Percussion: Treatment, Effects & Risks

Percussion is the tapping of the body surface for diagnostic purposes. Percussion is part of the physical examination and allows inferences to be made about the density, size, and consistency of the tissues and organs that lie beneath the tapping area through different sound reflections.

What is percussion?

Percussion is the tapping of the surface of the body for diagnostic purposes. The term percussion comes from Latin. There, “percussio” means to strike or to tap. In percussion, a distinction is made between direct and indirect percussion. In direct percussion, the fingers are used to percuss directly on the skin. This method was first described by Joseph Leopold von Auenbrugger in 1761. Originally, four fingers of one hand were used for this purpose. Today, however, direct percussion also uses the edge of the hand (e.g., for percussion of the renal bearings) or the hand clenched into a fist, for example, for percussion of the spine. In the later developed method of indirect percussion, a finger of one hand is first pressed on the body surface to be examined. Then a finger of the other hand is tapped on this finger, which is also called the plessimeter finger. Instead of the plessimeter finger, a plessimeter can also be used. This is a thin spatula made of plastic or surgical steel. The tapping sound produced with the help of a plessimeter is louder than the tapping sound produced by percussion using the plessimeter finger. In both cases, however, percussion is done loosely from the wrist, with a quick and springy beat. In percussion, different qualities of sound are distinguished. A sonorous sound is one that is loud, sustained, and hollow. A hypersonorous tapping sound is louder, longer lasting, and more hollow than the sonorous tapping sound and may be taken as an indication of excessive air content. A muffled knock sound tends to sound soft and dull. It is also called a thigh sound because the sound is comparable to the sound heard when the thigh is tapped. A tympanic knock sound sounds hollow, full-toned, and tympanic. It indicates cavities or distended bowel loops.

Function, effect, and goals

Percussion can be used in the examination of all organ systems. Percussion of the abdomen is aimed primarily at identifying air accumulation or congestion in the bowel region. If the patient suffers from severe abdominal pain, painless percussion is performed first; otherwise, the abdominal cavity is divided into four quadrants and percussion is performed one quadrant at a time. Normally, the tapping sound in the abdomen is hyposonor over the organs. It may also be hypersonic to tympanic over empty bowel segments. In very large air collections, severe tympany is found. If thigh sound is heard over hollow organs such as the intestine, this may indicate a large tumor or fecal accumulation due to constipation. Percussion can also be used to determine the size of the liver. Percussion of the lungs can be particularly informative. Because the lungs are normally always filled with some air, the percussion sound produced sounds loud and low-frequency. It is a sonorous knocking sound. If the knock sound over the lung is hyposonor, that is, more muffled than the sonorous knock sound, a lung tumor or infectious infiltration of the lung is suspected. In the case of a hypersonor sound, air accumulations or air pockets in the lungs or chest cavity may be the cause. These may be caused, for example, by a pneumothorax, which is an accumulation of air in the gap between the lung and the pleura. A pneumothorax results in difficult breathing and can be life-threatening. If there is cushioning over the lung tissue, the ability to vibrate is reduced. This may be due to extensive tissue compaction or fluid accumulation in the lung or in the gap between the lung and the pleura. Tissue compaction can be caused by tumors. Fibrosis, diseases that result in connective tissue remodeling of the lung tissue, must also be considered in the presence of a hyposonorous palpitation. The same applies to pulmonary edema. Here, the stored water in the alveoli causes the attenuation. Percussion can also be used to test diaphragmatic mobility and thus the flexibility of the lung borders.This would be limited in the case of an overinflated lung, pulmonary fibrosis or neurological deficits. However, it is not only the sound quality that provides information about the patient’s state of health during percussion. If the tapping of the corresponding points causes pain, a pathology of the tapped organs can be assumed. For example, palpitating kidney sites are indicative of renal pelvic inflammation, and palpitating bones may be the result of osteoporosis or tumor disease of the bones.

Risks, side effects and dangers

Percussion is a low-risk examination procedure with no side effects and is therefore an integral part of physical examinations. Basically, there is only one possible complication with percussion and it is also extremely rare. In the case of highly porous bones, for example caused by advanced osteoporosis or a massive bone tumor, the percussed bones can break. However, it should be noted that the vibrations generated by percussion can only penetrate about five to seven centimeters deep. This means that underlying pathological changes cannot be detected by percussion. Thus, a negative finding on percussion does not rule out disease of the corresponding organ. In obese patients, the collection of percutorial findings is additionally complicated. Depending on body circumference, the vibrations may not reach the organs at all, so a thigh sound would be heard almost in a generalized fashion.