Hepatología nuclear

RESUMO

For many years the liver and spleen scan has been the study more frequently used by nuclear medicine, however recent advances in the functional evaluztion of the liver through the use of newer isotopes, make the colloid scan less useful. The real progress in nuclear medicine occurs in 1982 with the introduction of the iminodiacetic derivatives (HIDA) tagged with 99mTc. The initial compounds have several important limitations such as the hepatic function and the bilirubin levels, that now with the most recent derivatives such as the mebromofenin (TMB) became less important. This compound has many advantages such as high hepatic concentration (98.1 percent), rapid excretion (ti/2:16 minutes) and great resistance to displacement by bilirubin (70 percent with levels above 20 mgpercent). All these reasons make TMB the ideal agent to study the hepatobiliary physiology. HIDA scan is the most reliable of all the imaging modalities available in the diagnosis of acute cholecystitis with a sensitivity of 92-100 percent, and a specificity of 95-98 percent. The diagnosis of chronic cholecystitis is also simple by this method. Other indications of the HIDA scan is in the study of biliary obstructions, evaluation of biliodigestive anastomosis, biliary fistulas, hepato-biliary ruptures and congenital abnormalities such as choledochal cysts. One of the most important aspect of this technic, is the ability to study hepatic function through the use of the computer and special curves, that allows a direct evaluation of the different steps of hepatic function (uptake, excretion). The function of the transplanted liver can be evaluated this way, and modern Hepatology consider this modality as a very important diagnostic tool.