Percussion is a method of tapping on the body’s surface with fingers, hands, or small instruments to evaluate what lies underneath. It is one of four core physical assessment techniques nurses learn, alongside inspection, palpation, and auscultation. By listening to the sounds produced and feeling the vibrations, a nurse can gather information about organ size, organ borders, tissue consistency, and the presence or absence of fluid in body cavities.
Why Nurses Use Percussion
Think of percussion like tapping on a wall to find a stud. A hollow space sounds different from a solid one, and the same principle applies to the body. Air-filled lung tissue produces a distinctly different sound than a solid organ like the liver, and fluid buildup changes the sound again. These differences give nurses real-time clues without any equipment beyond their own hands.
The four main things percussion helps determine are the size of body organs, the consistency of tissues, the borders where one organ ends and another begins, and whether fluid has collected somewhere it shouldn’t be. A nurse might percuss across the chest to map the lower edge of the lungs, tap across the abdomen to estimate liver size, or check whether a distended abdomen contains air or fluid.
Three Percussion Techniques
Indirect Percussion
This is the most widely used approach and the one nursing students spend the most time practicing. It uses both hands. You place the middle finger of your non-dominant hand flat against the patient’s body, pressing the last finger joint firmly onto the skin. Only that joint should touch the body surface, not the rest of your hand. Then, with the tip of your dominant hand’s middle finger, you tap sharply twice on that pressed-down joint. Your striking finger should come down at a 90-degree angle to the skin, and the motion should be firm, quick, and come entirely from the wrist. Keeping the wrist loose and relaxed is essential for producing a clear sound.
Indirect percussion is the standard technique for assessing the lungs, bowels, bladder, and liver.
Direct Percussion
Direct percussion uses only one hand. You flex the index and middle fingers of your dominant hand and tap their tips directly against the body’s surface at a 90-degree angle. This technique is used in more limited situations, primarily to check for sinus tenderness or to assess an infant’s lungs.
Fist (Blunt) Percussion
Fist percussion uses the pinky side of a loosely clenched fist to deliver a quick, firm blow. It can be done directly against the body or indirectly by placing one hand flat on the patient and striking the back of that hand with the fist. The motion should be brisk, originating at the elbow. This technique isn’t about listening to sounds. It’s designed to detect deep tenderness, most commonly over the kidneys at the costovertebral angle (the area where the lowest rib meets the spine on the back). A positive response, meaning the patient reports sharp pain when tapped, can point toward kidney inflammation or other issues in that region.
The Three Main Percussion Sounds
There are three percussion sounds that are clearly distinguishable from each other: resonance, tympany, and dullness. Learning to tell them apart is the core skill of percussion.
- Resonance is a low-pitched, hollow sound with a moderate duration. This is what you hear over normal, air-filled lung tissue. It’s the baseline sound you compare everything else against when percussing the chest.
- Tympany is a loud, drum-like, higher-pitched sound. You hear it over air-filled spaces like the stomach and intestines. If you percuss over the abdomen, tympany is generally the expected finding.
- Dullness is a soft, thud-like sound with a short duration. It’s what you hear over solid organs like the liver or over muscle, such as the thigh. Dullness in a spot where you’d normally expect resonance is a red flag for something occupying that space.
Two additional sound variations exist at the extremes. Flatness is an even shorter, quieter version of dullness, heard over very dense tissue like bone or large muscle masses. Hyperresonance is louder and lower-pitched than normal resonance, suggesting more air than expected in a space.
What Abnormal Sounds Tell You
The clinical value of percussion comes from comparing what you hear to what you’d expect at a given location. Normal lung fields produce resonance. If you percuss over a lung and hear dullness instead, that area may contain fluid (as in a pleural effusion) or consolidated tissue (as in pneumonia). Comparative percussion, where you tap symmetrical spots on both sides of the chest and compare the sounds, is particularly useful for detecting large pleural effusions.
Hyperresonance over the lung can indicate trapped air, which occurs in conditions like pneumothorax or severe emphysema, where the lung tissue has become over-inflated. In the abdomen, unexpected dullness in areas that should be tympanic could suggest an enlarged organ, a mass, or fluid accumulation.
Measuring Organ Size and Diaphragm Movement
One of the most practical uses of percussion is estimating liver size. By percussing down the right side of the chest at the midclavicular line (an imaginary vertical line through the middle of the collarbone), you listen for the transition from lung resonance to liver dullness. That’s the upper border. Then, percussing up from the abdomen, you find where tympany shifts to dullness, marking the lower border. The distance between these two points is the liver span. The average is about 7 cm in women and 10.5 cm in men. A span that’s 2 to 3 cm larger or smaller than these values is considered abnormal and warrants further evaluation.
Percussion also helps estimate diaphragm movement, called diaphragmatic excursion. You ask the patient to take a deep breath and hold it, then percuss down the back to find where lung resonance changes to dullness, marking the diaphragm’s lowest point. Next, the patient exhales fully, and you repeat the process to find the diaphragm’s highest point. The difference between these two marks is normally 3 to 5 cm, though during forced deep breathing it can be considerably larger. Unequal movement on the two sides can suggest a problem with the nerve that controls the diaphragm or with the lung on that side.
Costovertebral Angle Tenderness
Testing for costovertebral angle (CVA) tenderness is one of the most common uses of fist percussion. The examiner places one hand flat over the area where the lowest rib meets the spine on the patient’s back, then strikes it with a gentle fist blow from the other hand. If this reproduces or worsens the patient’s pain, the test is considered positive. This finding is often associated with kidney infections (pyelonephritis) or kidney stones.
It’s worth knowing, though, that CVA tenderness is not a definitive test for any single condition. Research on patients with suspected kidney stones found the test had a sensitivity of only 65% and a specificity of 50%, meaning it misses a fair number of cases and also produces false positives. It’s best understood as a tool for localizing pain and contributing to clinical reasoning rather than confirming a diagnosis on its own.
Tips for Developing the Skill
Percussion is one of the harder assessment skills to master because it relies on both technique and trained hearing. A few common pitfalls trip up nursing students. The most frequent is a rigid wrist. If the striking motion comes from the elbow or shoulder instead of a relaxed, snapping wrist, the sounds produced are muffled and harder to interpret. The tap should be quick and bouncy, not heavy or lingering.
Another common mistake is pressing the entire non-dominant hand against the body rather than isolating the middle finger’s last joint. Extra fingers touching the skin dampen the vibrations and muddy the sound. Only the joint being struck should have firm contact with the patient. Finally, striking too softly or too hard both cause problems. Too light and you won’t generate enough sound. Too hard and you’ll produce pain without better information. The goal is a moderate, confident tap repeated consistently as you move across a body area.
Practicing on yourself is a good starting point. Percuss over your thigh (dullness), then over your stomach after a meal versus when it’s empty (varying tympany), then over your chest (resonance). The more you build a mental library of what normal sounds like, the faster abnormal findings will stand out.