Table 3. Imaging studies.

Type of study	Observation	Advantage	Disadvantages	Sensitivity/specificity
Ultrasonography	Contracted gallbladder; impacted cystic duct stones; common hepatic duct and intrahepatic biliary tree dilated above the site of obstruction; normal common bile duct size under the level of obstruction	Low cost; noninvasive	Inflammation and excess intestinal gas reduces quality	Sensitivity 8.3–57%; specificity 90.9–100%
Computed axial tomography	Gallbladder with gallstones; dilated cystic duct; liver enlarged lymph nodes or liver metastases (sign of malignancy); narrowing in the bile duct without extrinsic mass; dilated common hepatic duct	Exclusion of malignancy	Nonspecific signs; periductal inflammation misinterpreted as gallbladder cancer	42–50% sensitivity
Endoscopic retrograde cholangio-pancreatography	Compression of the common hepatic duct; cholecystocholedochal fistula; gallstone impacted in the neck of the gallbladder or cystic duct; presence of ampullary duodenal disease, or pancreatic; adhesions between the gallbladder and the common hepatic duct, in the Calot triangle	Method of choice; assess and clean the biliary ductal anatomy; differentiate benign or malignant stricture; allows therapeutic intervention (biopsy, recovery calculation or stenting)	Invasive procedure; you cannot display the common bile duct (obstruction of the common hepatic duct); it presents complications (pancreatitis, sepsis) at 23%	Sensitivity of 50–100%
Magnetic resonance cholangio-pancreatography	Extrinsic narrowing of the common hepatic duct; gallstone in the cystic duct; dilated common hepatic duct and intrahepatic; extension of the inflammatory process and degree of obstruction; rule out other causes of bile duct obstruction	Avoids complications; non-invasive; procedure prior to endoscopic retrograde cholangio-pancreatography choice; corroborating malignancy	Unable to confirm the presence of fistulas; it does not allow therapeutic interventions	Sensitivity 77.8–100%; specificity 93.5%
Intraoperative diagnosis	Contracted gallbladder with distorted anatomy; gallbladder dilated with thick walls; gallstones, impacted in the neck of the gallbladder or infundibulum; Calot triangle obliterated or fibrotic mass; adhesions in the subhepatic space, or the common hepatic duct in the area of the Calot triangle	More than 50% of diagnoses	–	Sensitivity and specificity not reported