Are there any distinctive CT and MR imaging features of specific types of nonparenchymal cystic lesions?
Some imaging features listed below are useful to suggest specific types of nonparenchymal cystic lesions. Otherwise, there is much overlap in the CT and MR imaging appearance of nonparenchymal cystic lesions.
Lymphangiomas, benign cystic mesotheliomas, and tailgut cysts are typically multilocular, whereas simple lymphatic, simple mesothelial, enteric duplication, enteric, bronchogenic, epidermoid, and dermoid cysts are typically unilocular. Enteric duplication cysts have diffusely thickened walls because they contain all of the normal bowel wall layers, whereas enteric cysts have thin walls because they are lined only by enteric mucosa.
Enteric duplication cysts and enteric cysts are typically located adjacent to bowel loops, extrathoracic bronchogenic cysts and extralobar pulmonary sequestration are typically located in the subdiaphragmatic retroperitoneum, and tailgut cysts are typically retrorectal in location.
Mature cystic teratoma may contain fat attenuation or fat signal intensity components, whereas cystic or necrotic lymphadenopathy and cystic or necrotic neoplasms typically have residual soft tissue enhancing components.
Hemorrhagic fluid collections typically have nonenhancing high attenuation and high T1-weighted signal intensity fluid, sometimes with a hematocrit effect due to layering of cellular components of blood. Uriniferous fluid collections will characteristically be associated with leakage of excreted intravenous contrast material from the urothelium during the delayed phase of enhancement. Enteric and infectious fluid collections sometimes contain foci of very low attenuation and very low signal intensity gas.