How is pleurisy diagnosed?

The pain of pleurisy is very distinctive. The pain is in the chest and is usually sharp and aggravated by breathing. However, the pain can be confused with the pain of:

• Inflammation around the heart (pericarditis)

• Heart attack (myocardial infarction)

• Air leak inside the chest (pneumothorax)

To make the diagnosis of pleurisy, the physician examines the chest in the area of pain and can often hear (with a stethoscope) the friction that is generated by the rubbing of the two inflamed layers of pleura with each breath. The noise generated by this sound is termed a pleural friction rub. (In contrast, the friction of the rubbing that is heard with pericarditis is synchronous with the heartbeat and does not vary with respiration.) With large amounts of pleural fluid accumulation, there can be decreased breath sounds (less audible respiratory sounds heard through a stethoscope) and the chest is dull sounding when the doctor taps on it (dullness upon percussion).

A chest x-ray in the upright position and while lying on the side is an accurate tool in diagnosing small amounts of fluid in the pleural space. It is possible to estimate the amount of fluid collection by findings on the x-ray. (Occasionally, as much as 4-5 liters of fluid can accumulate inside the pleural space.)

Ultrasound is also a very sensitive method of detecting the presence of pleural fluid.

A CT scan can be very helpful in detecting trapped pockets of pleural fluid as well as in determining the nature of the tissues surrounding the area.

Removal of pleural fluid with a needle and syringe (aspiration) is essential in diagnosing the cause of pleurisy. The fluid's color, consistency, and clarity are analyzed in the laboratory. The fluid analysis is defined as either an "exudate" (high in protein, low in sugar, high in LDH enzyme, and high white cell count; characteristic of an inflammatory process) or a "transudate" (containing normal levels of these body chemicals). Causes of exudative fluid include infections (such as pneumonia), cancer, tuberculosis, and collagen diseases (such as rheumatoid arthritis and lupus). Causes of transudative fluid are congestive heart failure and liver and kidney diseases. Pulmonary emboli can cause either transudates or exudates in the pleural space.

The fluid can also be tested for the presence of infectious organisms and cancer cells. In some cases, a small piece of pleura may be removed for microscopic study (biopsied) if there is suspicion of tuberculosis (TB) or cancer.