Nuances and Pitfalls in Pediatric Urodynamics: Perfecting Imperfection.

Urodynamics plays a fundamental role in the evaluation and management of many complex pediatric cases. Investigation and treatment of our neuropathic bladder population requires a diligent, comprehensive approach for optimization of continence potential and prevention of renal deterioration. Although the argument can be made that pediatric patients’ age, cognitive abilities and communication limitations make urodynamics more relevant, they also can limit interpretability. Therefore, a great deal of effort has been accumulated to maximize accuracy and standardize applications and interpretations. The goals of caring for a child with a neuropathic bladder are simple, but achieving them can be complex. The pediatric urologist is tasked with 1) optimizing renal health and minimizing risk of deterioration, 2) promoting urinary continence and 3) ensuring long-term bladder health. This field was revolutionized by McGuire et al with the declaration that 40 cmH2O bladder pressure was associated with hydronephrosis and renal insufficiency. The introduction by Lapides et al of clean intermittent catheterization brought this patient population closer to “normal emptying” and further decreased morbidity. With the advent and progression of bladder relaxant medication, continence could be achieved and may be expected. Finally, the refinement of bladder augmentation with catheterizable channels has meant that even patients with the most hostile bladders can expect good function and improved quality of life. However, each of these steps requires a significant investment in patient and family time, and risks significant morbidity. Therefore, it is paramount that progression through our clinical algorithms occurs in an orderly, thoughtful and evidence-based fashion. The 3 tools we rely on the most are history, ultrasound and urodynamics. The urinary history is relatively simple with respect to infections, continence and negative effects of the current treatment regimen. The primary challenge is ascertaining compliance with catheterization and medication regimens. Ultrasound is invaluable and is very good at broadly categorizing patients into low risk (good emptying and no hydronephrosis) and high risk (bilateral hydroureteronephrosis and distended bladder). Therefore, we depend on urodynamics to help guide us through the middle ground, with the patient who is mostly continent, who has not started to catheterize or who has started to show a little hydronephrosis. Thus, we rely on urodynamics to provide us with reliable, reproducible and dependable results. However, many significant variables prevent us from being 100% confident in each test we review, and, therefore, myriad attempts have been made to improve the accuracy and predictive value of the study. The International Children’s Continence Society has been pivotal in standardization of testing vocabulary and protocols, which has been very advantageous in advancing clinical care and facilitating research. We must all know exactly what each study is reporting and be confident that the results will translate to our populations. In this issue of The Journal (page 577) Ergun et al highlight another good example of both the efforts put forth to improve and the difficulties in reproducing the examination. The authors found that repeating the filling cycle 3 times did confirm some accuracies and did show discrepancies. The maximal cystometric capacity and the presence of detrusor overactivity (although not quantified) remained consistent, but detrusor leak point pressure (dLPP) decreased with repetition. Of the children whose initial studies demonstrated dLPP above 40 cmH2O 33% had this decrease to less than 40 cmH2O. The authors attribute this to the variability in viscoelastic properties of the bladder. Their clinical application of these findings was to assume the initial (worst) dLPP was most accurate and would be the basis of changing treatment plans. This is intuitive if the primary goal is to protect the kidneys from elevated pressures, and if 40 cmH2O is the threshold for intervention. Many other authors and institutions have reported similar variability. Dudley et al have published a series of increasingly sophisticated articles exploring interrater reliability, and concluded that only moderate