====== Air-fluid level ======

When obstruction occurs, both fluid and gas collect. They produce a characteristic pattern called "air-fluid levels". The air rises above the fluid and there is a flat surface at the "air-fluid" interface.

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A [[hypodense]] [[area]] with an [[air fluid level]] within it of approximately 4.4 cm x 3.6 cm is visualized, in the left [[cerebellar hemisphere]], which enhances after IV [[contrast]] and causes a [[mass effect]] on the [[fourth ventricle]] and an increase in the ventricular size of the lateral [[horn]]s, in relation to [[cerebellar abscess]] with secondary [[hydrocephalus]]. Content is visualized inside the left [[mastoid]]. Hypodense foci in subcortical [[white matter]], predominantly bilateral frontoparietal, in [[semioval center]]s, [[corona radiata]], and periventricular, nonspecific, which could be related to small vessel ischemia, being very numerous for the patient's age. Hypodense foci in the left [[external capsule]] suggest Virchow-Robin spaces vs. chronic [[lacunar infarct]]ion. 

Findings in relation to an [[abscess]] in the left cerebellar hemisphere that causes [[hydrocephalus]], especially of the [[lateral ventricle]]s.