Percussion and physical diagnosis: separating myth from science

There are three percussion sounds, which are easily distinguishable by objective measures: tympany (heard with percussion over the intestines), resonance (heard over the normal lung), and dullness (heard over the liver or thigh). The percussion sound that is produced reflects the ease with which the body wall vibrates, which in turn is influenced by many variables, including the strength of the stroke, the condition and state of the body wall, and the underlying organs. Underlying organs or disease may cause dullness to occur at distant sites. There is good interobserver agreement among clinicians with regard to calling a particular percussion sound dull, resonant, or hyperresonant. In contrast, there is very poor interobserver agreement among clinicians using percussion to measure the span of a particular organ. The use of comparative percussion can detect most large pleural effusions, but this method is able to detect only a few pneumonias. Shifting dullness is a reliable and fairly accurate sign for the detection of ascites. Both of these techniques can still be recommended after a review of the literature. Topographic percussion (e.g., using percussion to locate the heart, liver, and spleen borders or dimensions) has poor reproducibility, is significantly inaccurate in many patients, and has little clinical utility; it should be abandoned. Its fundamental principle--that sound waves penetrate only several centimeters of tissue, resulting in a note reflecting abnormalities only in this layer of tissue--is incorrect. Auscultatory percussion offers no advantage over conventional percussion, with the possible exception of auscultatory percussion of the shoulder. Auscultatory percussion should be abandoned as a bedside diagnostic technique.