Unlike ultrasound (US), CT can also better visualize the gastrointestinal tract, including gastroduodenal abnormalities such as severe inflammation or perforation, colitis involving the hepatic flexure, and abnormalities of the adjacent osseous structures. Pancreatic masses and acute pancreatitis are similarly better evaluated. Contrast enhancement is an additional advantage that can aid in visualizing and characterizing enhancing hepatic, pancreatic, adrenal, and bowel lesions. CT without intravenous (IV) contrast can detect some features and complications of AC, such as gallbladder wall thickening, pericholecystic inflammation, gas formation, and hemorrhage. However, some important features that add confidence to the diagnosis such as wall enhancement and adjacent liver parenchymal hyperemia, one of the earlier findings in AC, cannot be detected without IV contrast [7]. CT without and with IV contrast is not often viewed as helpful in assessing patients admitted with right upper quadrant abdominal pain because the noncontrast portion does not add value and little additional information is gained by the routine addition of a noncontrast phase to a contrast-enhanced phase in this clinical setting [10]. CT with IV contrast is a useful tool for the assessment of hepatic pathology such as liver abscess (including the ones <5 mm) and metastatic disease. Furthermore, dual-phase contrast-enhanced CT can detect hemorrhage including active extravasation from liver tumors such as adenomas or hepatocellular carcinomas with accurate identification of the bleeding source. Similarly, severe inflammation of the gastroduodenal region, as well as of the pancreas, can be well detected and characterized on contrast-enhanced CT. If the clinical question only pertains to the presence or absence of bowel perforation, noncontrast CT alone may be enough for the assessment.
Right Upper Quadrant Pain. Unlike ultrasound (US), CT can also better visualize the gastrointestinal tract, including gastroduodenal abnormalities such as severe inflammation or perforation, colitis involving the hepatic flexure, and abnormalities of the adjacent osseous structures. Pancreatic masses and acute pancreatitis are similarly better evaluated. Contrast enhancement is an additional advantage that can aid in visualizing and characterizing enhancing hepatic, pancreatic, adrenal, and bowel lesions. CT without intravenous (IV) contrast can detect some features and complications of AC, such as gallbladder wall thickening, pericholecystic inflammation, gas formation, and hemorrhage. However, some important features that add confidence to the diagnosis such as wall enhancement and adjacent liver parenchymal hyperemia, one of the earlier findings in AC, cannot be detected without IV contrast [7]. CT without and with IV contrast is not often viewed as helpful in assessing patients admitted with right upper quadrant abdominal pain because the noncontrast portion does not add value and little additional information is gained by the routine addition of a noncontrast phase to a contrast-enhanced phase in this clinical setting [10]. CT with IV contrast is a useful tool for the assessment of hepatic pathology such as liver abscess (including the ones <5 mm) and metastatic disease. Furthermore, dual-phase contrast-enhanced CT can detect hemorrhage including active extravasation from liver tumors such as adenomas or hepatocellular carcinomas with accurate identification of the bleeding source. Similarly, severe inflammation of the gastroduodenal region, as well as of the pancreas, can be well detected and characterized on contrast-enhanced CT. If the clinical question only pertains to the presence or absence of bowel perforation, noncontrast CT alone may be enough for the assessment.