| Discussion: |
Stones in the CBD usually originate in the Gb and migrate distally. Calculi can obstruct anywhere in the biliary duct, but most often cause obstruction at the level of the pancreatic head. Data are lacking in children, but in adults, the sensitivity of sonography for detecting choledocholithiasis is between 55% and 80%. The sensitivity is lower for stones distally versus the proximal duct. A distal impacted calculus is more difficult to detect because of adjacent or overlying bowel gas and because the calculus is surrounded by the echogenic pancreatic head.
At sonography, bile duct calculi are seen as echogenic foci, usually with acoustic shadowing. About 10% of duct stones in adults do not cause acoustic shadows. As many as 25% of adults with bile duct stones have normal (non-dilated) ducts.
The common causes of cholelithiasis in older children and adolescents include cystic fibrosis, malabsorption, total parenteral nutrition, liver disease, Crohn's disease, bowel resection, and hemolytic anemia. Less commonly, gallstones have been associated with the use of drugs (particularly, ceftriaxone and cyclosporine) and metachromatic leukodystrophy.
Gallstones may be composed of cholesterol, pigment (calcium bilirubinate) or calcium carbonate. About 90% of gallstones have a mixed composition. Pure cholesterol stones represent 10% of all stones, and pure calcium carbonate stones are rare. Pigment stones account for a higher percentage of stones in prepubertal children, whereas cholesterol stones are relatively more common in adolescents and adults. Unless symptomatic, gallstones do not require surgical intervention and often resolve without treatment.
* Special thanks to John McFadden MD, Radiologist, Lutheran General Hospital, Park Ridge, Illinois and Marianna Desmond, Sonography Instructor, Triton Community College, River Grove, Illinois.