Pleural pseudotumor

Last revised by Liz Silverstone on 19 Nov 2023

Pleural pseudotumors refer to encysted focal pleural fluid collections within a lung fissure that may simulate a mass.

Normally there is a similar retractile force applied to the entire pleural space by adjacent lung. When there is a pleural effusion, the elastic recoil of the lung causes each lobe to retract toward the hilum. This can widen the fissures, drawing fluid into them even in non-dependent locations.

The middle lobe (being the smallest lobe), has the greatest tendency to retract, and therefore the horizontal fissure is more prone to developing a pseudotumor.

Pseudotumors almost always occur with transudates: caused by congestive heart failure, cirrhosis, or renal insufficiency.

Lenticular or biconvex opacity along an expected course of a fissure. As with other pleural based pathologies, one of the borders of the pseudomass may be well defined while the other may not. A concurrent dependent pleural effusion aids recognition of a pleural pseudotumor.

May be useful in difficult cases in which the fluid is situated along the edge of the lung, is difficult to relate to a fissure, or has an unusual shape, leading to misinterpretation as a pleural mass.

They usually resolve after therapy with diuretic agents or treatment of the underlying predisposing condition.

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