when a stone obstructs the gallbladder ( gb ) neck or cystic duct , an acute inflammation process can occur . the prevalence of cholelithiasis , presence of stones in the gb , is about 1015% in the general population . among those with cholilithiasis , overall , acute cholecystitis will develop in up to 30% of patients with cholilithiasis . however , acute cholecystitis develops in men more frequently than would be expected from the relative prevalence of gallstones ( about half that in women ) , and cholecystitis tends to be more severe in men . in patients with diabetes , acute cholecystitis seems to develop more frequently than in patients without diabetes , and such patients are more likely to have complications of acute cholecystitis when it occurs . the symptoms include right upper quadrant abdominal pain , fever , nausea and vomiting , loss of appetite , and mild jaundice . the clinical symptoms and laboratory findings for acute cholecystitis are nonspecific and they can also be found in other conditions . in elderly patients , delays in diagnosis are common because physical examination and laboratory indexes may be normal . a 69-year old male , who underwent ascending aortic aneurysm repair with no past medical history of alcohol or tobacco abuse , hypertension , diabetes mellitus , obesity and peptic ulcer disease on day twelve postoperatively developed low - grade fever and leukocytosis . his white blood cell count was 16.60 ( normal 4.810.8 billion cells / l ) . a chest computed tomography ( ct ) revealed a periaortic hematoma which represents a postsurgical change from aortic aneurysm repair , and a small pericardial effusion . an ultrasound ( us ) examination of the abdomen was done and it showed cholelithiasis and gb sludge without evidence of cholecystitis . after this , a positron emission tomography ( pet)/ct was ordered to look for any metabolic activity in the periaortic hematoma to rule out infection . the fluorodeoxyglucose ( fdg)-pet / ct examination found no abnormal fdg activity in the periaortic hematoma to indicate infection . there was an incidental finding of intensely increased fdg activity within the distended gb wall , with associated mild pericholecystic fat stranding and stones in the gb neck [ figure 1 ] . he underwent cholecystectomy and pathology confirmed the diagnosis as acute cholecystitis . a 69-year - old male developed low - grade fevers and leukocytosis , after ascending aortic aneurysm repair with aortic valve replacement . ( a ) fluorodeoxyglucose - positron emission tomography / computed tomography maximum intensity projection image shows no signs of infection around the aorta but increased metabolic activity around the gallbladder ( arrow ) . ( b ) axial view computed tomography image shows a distended gallbladder with mild pericholecystic fat stranding ( arrow ) . ( c ) fluorodeoxyglucose positron emission tomography image and ( d ) hybrid fluorodeoxyglucose - positron emission tomography / computed tomography , axial views , show increased tracer uptake in the wall of the gallbladder , with no uptake in the lumen ( arrows ) . to the best of our knowledge , there are only two prior reports in the english language literature that mention the use of fdg - pet / ct to image acute calculous cholecystitis . our paper is unique ; in that , we did not intend to diagnose acute cholecystitis with fdg - pet / ct . the abdominal us is often the first step in the workup for suspected acute cholecystitis because it is safe , widely available , and inexpensive . stogryn et al . , reported that us has a low negative predictive value and it can underdiagnose acute cholecystitis . in the current case , the us examination found cholilithiasis but no signs of cholecystitis . a prospective study by bingener et al . , found that the sensitivity and specificity of us were 54% and 67% , respectively . the same study reported that the us 's ability to predict acute cholecystitis in patients with clinical symptoms appears limited . age , diabetes mellitus , and pain medications can potentially mask a sonographic murphy sign . our patient was a 69-year - old diabetic who was on pain medications after the surgery . with us , a gallstone may or may not be visualized within the gb neck or cystic duct . the patient must be in the prone or left lateral decubitus position , to better visualize a stone impacted in the gb neck or cystic duct . radionuclide scanning using technetium - labeled hepato iminodiacetic acid ( hida ) is usually ordered after a normal us to exclude acute cholecystitis . riyad et al . , reported that hida scan is very useful in early diagnosis of biliary pain in patients who have a normal abdominal us . however , our patient had no complaints of abdominal pain , and acute cholecystitis was not suspected at first and hida scan was not ordered . a significant fraction of mixed , cholesterol or pigment stones are similar in attenuation to bile and may not be detected on ct . in the present case , our patient had an almost normal ct except for postsurgical changes and a small pericardial effusion . thus , acute cholecystitis can not be ruled out in the absence of ct findings . in a mild form or early manifestation of acute cholecystitis , the ct may be normal and inflammatory changes may be absent on ct in early stages of acute cholecystitis . pet / ct provides both anatomical and functional imaging information and it can scan the whole body in one examination everywhere to assess for possible complications after the surgery . since it relies on detecting the changes in metabolic activity of tissues , it can detect pathology even before anatomic changes are apparent . in acute cholecystitis , there is an increased blood flow from the cystic artery to the gb wall . fdg is taken up by activated inflammatory cells in the gb wall . in the current case , there was an increased fdg uptake in the gb wall , with no uptake in the lumen . this is called the rim sign , and the description is consistent with the previously reported findings of acute cholecystitis on fdg - pet / ct . in contrast , in gb cancers , the fdg uptake is either focal or it fills up the gb , with no photopenic areas . thus , fdg - pet / ct can distinguish between benign and malignant lesions in the gb . finally , the patients can undergo multiple imaging studies for evaluation of acute cholecystitis before cholecystectomy . our case has shown that fdg - pet / ct can eliminate the need for multiple examinations and the delay in treatment . the present case report has shown that both us and ct can miss acute cholecystitis . fdg - pet / ct can diagnose acute cholecystitis in patients with nonspecific clinical symptoms and non - specific imaging results . fdg - pet / ct has a promising role in the management of acute cholecystitis .
we present a case of a 69-year - old patient who underwent ascending aortic aneurysm repair with aortic valve replacement . 
 on postsurgical day 12 , he developed leukocytosis and low - grade fevers . 
 the chest computed tomography ( ct ) showed a periaortic hematoma which represents a postsurgical change from aortic aneurysm repair , and a small pericardial effusion . 
 the abdominal ultrasound showed cholelithiasis without any sign of cholecystitis . 
 finally , a fluorodeoxyglucose ( fdg)-positron emission tomography ( pet)/ct examination was ordered to find the cause of fever of unknown origin , and it showed increased fdg uptake in the gallbladder wall , with no uptake in the lumen . 
 fdg - pet / ct can diagnose acute cholecystitis in patients with nonspecific clinical symptoms and laboratory results .