Gallbladder perforation in photon counting CT: A case report.

A 74-year-old male presented to the emergency department with a 5-day history of abdominal pain and fever. Laboratory tests suggested infection and biliary obstruction. Contrast photon-counting computed tomography (PCCT) imaging revealed gallstones, acute cholecystitis, gallbladder perforation, and dilation of the upper segment of the common bile duct, with a suspicion of a potential common bile duct stone (CBDS) that was not visualized. When the energy level was adjusted to 120 keV during postprocessing, a tiny, high-density nodule in the common bile duct became visible. It was further enhanced using a pseudo-colored gallstone template. Surgical exploration confirmed the presence of CBDS. CBDS is often associated with complications such as biliary obstruction, cholangitis, and pancreatitis. In this case, identifying a tiny CBDS after initial contrast imaging suggested that CBDS may have been the underlying cause of the gallbladder perforation. PCCT's multi-energy capabilities played a crucial role in improving diagnostic accuracy and provided clinical insights into the possible cause of the perforation. This case demonstrates the importance of PCCT in diagnosing tiny CBDS, which may change the clinical understanding of gallbladder perforation etiology.