Unusual ivory-white gallstones identified during indocyanine green fluorescence-guided laparoscopic cholecystectomy: a rare case report.

Ivory-white gallstones represent a rare morphological variant of cholelithiasis, differing from typical cholesterol stones, black pigment stones, or brown pigment stones. Their unusual appearance and poorly understood pathogenesis make them an infrequently reported finding in clinical practice. This study presents a case of ivory-white gallstones discovered during indocyanine green (ICG) fluorescence-guided laparoscopic cholecystectomy. A 70-years-old male presented with a 6-years history of intermittent right upper quadrant pain, clinically diagnosed as chronic symptomatic cholecystitis. Preoperative Computed Tomography (CT) revealed unusually hyperdense foci (500-1200 HU) within the gallbladder, suggesting high calcium content. The patient underwent indocyanine green (ICG) fluorescence-guided laparoscopic cholecystectomy. Gross examination revealed multiple distinctive ivory-white, brittle gallstones, with the largest measuring 2.5 cm. An intriguing "gel-to-solid" phase transition was observed: opalescent, mucoid-like concretions within the gallbladder cavity rapidly hardened into solid, chalky granules within minutes of exposure. Morphologically, the stones exhibited a homogeneous white interior without layering. While the absence of formal compositional analysis limits definitive mechanistic conclusions, the macroscopic appearance and high CT density suggest a complex interplay between cholesterol supersaturation and significant calcium deposition within a chronic inflammatory environment. This case highlights a rare morphological variant of cholelithiasis. Although such atypical morphology does not alter standard surgical management, it provides critical insights into the diverse physical chemistry of gallstone formation.