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The Effect of Pleural Fluid on the Diaphragm

1965; Radiological Society of North America; Volume: 84; Issue: 6 Linguagem: Inglês

10.1148/84.6.1080

1527-1315

Richard B. Mulvey,

Lung Cancer Diagnosis and Treatment

While many articles in the literature deal with the distribution and configuration of pleural effusion, there has been little discussion on the effects of this effusion on the dynamics of the diaphragm. As fluid accumulates in a pleural space, the corresponding hemidiaphragm may be depressed by the weight and pressure even though the upper level of the effusion appears unchanged with respect to the rib cage or the mediastinal structures. On the left side the stomach bubble serves as an indicator of the position and contour of the hemidiaphragm. Depression of the right hemidiaphragm by pleural fluid may simulate hepatomegaly as the underlying liver descends. In addition to depression, alterations in the contour and function of the hemidiaphragm may result from pleural fluid. Plain film and fluoroscopic changes representing certain mechanical effects from large pleural effusions will be described in this communication. On frontal views of the chest the apparent upper level of the pleural fluid and the volume of air-bearing lung above it have been observed to correlate poorly with the clinical status of the patient (1). It is also the author's impression that pre- and post-thoracentesis chest films do not appear to correspond with the volume of fluid removed. The chest roentgenogram may appear essentially unchanged after the removal of even a liter or more of fluid, although the patient may be symptomatically improved. It is believed that with left-sided effusions this enigma can be explained in many instances by observation of the position and contour of the hemidiaphragm, as defined by the air-filled fundus of the stomach (Fig. 1). The upper fluid level may appear identical while the underlying hemidiaphragm may be significantly altered in position and function. The author, on the basis of his observations, has classified into three groups the plain film and fluoroscopic changes resulting from left pleural fluid. These are, in order of severity, the domed normal-functioning hemidiaphragm, the flattened fixed hemidiaphragm, and the inverted hemidiaphragm with paradoxical excursions (Fig. 2). Passage of an individual patient from one group to another has been observed as the volume of pleural fluid increased or decreased. In general, other factors being equal, the severity of dyspnea seems to correlate better with the contour of the hemidiaphragm below the fluid than with the upper level of the pleural fluid and the volume of aerated lung above it. The Domed Functioning Hemidiaphragm Even with large pleural effusions the hemidiaphragm, as defined by the air-filled stomach, is often not depressed and usually maintains its dome-like configuration (Fig. 2, A). Fluoroscopically, the aerated floating lung, which has been displaced into the upper chest by the fluid, can be observed to ventilate normally with respiration. The upper level of the fluid and the stomach bubble are also seen to undergo normal respiratory excursions.