Various diseases cause fluids to build up in or around the lungs. The composition of the fluid, such as the minerals, immune cells, bacteria, enzymes and other proteins, can help to establish the diagnosis or cause of fluid buildup. Fluids inside the lung tissues interfere with gas exchange between the lungs and blood, and fluid surrounding the lungs interferes with lung expansion. Both may cause shortness of breath and are important to diagnose and treat.
Transudative Fluid
Transudative fluid is fluid around the lungs with a particular composition. It has relatively low protein, low density and low numbers of cells and tends to be more clear in color. Transudative fluid in the lungs has a number of causes, according to "Harrison's Principles of Internal Medicine," by Anthony S. Fauci, M.D. For example, in kidney disease, proteins can leak out of the blood through the kidneys. These proteins help to keep fluid inside the blood vessels. In their absence, transudative fluid leaks into the lungs. In liver disease, the liver fails to make proteins, leading to the same outcome. If the left side of the heart fails, the right side continues to pump blood into the lungs, and the left side is less effective at removing it from the lungs and pumping it to the body. Pressure builds up in the lungs and fluids leak into the vessels.
Exudative Fluid
Exudative fluid has a higher protein and cell concentration. These are basically thicker fluids than the thinner transudative fluids. Causes of exudative fluid in and around the lungs are from damage to local tissues, such as blood vessels, which allows cells and various debris to build up in the fluid. Infectious pneumonia can cause exudative fluid in the lungs because viruses, bacteria or fungi damage the tissues and cause fluid to leak out. Cancer will also damage the tissues and cause exudative fluid to build up.
Intra-Alveolar Fluid
The windpipe, or trachea, divides to go into the left and right lungs. These main airways are called bronchi. They divide into smaller and smaller airways until reaching millions of tiny sacs called alveoli. The alveoli is where gas exchange occurs. Some diseases damage the alveoi and cause the buildup of fluid inside the alveoli. Acute respiratory distress syndrome is a disease in which fluid builds up in the alveoli. It can be caused by severe infections anywhere in the body, trauma, pancreatitis, inhalation of toxins or shock from any cause.
References
- "Harrison's Principles of Internal Medicine"; 17th Edition; Anthony S. Fauci et al.; 2008
- "Current Medical Diagnosis and Treatment"; 49th Edition; Stephen J. McPhee and Maxine Papadakis; 2009
