Biliary Microlithiasis

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Biliary Microlithiasis - Theories

Our Theory on How Foci Cause Medical Disorders

Foci rapidly free fall in bile after disturbance suggesting their heavy density compared to bile. Not commonly seen on routine gallbladder ultrasound because they do not shadow and blend in with the dependent gallbladder wall, slow rotation will not stir them up, the transducer is not positioned on the gallbladder immediately after rotation and they can be obscured by an inappropriate ultrasound technique.

Foci could obstruct in the cystic duct, pancreatic duct and ampulla resulting in clinical disorders.  It could be assumed that foci this small should pass through the cystic duct and ampulla without obstruction.  We feel foci could obstruct as a single or more often as a localized impacted mass of multiple foci within a duct.  The impacted mass could occur in the larger ampulla, whereas a single foci could obstruct in the smaller cystic duct and pancreatic ductule.  

Impaction by multiple foci forming a mass may occur for the following reasons.  Occasionally a linear debris like structure is seen falling as fast as foci assumed to be attached to the foci.  Foci may be lenticular or saucer shaped, especially if formed in a valve of Heister of the cystic duct.  The lenticular shape facilitates obstruction by the impaction of multiple foci.  (I noticed bulk almonds sliding down a plastic shute in the grocery store stopped sliding by piling up inappropriately against a small ledge due to their lenticular shape.  Round nuts would not stop in this way.)  Sharp edges, excessive numbers, a lenticular shape and debris attached to foci could all facilitate obstruction by the impaction of multiple foci.  Obstruction may be partial or complete and is usually temporary.  A sieve-like impacted mass would allow flow of bile through it as a partial obstruction. It may last for longer periods because pressure is balanced and does not disrupt the obstruction.  Partial obstructions in the ampulla, either intermittently or continuously, could occur for longer periods up to many years. 

We speculate that one foci or an accumulation of foci as an impacted mass, could partially or completely obstruct in the CBD ampulla, the pancreatic duct and ductules and the cystic duct.  A focal saccular dilatation in the ampulla would enhance the impaction of multiple foci.  If the pancreatic duct entered the ampulla at the dilatation it could result in pancreatitis.  A partial obstruction in the ampulla could last for varying periods of time due to a balanced pressure gradient in the CBD.  A complete or near complete ampullary obstruction would usually be quickly cleared by contractions of the CBD and gallbladder. This may result in pain but pain could occur for hours or days if the obstruction persists.

There is no obvious correlation between the number of foci visualized and clinical abnormalities.  We tend to see greater numbers in pancreatitis.  Perhaps endogastic ultrasound could define the anatomy of the ampulla to predict susceptibility to pancreatitis due to foci.