Hypothesis / aims of study
Invasive urodynamic studies (UDS) can be associated with complications.
There is little in the literature describing the adverse events (AEs) encountered when performing UDS in children. To our knowledge, this is the first work aiming to assess AEs during paediatric UDS.
Study design, materials and methods
A retrospective, single-centre review of paediatric invasive UDS between January 2020-March 2022.
Data extraction was carried out from an excel database completed for audit purposes immediately after each study. Studies are performed according to ICCS, ICS, UKCS guidelines. All VUDs commenced in the supine position and the patient was moved to standing position, if able to stand unsupported. Cystometry was carried out supine or seated.
Patient demographics, urodynamic investigation (cystometry or VUD), diagnostic category, method of catheterisation (urethral, suprapubic, or in-situ urinary drainage) and type of associated sedation if required (general anaesthesia or Entonox), and AEs were reviewed. AEs were categorised into patient-, investigation- and catheter-related.
Results
A total of 602 studies (566 VUD, 36 cystometry) were completed. Median age at study date: 9 years (2 months-18 years). Males: 307 (61%). The underlying pathology was neurogenic (37%), anatomical (37%), functional (22%) and normal (4%).
Transurethral catheterization was used in 70% and suprapubic catheter (SPC) in 21%. The remainder were catheterised via mitrofanoff, vesicostomy, ureterostomy or mic-key button. Anaesthesia or sedation for catheter insertion was not required for 69%, 25% had general anaesthesia (including all SPC) and 6% needed Entonox.
The complication section of the database was completed in 503 (84%) study reports. 84 AEs were documented in 71 (14%) studies with 21 (4.2 %) studies experiencing more than one AE. See Table 1. 499 (99%) studies were completed. Studies abandoned: 2 due to extravasation, one large bladder clot and one fainting patient.
Patient-related AEs (8.2%) include voiding failure, patient anxiety, dizziness and fainting. Voiding failure (4.4%) was the most common AE, in- part related to patient anxiety (2.6%). Voiding failure occurred in 13% of patients with SPC and 2% with urethral catheter. Five patients (1%) felt dizzy while one fainted despite supportive measures.
Investigation-related AEs (8.6%) include failure to answer UDS question, unreliable traces and suspected high radiation dose. UDS question was not answered in 2 (0.4%) studies and partially answered in 19 (3.8%) studies due to voiding phase absence. Unreliable traces encountered in 11 (2.2%) studies due to inaccurate pressure detection by catheters. A single case of suspected high radiation dose exposure was investigated in a 125 kg, 169 cm 11-year-old girl. Following formal safety review the dose was within the local dose reference levels (LDRL) for adults in keeping with her auxology and pubertal status.
Catheter-related AEs include difficult catheterisation in 2 (0.4%) and catheter displacement in 5 (1%) patients with transurethral catheterisation. SPC-related AEs include extravasation in 2 patients (0.2%) and a large bladder clot in one patient (0.2%).
There was a higher prevalence of AEs within the anatomical group (24%) relative to the functional (13%) and neurogenic (4%) cohorts. Among males, AE occurred in 17% of cases, contrasting with 10% among females. The incidence of AE was similar between SPC (7%) and urethral lines (6%). When stratified by age, AE were most observed in the 1–5-year-old age group (18%), followed by the 5-12 years group (15%), and >12 years group (13%), with the <1-year-old group demonstrating the lowest incidence (8.5%).
Interpretation of results
Nearly one in seven children (14%) experienced an AE during UDS, however, most AEs are categorised as mild with none experiencing anything worse than Grade 1 according to the Common Terminology Criteria for Adverse Events (CTCAE) grading system.(1)
Although efforts are made to establish a natural testing environment with pleasant diversion (DVD, toys, music etc), the urodynamic setting and invasive nature remains somewhat artificial. Numerous children experience varying degrees of apprehension potentially affecting test performance and outcomes. This is despite careful explanation and description to the family and child beforehand and if necessary, the help of a play specialist both for preparation and presence during the study to try to mitigate anxiety, fear, and embarrassment.
Our study reveals a higher incidence of voiding failure with SPC compared to urethral catheterization. Contrary to some literature(2), our clinical experience suggests that urethral catheters may affect voiding and bladder outlet characteristics despite using a double-lumen 6frg catheter. The use of SPC is thus favoured to answer voiding and bladder outlet questions. In our unit, this predominantly affects boys with posterior urethral valves (PUV) and we suspect that voiding failure with SPC in-situ is linked to the necessity of initiating and sustaining voiding through abdominal straining, resulting in discomfort and rendering voiding unfeasible. Pre-UDS uroflowmetry with abdominal and pelvic floor EMG may point towards urethral catheterisation in these boys and obviate this complication. Apart from voiding failure, other AEs incidence in both groups was nearly similar.
Inaccurate pressure detection and catheter displacement can occur in any urodynamic setting particularly with restless or very active children necessitating re-catheterisation and possible re-admission and sedation. Accurate p-abd can be challenging in neurogenic cases with poor anal sphincter tone. This requires experienced and tailored staff training, and regular performance evaluations.
In paediatric patients complex congenital anatomical anomalies, for example anorectal malformations and PUV, can contribute to failed urinary catheterization attempts. Difficult catheterization can be anticipated and properly addressed by understanding patient-reported symptoms, obtaining a good urological history, and a thorough physical examination. Experienced catheter technique is equally important. Extravasation and bladder clots with SPC have previously been reported by our group (3); in this cohort both complications were managed with a period of drainage and delayed UDS using the same SPC.
In our unit, fluoroscopy is usually used with urodynamics (videourodynamics). To minimize the risk of radiation exposure, paediatric fluoroscopic screening recommendations are followed with very small doses of radiation and short fluoroscopy time. Radiation dose is monitored throughout the study and checked against the appropriate levels. Suspected incidents are reported and investigated.
Our study is limited to short-term AEs from invasive urodynamics and is not accurate for any AEs occurring in the mid- to long- term. We are aware of one PUV patient reporting pyelonephritis requiring admission five days after UDS via SPC (antibiotics given during GA) with no evidence of VUR during the study but incomplete bladder emptying. We do not routinely administer prophylactic antibiotics for UDS but do so in high-risk cases. No study is commenced in the presence of a possible UTI.
Our study is limited by incomplete AE recording, and it is possible that a bias existed towards completing the audit database when complications arose, potentially inflating the results.
The increasing use of urodynamics in children as part of early and proactive management of bladder dysfunction, in the absence of adequate data about AEs calls for more research to better define an evidence-based standard of care.