Biliary pseudolithiasis

Biliary pseudolithiasis is an unusual complication of ceftriaxone where the drug complexes with calcium and mimics gallstones.[1][2] It is reversed when ceftriaxone administration is stopped.[2] It was first described in 1988 by Schaad et al. as "reversible ceftriaxone-associated biliary pseudolithiasis".[2][3] Ceftriaxone has been frequently associated with biliary sludge or biliary pseudolithiasis in subsequent reports.[3] Ceftriaxone is excreted primarily through the urine, but also through the bile, up to 40% of its excretion, with concentrations in the bile 20-150 times higher than in the serum.[3][4] It forms a calcium salt in the gallbladder, which can exceed its solubility and create precipitates that resemble gallstones on ultrasonography.[3] The incidence of pseudolithiasis in children treated with ceftriaxone is up to 25%, but most patients are asymptomatic.[3][4] Risk factors for biliary pseudolithiasis include age greater than 24 months, gram-negative sepsis, high doses of ceftriaxone, hypercalcemia, surgery, and decreased bile flow/increased ceftriaxone excretion in bile.[3][4][5] Conservative management with serial ultrasounds is recommended until the "stones" completely resolve.[3] If associated with ceftriaxone, it resolves on average about 2 weeks after the ceftriaxone is stopped.[4]

Biliary pseudolithiasis
Biliary pseudolithiasis as seen on ultrasonography. The gallbladder contains gallstone mimics resulting from ceftriaxone therapy.