Ultrasound bladder measurements in patients with primary nocturnal enuresis: a urodynamic and treatment outcome correlation.

Purpose: Accurate assessment of bladder dysfunction associated with voiding dysfunctions often necessitates invasive urodynamic (UD) studies. We evaluate the use of a special ultrasound (US) protocol for the assessment of bladder dysfunction compared with urodynamic findings, and for prediction of treatment outcome in children with primary nocturnal enuresis (PNE).

Materials And Methods: US measurements were performed on 514 children 5 to 18 years old (mean age 11.2) with PNE, and compared with those of 339 normal age matched children. A US protocol was specially designed for the evaluation of bladder parameters using bladder volume and wall thickness index (BVWI %), and expected percentage bladder volume index for kidney volume. Of the enuretic children 218 had severe enuretic symptoms with more than 3 wet nights a week. They underwent urodynamic studies for detailed assessment of any underlying bladder dysfunction. A standard 4-week course of desmopressin was given to these children after the US and UD studies. The US bladder parameters were then correlated with the UD findings and treatment response to desmopressin.

Results: Comparing the BVWI in normal and enuretic children in correlation with functional bladder capacities we were able to delineate bladder wall thickness and capacity as BVWI less than 70-small capacity bladder with thick wall, BVWI 70 to 130-normal bladder capacity with normal wall thickness and BVWI greater than 130-large bladder capacity with thin wall. There were statistically significant correlations between BVWI and treatment response. In addition, there was a high predictive value of normal bladder function with a normal BVWI. Patients with good response to treatment had normal BVWI, whereas poor response to treatment was significantly associated with pathological bladder conditions, that is small bladder capacity with thick bladder wall or large bladder capacity with thin bladder wall (p <0.0001). Of note, abnormalities detected by UD correlated well with bladder abnormalities measured by US.

Conclusions: PNE comprises a diverse spectrum of conditions resulting in a mismatch of nocturnal urine production in excess of nocturnal functional bladder capacity, and underlying bladder dysfunction has an important role in the pathophysiology especially in refractory cases. This US protocol can provide useful predictive clues, which may be helpful to differentiate treatment subtypes, guide clinical management and minimize the need for invasive urodynamic studies.