Differential Diagnosis

• Single most likely diagnosis
  • B. Cholecystolithiasis: This is the most likely diagnosis given the ultrasound findings of a hypoechoic structure with posterior acoustic shadowing within the gallbladder (GB), which is characteristic of gallstones. The absence of gallbladder wall thickening, pericholecystic fluid collection, and symptoms such as abdominal pain suggests that the condition is likely asymptomatic cholecystolithiasis.
• Other Likely diagnoses
  • A. Choledocholithiasis: Although less likely given the specific location of the finding within the GB, choledocholithiasis (stones in the common bile duct) could potentially present with similar ultrasound findings if a stone is lodged at the junction of the cystic duct and common bile duct. However, this would typically be associated with symptoms or laboratory findings indicative of biliary obstruction.
  • C. Chronic calculous cholecystitis: This condition involves chronic inflammation of the gallbladder due to the presence of gallstones. While it could explain the ultrasound findings, the absence of symptoms and specific signs of chronic inflammation makes it less likely than asymptomatic cholecystolithiasis.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • D. Acute calculous cholecystitis: Although the patient does not have symptoms of abdominal pain, it is crucial not to miss acute cholecystitis, as it can lead to severe complications such as gangrene, perforation, and sepsis. The absence of wall thickening and pericholecystic fluid on ultrasound does not entirely rule out early or mild cases.
• Rare diagnoses
  • Gallbladder polyps or tumors: While rare, these could potentially present as hypoechoic structures within the gallbladder. However, they would not typically cause posterior acoustic shadowing, which is more characteristic of stones.
  • Sludge or microlithiasis: These conditions involve the presence of small, often non-shadowing, particles within the gallbladder and might not fully explain the posterior acoustic shadowing seen in this case.