A pilot study assessing average detrusor pressure garnered from area under a urodynamic curve: Evaluation of clinical...

The management of neurogenic bladder mostly relies on urodynamic studies; however, several studies have shown low interobserver reproducibility. The aim of this study was to evaluate if a new objective cystometric parameter was superior to other cystometric measures.

A new parameter (pressure adjusted area under curve ratio, PAUC) was formulated from the ratio of area under the cystometry curve to a DLPP-adjusted total area (A_T). A_T was figured from a rectangle designed on the cystometrogram curve with a fixed height of 200 cmH₂O and a width defined by the filling phase (figure). Two different estimated pressure measures derived from this (upper mean static pressure, UMSP and theoretical end filling pressure TEFP) were then calculated. Medical records of myelomeningocele patients with ultrasonography and renal scintigraphy performed at the time of urodynamics (with an interval of >5 years) were reviewed. Hydronephrosis and new scars in scintigraphy were used as the outcome measures.

The study group consisted of 115 subjects with a median age of 4 (0-23) years at the time of the first urodynamic study. The median follow-up was 6 (5-14) years. PAUC and its derivatives (UMSP and TEFP) had the best discriminative power in predicting high grade hydronephrosis (0.830, 95% CI:0.732-0.927, p < 0.001), worsening in hydronephrosis (0.827, 95% CI:0.723-0.931, p < 0.001), and new scar formation (0.704, 95% CI: 0.576-0.832, p = 0.002). PAUC>0.1 significantly correlated with urinary tract dilatation (p < 0.001) and new scar formation (p = 0.002). In the multivariate analysis, our three parameters and having scars at admission were the only independent risk factors for new scars (p = 0.001 and p = 0.002, respectively) and worsening in hydronephrosis (p < 0.001 and p = 0.001, respectively).

Our results show that our three parameters derived from area under the urodynamic curve are more reliable than other urodynamic measures. Their major theoretical advantage is to incorporate all the pressure during filling phase giving a more accurate picture of what the intravesical pressure milleu is. Using these measures, we demonstrated their superiority in predicting clinical outcomes. Major limitations of this study are the retrospectively collected data and lack of longitudinal follow-up starting from infancy in each patient.

Our new parameters (PAUC, UMSP and TEFP) which incorporate the impact of entire filling phase pressure changes in the analysis, may be useful tools to identify those patients who are under the risk of kidney damage with neurogenic lower urinary tract dysfunction.