Problems and pitfalls in the echocardiographic assessment of pericardial effusion.

The echocardiographic diagnosis of pericardial effusions is usually based on visualization of a sonolucent circumcardiac space of varying width. However, potential fallacies in interpretation can arise if sonolucent spaces adjacent to the heart (pleural effusions, ascites, pericardial cysts) are mistaken for pericardial effusions. Loculated pericardial effusions, especially if unusual in location or configuration, can cause diagnostic difficulty on occasion. The differential diagnosis of various "solid" echoes within a pericardial effusion is of clinical relevance, yet not widely discussed. Inflammatory tissue, neoplastic involvement, pus, caseous material, and extravasated blood all have characteristic echocardiographic morphologies. All of the various reported echocardiographic signs of tamponade do not have the same significance, so that caution is necessary not to over- or under-read tamponade. Chamber collapse can be absent in real tamponade in specific situations. On the other hand, "regional" tamponade can occur if loculated pericardial effusions are sufficiently large and high tension; echocardiographic appearances are "atypical" but diagnostically valuable if correctly interpreted. These and certain other unusual variants of tamponade deserve to be better known among echocardiographers not only because of their intrinsic interest, but also to avoid potential pitfalls in the echocardiographic assessment of patients with suspected disease.