Case 372: Abscess (pyogenic)
85 year-old man with fever. Sonographic search for source of fever.
US: Gas containing, multiloculated, mimicking neoplasm with CEUS
Gray-scale ultrasound demonstrates fluid collection in segment 3, dominated by numerous small gas inclusions (echogenic foci with ring down artifacts). Color Doppler echoes are a result of gas artifacts, there is no increased vascularity. There are several other smaller loculations more superiorly located in segment 2.
Contrast enhanced ultrasound (CEUS) early arterial phase demonstrates a hypervascular capsule surrounding the collection in segment 3 with suggestion of a subtle hypoechoic rim peripherally, suggestive of perifocal edema.
Parenchyma anterior to the collection in segment 3 as well as more superiorly in segment 2 is less vascular than parenchyma more laterally in segment 4, typically due to phlegmon and numerous microabscesses, mimicking washout of a malignancy on later venous phase.
Note that appearance of abscesses and surrounding microabscesses may mimic malignant necrotic masses with infiltrative growth pattern particularly on late venous phase.
Parenchyma in segment 4 is hypervascular on arterial phase due to inflammation in adjacent segments 2 and 3.
Courtesy Dr. Gerd Stuckmann, Institute for Radiology and Nuclear Medicine, Kantonsspital Winterthur, Switzerland.