BACKGROUND: Cholelithiasis in neonates and infants has been rarely reported, but with the current widespread use of diagnostic abdominal ultrasonography more neonates may be found with gallstones. The clinical situations include symptomless cases with spontaneous resolution and relatively rare cases with serious complications due to choledocholithiasis.AIM: To determine the incidence, spontaneous course and the complications of cholelithiasis in neonates. A review on the various form of cholelithiasis in neonatal age has been also carried out.PATIENTS AND METHODS: Three hundred and thirty nine neonates were screened during 4 months (March - June 2005) by abdominal ultrasound (Aloka SSD-1400, sonde 7,5 MHz). There were 273 physiologic newborns (otherwise healthy newborns with no medical history of factors potentially predisposing to stones) and 66 pathologic neonates (pathologic course of perinatal periode). Abdominal ultrasonography was performed at the first 5 days of life (physiologic newborns) or as soon as possible (pathologic newborns). Neonates with the diagnosis of the echogenic material in the gallbladder were prospectively followed up in 1-month periods until this US finding was present.RESULTS: The presence of the echogenic material in the gallbladder were diagnosed in five physiologic newborns (1,8%, 3 girls and 2 boys). True gallstones with acoustic shadow, sludge-balls and sludge were diagnosed in one, three and one of them, respectively. The presence of the echogenic material in the gallbladder were also found in four pathologic newborns (6,1%, 2 girls and 2 boys). True gallstones, sludge-balls and sludge were diagnosed in two, one and one of them, respectively. No significant sex predominancy were found (5 girls and 4 boys). At follow-up the biliary stones in all five physiologic infants had spontaneously completely resolved at the age of 1 months with no symptoms. In three of four pathologic newborns this findings has reminded in the third month of theirs life. All children were asymptomatic from the biliary system. CONCLUSIONS: The present study suggests that idiopathic neonatal cholelithiasis seems to be more common phenomenon than previously suspected - our research showed an incidence of 0,36% of true gallstones and 1,8% of the presence of echogenic material in the gallbladder in physiologic newborns. There could be the maternal and delivery predisposing factors whose disappear after delivery and so the connatal gallstones often disappear spontaneously. The incidence of “pathologic” neonatal cholelithiasis related to the predisposing factors (prematurity, total parenteral nutrition, neonatal sepsis, dehydratation, furosemid therapy etc.) has been estimated also higher than expected - incidence of 3,0% of true gallstones and 6,1% of the presence of echogenic material in the gallbladder in pathologic newborns. Difference of incidence in physiologic vs. pathologic newborns confirm that predisposing factors plays an important role in the pathogenesis of neonatal cholelithiasis. The most frequent evolution is spontaneous resolution of the biliary echogenic images in absence of clinical manifestations. The complications are rare. Thus we conclude that the incidentally diagnosed neonatal cholelithiasis can be considered as a relatively common phenomenon, with good prognosis and rare complications. If it is asymptomatic, no treatment is needed except for abdominal sonography follow-up until this finding is present. In the symptomatic cases the therapy is to be chosen in each case in accordance with clinical features.