Is there any relationship between hyperbilirubinemia and pelvicaliceal dilatation in newborn babies?

A recent study reported association of high bilirubin concentrations with decrease in basal vesical tonicity and relaxation of pre-contracted ureteral and vesical smooth muscles in vitro, and authors discussed that recovery of antenatal hydronephrosis might partly be associated with decreased bladder resistance to the urine flow due to hyperbilirubinemia. We aimed to investigate whether any relationship between serum bilirubin levels and antero-posterior renal pelvic diameters or pelvicaliceal dilatations exist during newborn period. Neonates with hyperbilirubinemia [group 1] and healthy neonates [group 2] were randomly selected to the study. Capillary blood samples were used to measure micro-bilirubin. Urinary system ultrasound [US] was performed in both groups by an experienced radiologist. Group 1 [31 neonates, 16 males, 15 females] and group 2 [22 neonates, 11 males, 11 females] were identical by means of postnatal age, gender and weight [P>0.05]. Mean serum bilirubin levels were 11.1 +/- 3.1 mg/dl and 1.4 +/- 0.2 mg/dl in group 1 and 2, respectively. Renal length and renal pelvis antero-posterior [AP] diameters were not different between study groups. Pelvis AP diameters of right kidney were 2.110.7 mm in group 1 and 1.9 +/- 0.7 mm in group 2, and of left kidney were 2.4 +/- 0.8 mm in group 1 and 2.310.6 mm in group 2. There was no correlation between bilirubin levels and renal length and renal pelvis AP diameters [P>0.05]. In this study we were not able to demonstrate any relationship between serum bilirubin levels and renal pelvic diameters and pelvicaliceal dilatation in hyperbilirubinemic neonates. So, it is thought that hyperbilirubinemia might not have a direct effect on outcome of the pelvicaliceal dilatation