional trials targeting constipation, pelvic floor therapy, or neuromodulation in children with CP and LUTD would be particularly valuable. In addition, further studies are needed to refine and validate ultrasound-based thresholds for screening and monitoring purposes in larger, multicenter cohorts.

In this tertiary care sample from Northeast India, children with CP had significantly higher DVSS scores and aBWT compared to age- and sex-matched controls. Focused non-invasive ultrasound measures, such as aBWT and PVR, may serve as useful initial screening tools for LUTD in this population. However, larger prospective studies incorporating urodynamic evaluation are needed to confirm their predictive value and to establish clinically meaningful thresholds for routine practice.

CONCLUSION

This study elucidates the high prevalence and severity of lower urinary tract dysfunction in children with cerebral palsy (CP). A combined approach incorporating DVSS and focused ultrasound assessment of average bladder wall thickness and post-void residual urine in all children with CP may serve as an effective non-invasive screening tool to identify LUTD early and effectively, thereby facilitating timely treatment and improving their quality of life.