Cholelithiasis

1. Pathogenesis:

• May occur when cholesterol levels are high. Normally, bile salts and lecithin are sufficient to keep the cholesterol soluble.
   
• Approximately 80% of stones are lucent cholesterol and 20% contain enough calcium to be detected on radiograph.
   
• Gallstones are more common in women and in patients with pancreatitis, cirrhosis, diabetes, Crohn's disease, hyperparathyroidism, and hemolytic anemia.
   
• Stones are freely moveable and may float in the gallbladder depending on their density.
   

2. Radiographic findings:

• U/S: all gallstones will show a bright intraluminal echo and cast a posterior shadow when imaged under the appropriate conditions and with the correct transducer settings.



• Small stones (< 5mm) will likely have to be imaged with a high frequency transducer to observe shadowing.
   
• In approximately 20% of cases, the gallbladder will be completely filled with stones. In such a case, the gallbladder will demonstrate a bright echo with posterior shadowing.