Biliary sludge can occur when taking medicines (oral contraceptives, cephalosporins, octreotide, furosemide, clofibrate, morphine, calcium preparations, etc.). In particular, 30–40 % of ceftriaxone, which is widely used in pediatric inpatient practice, is excreted with bile, 5–15 % of all side effects of the drug are due to biliary sludge. The mechanism of ceftriaxone-associated biliary sludge is due to the fact that ceftriaxone competes with bilirubin for albumin, which induces an increase in unconjugated bilirubin in the blood. The drug enters the bile in the form of a divalent anion, binds to calcium in ceftriaxone-calcium complexes with inclusions of cholesterol monohydrate crystals and bilirubinate granules. In patients taking cephalosporins, when complaints from the gastrointestinal tract appear, ultrasound screening is mandatory. Children with a family history of gallstone disease and risk factors should undergo ultrasound screening on the 10th day and 1 month after treatment with cephalosporins, even in the absence of complaints. The administration of ursodeoxycholic acid leads to a significant regression of clinical symptoms of biliary sludge and objective ultrasound signs in 2/3 of children after 2 months.