Normal cholescintigram in In-111 WBC positive acute acalculous cholecystitis. The converse photopenic 'rim' sign

Nuclear medicine tests for acute gastrointestinal conditions

Acute cholecystitis (AC) and lower-gastrointestinal (GI) bleeding are 2 emergencies commonly encountered in nuclear medicine. Evidence of AC on hepatobiliary scintigraphy (HBS) allows for confident diagnosis and provides support for definitive surgical treatment. Proper patient preparation is essential for HBS including fasting and the use of pharmacologic adjuncts is sometimes required. Pharmacologic adjuncts may also be administered during HBS to shorten the length of the examination and increase its specificity. In the interpretation of HBS, there are several sources of false-positive results to be aware of, most commonly chronic cholecystitis. False-negative results on HBS are usually the result of mistaking another structure, such as a dilated cystic duct, for the gallbladder. Abdominal ultrasound is the appropriate initial test in patients with suspected AC, but HBS is an excellent second tier test for the diagnosis of AC in the work-up of indeterminate cases by sonography. GI bleeding scintigraphy plays an important role in the evaluation and management of patients with acute lower-GI bleeding. Scintigraphy serves to localize sites of active GI bleeding and stratify those patients who would benefit from aggressive treatment (surgery or arteriography) vs those who can be managed medically. Pretest involvement of respective services is critical for successful bleeding site confirmation and therapy by interventional radiology or surgery or both. Single photon emission computed tomography/computed tomography erythrocyte scintigraphy has demonstrated superior accuracy and precision over planar scintigraphy in the diagnosis of acute GI bleeding. Additionally, single photon emission computed tomography/computed tomography scintigraphy of GI bleeding provides useful supplemental anatomical information that benefits patient management.

Hepatobiliary scintigraphy in acute cholecystitis

Hepatobiliary scintigraphy is a mature imaging technique for evaluation of patients with acute cholecystitis (AC). It is effective in calculous and acalculous forms of AC. The test is used in contemporary medical practice as the arbiter when the findings from screening abdominal ultrasound do not fit a clinical picture. It is also performed in severely ill patients who have AC suspected on other testing, but whose frail condition and high operative risk demand the highest level of certainty. This review, therefore, examines all technique variations of hepatobiliary scintigraphy, offering an approach that may best fit a variety of clinical situations and philosophies on AC.