Pulmonary edema is often caused by left-sided heart failure, where the blood inside the lungs cannot pass to the heart through the pulmonary veins due to dysfunction of the pumping mechanism of the left ventricle, and thus the lung’s blood vessels become congested, leading to the escape of fluids into the air sacs. In patients with co-existing right-sided heart failure, swelling may occur in various sites.
The right side of the heart receives blood returning from all over the body (except for the lungs) through large veins called the superior vena cava and inferior vena cava. This blood has already delivered oxygen and nutrients to the organs of the body and is now returning to the heart to be re-oxygenated. If the right side of the heart is diseased, blood will accumulate inside the right atrium and ventricle, which make up the right side of the heart. Eventually, blood coming from all over the body will not be able to enter the heart, so it remains within the veins of the body, and thereafter this trapped blood may partially pass out of the blood vessels and accumulate between the cells of the body, similar to what happens in the pathogenesis of pulmonary edema. Thus, the patient may experience abnormal swelling of one or more of the following sites: The feet, ankles, legs, lower back, abdomen, hands, or around the eyes.
When a swollen area is pressed on by a finger, the finger leaves a temporary indentation or “pit,” which disappears in a few minutes. These patients may sometimes have a pressure sensation or pain in the upper right abdomen due to a concurrent swelling of the liver. The swelling may be associated with some rather rapid weight gain due to fluid accumulation in the body.