Surgeon has kindly answered your question in his comments below and I agree with his assessment.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
a stone in the bile duct has more potential danger than stones in the gallbladder, specifically pancreatitis and/or infection in the bile duct system. A 5 mm stone could indeed pass on its own; it's not possible to say with certainty. The fact is that the relative risk of the surgery was higher than that of ERCP. Complications can happen with any procedure, but in general ERCP is quite safe and it considered the most effective way to treat a bile duct stone. Alternatives include doing nothing in the hopes it will pass (but it can be hard to tell if it has, since the best way to image the duct is ERCP -- sonogram, for example, may or may not find a stone that's there); stones can be extracted by passing a wire through the liver, but it's not really safer than ERCP. And stone-dissolving pills can sometimes work. Finally, lithotripsy (smashing the stone with sonic waves) has been done for bile duct stones. Again, it's not free of side effects and risks. Without question, my approach to stones in the bile duct that couldn't be removed at operation is to have them removed by ERCP. Check out the list of possible complications from the surgery and anesthesia she already had: If you weren't terrified of that, you certainly shouldn't be terrified of ERCP.
I had ERCP twice following gallbladder removal and had pancreatitis, liver function damage and severe jaundice. I was sick for 5 months. I'm much younger, 52 but have to say that the pain from the stone was worse than the gall bladder pain pre-surgery. My ERCP was delayed for several days, not my choice and consequently my common bile duct became inflamed which caused bigger problems
A related discussion, bile duct stone
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I'm a 34 yr old who had the ercp 4 yrs ago and the pancreatitis was the problem and now I have a stone in my common bile duct but they don't want to do the ercp what is next?
A related discussion, bile duct was started.