Dynamic ultrasound study on urinary bladder in infants with antenatally detected fetal hydronephrosis.

To evaluate bladder function in infants with antenatally diagnosed hydronephrosis (ANH) using dynamic ultrasound protocol. Forty consecutive male infants (mean, 0.25 y) with ANH and 33 age-matched normal controls (mean, 0.49 y) were recruited. Anteroposterior (AP) diameter of renal pelvis (RP) and hydronephrosis index [HI = anteroposterior diameter of RP of kidney divided by urinary bladder volume (BV)] were calculated. Maximum BV (MaxBV) was determined just before voiding. Residual volume (RV) and bladder wall thickness (BWT) were measured after spontaneous voiding. Thirty-one infants (77.5%) showed persistently dilated RP postnatally in which 12 (39%) showed significantly high HI. In general, ANH infants had smaller MaxBV (30.71 versus 52.45 mL), larger residual volume (2.47 versus 1.93 mL), and larger BWT (4.4 versus 3.7 mm) than normal (p < 0.05, Mann-Whitney test). Infants with abnormally high HI had significantly more disturbed bladder parameters [smaller MaxBV (23.33 versus 33.49 mL) and larger BWT (4.67 versus 3.79 mm)] than the normal HI group (p < 0.05, Mann-Whitney test). Abnormal functional bladder parameters were evident in ANH infants. We postulated that immature function in the pelviureteric junction was associated with bladder dysfunction in these infants. Dynamic ultrasound protocol might help to understand the underlying pathophysiology of urinary system in ANH infants.