Ninety-five percent of patients with AC have gallstones, but the sensitivity of CT for the detection of these stones is only approximately 75%. Calcium-containing stones tend to be well seen; however, cholesterol stones may be isoattenuating or hypoattenuating compared with the attenuation of bile, making their detection difficult [29]. Right Upper Quadrant Pain Variant 2: Right upper quadrant pain. Suspected biliary disease. Initial imaging. CT Abdomen Although it has not been advocated as a primary imaging examination for acute right upper quadrant pain, CT can confirm or refute the diagnosis of AC in equivocal cases based on US or scintigraphy, with a negative predictive value approaching 90% [30]. It is usually most appropriate to perform this examination after a US and/or cholescintigraphy. CT may reveal such complications as gangrene, gas formation, intraluminal hemorrhage, and perforation [15-17,30-35]. Furthermore, CT has been advocated as a useful modality in preoperative planning, with the absence of gallbladder wall enhancement or presence of a stone within the infundibulum associated with a higher rate of conversion from laparoscopic to open cholecystectomy. The CT findings in AC are similar to those encountered by US [7] with the exception of gallstones, which may not be detected by CT. Other potential findings include adjacent liver parenchymal hyperemia, which can only be assessed if IV contrast is administered. Abnormal gallbladder wall enhancement can be seen in more advanced cases, as well as if IV contrast is employed [7]. Of note, the sensitivity for the detection of gallstones on CT is only approximately 75% and is dependent on differing density of the stone relative to bile [7]. CT is usually preferred over MRI, largely because of its speed [30].
Right Upper Quadrant Pain. Ninety-five percent of patients with AC have gallstones, but the sensitivity of CT for the detection of these stones is only approximately 75%. Calcium-containing stones tend to be well seen; however, cholesterol stones may be isoattenuating or hypoattenuating compared with the attenuation of bile, making their detection difficult [29]. Right Upper Quadrant Pain Variant 2: Right upper quadrant pain. Suspected biliary disease. Initial imaging. CT Abdomen Although it has not been advocated as a primary imaging examination for acute right upper quadrant pain, CT can confirm or refute the diagnosis of AC in equivocal cases based on US or scintigraphy, with a negative predictive value approaching 90% [30]. It is usually most appropriate to perform this examination after a US and/or cholescintigraphy. CT may reveal such complications as gangrene, gas formation, intraluminal hemorrhage, and perforation [15-17,30-35]. Furthermore, CT has been advocated as a useful modality in preoperative planning, with the absence of gallbladder wall enhancement or presence of a stone within the infundibulum associated with a higher rate of conversion from laparoscopic to open cholecystectomy. The CT findings in AC are similar to those encountered by US [7] with the exception of gallstones, which may not be detected by CT. Other potential findings include adjacent liver parenchymal hyperemia, which can only be assessed if IV contrast is administered. Abnormal gallbladder wall enhancement can be seen in more advanced cases, as well as if IV contrast is employed [7]. Of note, the sensitivity for the detection of gallstones on CT is only approximately 75% and is dependent on differing density of the stone relative to bile [7]. CT is usually preferred over MRI, largely because of its speed [30].