A 15-year retrospective review of urodynamic studies in children at Red Cross War Memorial Children’s Hospital, Cape town, South Africa

Lower urinary tract dysfunction (LUTD) is a common problem causing a major social and psychological burden to both children and their families. If left untreated, some cases of LUTD such as anatomic, neurogenic or severe dysfunctional voiding, may cause irreversible kidney damage. The goal of treatment is therefore aimed at protecting the kidneys and ensuring urinary continence, with direct positive effects for the child’s quality of life [1]. The treatment of LUTD greatly depends upon establishing the correct diagnosis. Traditionally, the evaluation of a child with LUTD includes a history, physical examination, bladder and stool diaries, kidney-ureter-bladder (KUB) ultrasonography and voiding cystourethrogram (VCUG). Unfortunately, there is a sizable proportion of patients in whom conventional approaches fail to provide an explanation of their symptoms.

Urodynamic study (UDS) is used to identify other lower urinary tract (LUT) pathologies where conventional modalities have failed to establish a diagnosis. The major benefit of UDS is its ability to assess the mechanical function of the bladder, sphincter and urethra [2]. Invasive UDS has an advantage over other modalities as the only investigation that is able to assess detrusor pressures during bladder filling and voiding phases. When VUDS is performed, information on both mechanical function and anatomy of the LUT can be obtained [2, 3]. There is compelling data that support its use in patients with neurogenic lower urinary tract dysfunction (NLUTD) [4, 5]. The International Children’s Continence Society (ICCS) now recommends UDS (preferentially VUDS) for all children with spinal dysraphism and those with suspected neurogenic bladder from other causes [4]. Several institutions have now begun to adopt universal rather than risk stratified UDS protocols for children with spinal dysraphism [6].

Invasive UDS is not without its own inherent problems. It involves bladder catheterization, which may cause discomfort and anxiety in a child. Many authors do not recommend its routine use in assessing children with non-neurogenic lower urinary tract dysfunction (NNLUTD) [7, 8]. They argue that UDS does not generally change the management and treatment in these patients, as in most cases a detailed voiding history and physical examination is usually sufficient for a correct diagnosis [7, 8]. It is therefore, suggested that, in these types of patients, UDS be reserved for children who are failing standard therapy or where conventional investigations have failed to provide answers for their symptoms [9]. Some authors support its use in the evaluation of children with recurrent urinary tract infections (UTI) associated with history of voiding dysfunction (frequency, urgency and incontinence) [10, 11].

As the role and demand of UDS in both paediatric urology and nephrology increases, several studies have exposed gaps in the literature [2, 12‐14]. There is also lack of data in the use of UDS in the African context, and current knowledge on urodynamic investigations in the African paediatric population is mainly based on studies done in Europe, North America and Asia. This study was undertaken to describe the 15-year experience with the use of invasive urodynamic studies conducted at Red Cross War Memorial Children’s Hospital (RCWMCH), Cape Town, South Africa during the period September 2005 to September 2020.

The specific objectives for this study are:

This study is a description of a 15-year experience with 1108 invasive urodynamic studies performed at Red Cross War Memorial Children’s Hospital between September 2005 and September 2020. The most important findings of this study are the following: (1) the increasing trends in the use of UDS from 2015; (2) the wide range of indications for urodynamic testing; (3) presence of high risk urodynamic features at first study despite having previously been evaluated using the conventional modalities and receiving multiple bladder treatments; (4) a statistically significant improvement between first time study and follow-up study (post interventional) using low bladder compliance, detrusor sphincter dyssynergia (DSD) and detrusor leak point pressure (DLLP) > 30 cm H₂O.

In the present study, the majority (58.3%) of UDS were performed on male patients with a median age at first study of 7.0 years (range 4.0–11.0 years). A similar sex difference was also reported by Hoebeke et al. and Swithinbank et al. [11, 14]. The observed male predominance can be explained by the fact that LUTDs such as PUV, which accounted for 13.8% of all studies, only occur in male patients. Studies with a female predominance were mainly focusing on the use of UDS in children with NNLUTD such has urge syndrome, dysfunctional voiding etc. [8, 9, 16].

The 15-year results showed increasing trends in the use of UDS. The observed upward trend from 2015 can be explained by the increase of knowledge surrounding the advantages of using the urodynamic studies when evaluating children with LUTD. Previous research corroborates the benefits of utilizing UDS for the diagnosis and management of children with neurogenic lower urinary tract dysfunction [5, 17‐20]. When evaluating 51 patients with closed spina bifida, Johnston et al. demonstrated that clinical neurological assessment, history of voiding habit and renal tract ultrasonography were not reliable indicators of bladder dysfunction compared to VUDS [5]. Tarcan et al. reported that newborns with myelodysplasia and normal bladder function on urodynamics still require follow-up urodynamic testing [17]. Several guidelines including the ICCS, European Association of Urology and the European Society for Paediatric Urology (EAU/ESPU) recommend urodynamic testing for all children with suspected neurogenic lower urinary tract dysfunction [4, 6].

Because of this compelling data on UDS in children with NLUTD, it is not surprising that the majority (62.1%) of urodynamic testing in this study were of children with spinal abnormalities. There may be a preferential referral from the multidisciplinary Spinal Defect Clinic at RCWMCH as the Urologists are the primary discipline at these clinics. A total of 37.7% studies performed were requested by the Urology department. There also seem to be a fair number of referrals coming from other departments, Spinal defect clinic 34.4%, Nephrology 20.8% and other (Oncology, Neurology, Neurosurgery, other hospitals) 7.0%. This finding suggests that the value of UDS has received heightened awareness even in specialties that have historically not involved it. Another notable finding is the small number 49 (4.4%) of patients referred with enuresis as an indication. This might be due to the fact that the centre currently has a tendency of undertaking uroflowmetry first for all functional LUTD and reserving invasive studies for patients not responding to treatment.

The justification for an invasive urodynamic study request is normally based on the assumption that the outcome is likely to affect treatment, when treatment does not lead to its intended outcome or when surgical interventions are planned [7, 10, 12, 21]. The benefits of performing a UDS should also outweigh the risks. The indications for the UDS studies performed are listed in Table 1. The most common reason for UDS were to discern treatment effects (medical 36.5% and surgical 8.5%). The study revealed that at first urodynamic study, 59.1% of children were already receiving more than one type of bladder management. It is evident from this finding that LUTD can be difficult to treat and often requires more than one type of bladder treatment. This observation also raises a concern of delayed referral for some patients. The ICCS advocates a baseline UDS before the age of one year for all patients with spinal dysraphism, even before symptoms start [4]. Early intervention is necessary to decrease significant complications such as end stage kidney disease in these cases. To improve early referral, there should be continued medical education on UDS and quality improvement projects. CIC appears to be the most commonly used method of treatment. This reflects the hospital’s institutional practice of CIC initiation in spinal dysraphism patients at an early age. The most frequently prescribed drug for bladder management was Oxybutynin (305 of 727), compared to Solifenacin succinate (9 of 727) and Mirabegron not being used in any patients in our study. Drug availability and cost might have influenced the choice of medication prescribed. Both Mirabegron and Solifenacin succinate were not available for use in our hospital during the study period as they are not on the drug formulary mainly due to their high cost. However, patients under medical aid cover were able to purchase the medications from private pharmacies.

The remaining UDS were ordered for recurrent UTI (18.6%), VUR (11.2%), baseline study (10.5%), recurrent UTIs associated with VUR (9.9%), pre- and post-transplant (7.0%), pre- surgical intervention (5.7%) and anorectal malformation (4.9%). The clinical significance of invasive UDS in children with NNLUTD still remain the source of controversy in literature [7, 9, 10]. Soygür et al. retrospectively evaluated the role of VUD in the diagnosis and management of voiding dysfunction and found that VUDS did not generally change approach to the patient [7]. In a multicentre controlled trial in children with urge syndrome and dysfunctional, Bael et al. recommends reserving VUD for those who have failed initial treatment [9]. Glazier et al. demonstrated abnormal VUDS in 28 out of 38 children with recurrent UTIs associated with voiding dysfunction [10]. In their study only 5 out of 38 had abnormal VCUG and KUB. From their study they strongly recommend VUDS to be considered in children with recurrent UTIs and a history of voiding dysfunction [10]. To address the current controversies in the additional value of UDS in children with NNLUTD, ICCS advocates for urodynamic testing in children with NNLUTD only if it will guide treatment plans and procedures [12].

There is controversy surrounding the method of bladder catheterization when performing a urodynamic examination. The concern regarding transurethral catheters is that it can affect urethral function and increase leak point pressure (LPP). However, several studies have demonstrated that the use of catheterization does not alter urethral function [22‐24]. The ICCS Standardization Report on Urodynamic Studies of the Lower Urinary Tract in Children recommends the use of either methods; however, risks should be weighed against benefit when the suprapubic route is used. In this study almost all (97.5%) urodynamic studies were performed with either a 6F or 7F double lumen transurethral catheters. Voiding phase is often assessed by performing a uroflow first and removal of the catheter after an invasive study, however this study did not determine the number of UDS where the voiding phase was assessed this way. The main reason for those performed using either Mitrofanoff (1.1%) or suprapubic catheter (1.4%) was because the patients were already using the technique for bladder emptying. The use of suprapubic catheterization is not a feasible option in a resource limited setting as it requires hospital admission with theatre time and monitoring space.

Although UDS usage has increased, concerns have been raised that the use of invasive urodynamic testing is not always justified in some patients. Only 5.0% of studies were reported as normal and this finding may reflect the appropriate use of UDS in children. This is comparable to Hoebeke et al. and Johnston et al. who reported 6% and 8% of normal studies respectively [5, 11]. Glazier et al. reported much higher incidence of normal studies when evaluating the utility of VUD in 42 children with UTI and voiding dysfunction [10]. Even though a significant number (430 of 727) of children were receiving more than on type of bladder treatment at first study, the study revealed low bladder compliance (278 of 727), DLPP > 30 cm H₂O (160 of 727), neurogenic detrusor overactivity (54 of 727) and DSD (26 of 727). This reflects the difficulties in treating some of these patients and that UDS is often warranted to facilitate more specific diagnoses and guide treatment. The higher incidence of low bladder compliance (420 of 820), in those with NLUTD represents the importance of UDS in all patient with suspected NLUTD to identify those at risk for problems. ICCS advocates early urodynamic profiling in these patients and follow-up studies to allow early intervention and decrease significant complications. In this study the incidence of VUR could only be determined after introduction of VUDS, from year 2017. VUR was detected in 54 out of 168 (32%) VUDS. This study did not differentiate whether VUR was primary or secondary.

The clinical significance of performing a urodynamic testing has been demonstrated in this study. The overall goal of treatment of children with LUTDs is to preserve upper tracts and ameliorate or delay progression to ESKD especially in a setting where dialysis and transplantation may not be easily available. From the literature, factors associated with upper tract damage are low bladder compliance, DSD, neurogenic detrusor overactivity (NDO) and DLPP > 40 cm H₂O. With the exception of NDO (p = 0.48), there was significant statistical improvement between the first study and follow-up study using low bladder compliance (p < 0.001), DLPP > 30 cm H₂O (p < 0.001) and DSD (p = 0.03). Based on this finding, the use of urodynamic examination in children with LUTDs has the potential to lower the incidence rate of renal replacement therapy.

The strength of this study is that it represents the largest number of invasive urodynamic studies in Sub-Saharan region. Another strength of this study is that it included a wide array of clinical indications and broader range of diagnosis. This study also included a diverse set of referring specialities. Nevertheless, this study is not without limitations. This was a single centre study but with large numbers. Other limitations relate to its retrospective design. Some UDS were excluded because of missing data and some studies may have been missed. Also, the incidence of DSD and VUR reported in this study may have been underestimated as they were periods where the centre was unable to perform electromyography and the use of VUDS started after year 2017.

In conclusion, this study has demonstrated an increased interest in the use of UDS in children. It has highlighted the difficulties in the management of children with LUTDs which may necessitate that multiple follow-up studies be carried to monitor response. The recommendation of early and frequent follow-up UDS for children with spinal dysraphism recommended by ICCS may not be feasible in a resource limited country. For Africa this may mean early start on CIC, prioritizing patients based on their risk for upper tract damage and effective application of bladder and stool diaries, KUB (pre- and post-void residual volume) ultrasonography and VCUG.