Pulmonology coders will be able to report thoracentesis more readily when they have a clear understanding of the differences between the diagnostic and therapeutic nature of the procedure. Pulmonologists may perform thoracentesis for either diagnostic or therapeutic purposes and may include related procedures in addition to E/M services. The two pleurae cover the lungs and chest wall. Usually they touch, helping to reduce friction during breathing. Fluid can get trapped between the visceral pleura (next to the lungs) and parietal pleura (next to the chest wall). When this happens, pulmonary physicians often perform a thoracentesis to help remove the fluid or to diagnosis its source. During a thoracentesis, the pulmonologist inserts a small needle between the patient's ribs into the space between the two pleurae. He or she drains the fluid and usually sends it to a laboratory for cultures and other diagnostic tests. Occasionally, disease, such as cancer, causes fluid to build up, and the patient experiences shortness of breath or coughing. When this happens, the physician performs a therapeutic thoracentesis to get the fluid out, letting the lungs expand and helping the patient get relief.