Figure 9. Flowchart for the investigation of postcholecystectomy pain.

Obstruction in some patients may result from paradoxical contraction of the sphincter of Oddi in response to CCK and may only be apparent on CCK-8 augmented scintigraphy. Since CCK-8 enhances bile formation, signs of obstruction will be more apparent during high flow bile states compared with the low rates of production in the interdigestive phase—analogous to the use of diuretic renography to diagnose urinary tract obstruction. CCK-8 may also reduce the intermittent emptying seen during fasting. A prolonged physiologic infusion of CCK-8 should yield the best results.

Biliary obstruction

High grade biliary obstruction results in elevated intrabiliary pressure which reduces bile formation by opposing secretion from the liver and, over time, results in dilatation of the biliary tree. Bile duct dilatation is the hallmark of obstruction on anatomic imaging studies. US can easily detect dilatation of the CBD but may have difficulty visualizing its distal portion because of interference by bowel gas. CT and MRI are less affected by bowel gas and may be able to identify the cause. Scintigraphy shows abnormal retention of radiotracer in the biliary tree, or if intrabiliary pressure exceeds secretion pressure of the liver, will show hepatic uptake with prolonged retention. The findings are independent of biliary dilatation and a diagnosis can be made during the first hours or days before the diagnosis can be made by anatomic imaging. Scintigraphy, however, can seldom demonstrate the precise cause and anatomic imaging is the initial procedure of choice regardless of the time of suspected onset of biliary obstruction.

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