biliary microlithiasis biliary microlithiasis biliary microlithiasis refers to the creation of small gallstones less than 3 mm in diameter in the biliary duct or gallbladder. it has been suggested as a cause of postcholecystectomy syndrome, or pcs, the symptoms of which include: upset stomach, nausea, and vomiting. gas, bloating, and diarrhea. persistent pain in the upper right abdomen. diagnostics biliary microlithiasis may be detectable by ultrasound using a rapid patient rotation ultrasound protocol analysis of biliary sludge obtained through endoscopic retrograde cholangiopancreatography (ercp) treatment oral ursodeoxycholic acid can be used to dissolve these crystals.