Heart failure and Right Sided pleural effusion
- Azygous Vein theory
Dilatation of right heart exerts pressure on the hilum of right lung with subsequent compression of the azygous vein which runs in same anatomical space. The azygous vein drains a portion of parietal pleura of right lung. Azygous vein compression is thought to increase hydrostatic pressure along capillaries of parietal pleura and produce pleural effusion.
- Dilatation of right and left aria impinge on pulmonary veins and raise pressure across capillaries of visceral pleura , producing pleural effusions. Because of anatomical position and structure of right atrium, compression of right pulmonary veins may be more common than compression of left pulmonary veins explaining right sided preponderance of right pleural effusion.
- Right pulmonary venous pressures are higher than left pulmonary venous pressures because of combination of anatomical relationship between left ventricle and lungs , as well as patient positioning in bed. As patients with congestive cardiac failure often prefer right lateral recumbent position , right pulmonary venous pressures were thought to be higher than left pulmonary venous pressures producing predominantly right sided pleural effusions
