Cystic focal liver lesions in the adult: Differential CT and MR imaging features

Cystic lesions of the liver in the adult can be classified as developmental , neoplastic, inflammatory, or miscellaneous. Although in some cases it is difficult to distinguish these entities with imaging criteria alone, certai n cystic focal liver lesions have classic computed tomographic (CT) and mag netic resonance (MR) imaging features, which are important for the radiolog ist to understand and recognize. Lesions with such features include simple (bile duct) cyst, autosomal dominant polycystic liver disease, biliary hama rtoma, Caroli disease, undifferentiated (embryonal) sarcoma, biliary cystad enoma and cystadenocarcinoma, cystic subtypes of primary liver neoplasms, c ystic metastases, pyogenic and amebic abscesses, intrahepatic hydatid cyst, extrapancreatic pseudocyst, and intrahepatic hematoma and biloma. Specific CT and MR imaging findings that are important to recognize are the size of the lesion; the presence and thickness of a wall; the presence of septa, c alcifications, or internal nodules; the enhancement pattern; the MR cholang iographic appearance; and the signal intensity spectrum. In addition, acces s to critical clinical information remains extremely important. The most im portant clinical parameters defined include age and gender, clinical histor y, and symptoms. An understanding of the classic CT and MR imaging appearan ces of cystic focal liver lesions will allow more definitive diagnosis and shorten the diagnostic workup.