How to perform percussion of the abdomen
Percussion is an important portion of the abdominal exam. It consists of tapping on the body wall and eliciting a sound that has different pitches for different structures. The changes in pitch differ depending upon the organ being percussed.
Tapping during percussion can also cause the movement of fluid. This motion caused by percussion can help to assess the presence of fluid in the abdomen.
How to percuss the abdomen
Good technique is important for this portion of the exam. While the patient is supine and comfortable, use your non-dominant hand as the base and lay down the palmar aspect of the hand on the abdomen. With your dominant hand, use firm constant pressure applied from the middle finger (you can also use two fingers) to tap down on the dorsum of the middle finger of the base hand.
Two taps are applied in each region. You may want to start in the right upper quadrant and move clockwise, ending with the epigastric and suprapubic regions.
Tympany versus dullness
As mentioned previously, percussion elicits sounds that have different pitches across various structures—making distinct sounds. In the abdomen, the predominant sounds are either tympany or dullness.
Tympany is typically heard over air-filled structures such as the small intestine and the large intestine. Dullness is typically heard over fluid or solid organs such as the liver or spleen, which can be used to determine the margins of the liver and spleen. This can help with estimating the size of these organs and can help to identify organomegaly (i.e., enlarged organs).
What abdominal organs should you percuss?
Start over the right midclavicular line to percuss the liver. The midclavicular line is an imaginary line that exists bilaterally on the patient’s abdomen. It starts in the center of the clavicle and runs medially through the nipple.
To find the upper border of the liver, percuss along the right midclavicular line starting from around the third intercostal space down towards the right costal margin (i.e., the lower edge of the rib cage). The normal upper border of the liver should be around the fifth intercostal space. To locate the lower border of the liver, percuss along the right midclavicular line from below the umbilicus upwards to the right costal margin. The normal lower border of the liver should be at the right costal margin.
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Percuss on the left midclavicular line at the level of the fifth intercostal space (i.e., between the rib) and work in a diagonal line towards the posterior axillary line (e.g., at the left costal margin) to locate the spleen.
Keep in mind that there are different ways to percuss certain organs, and these may vary geographically. For example, in some European countries percussion of the spleen is performed on a patient in a lateral decubitus position.
How to perform ascites percussion
Free fluid in the abdominal cavity is referred to as ascites. Normally, a small amount of fluid is present in the abdomen. But, a large amount is usually pathological. To perform a full exam for fluid, combine both percussion and palpation.
Dullness over flanks
While the patient is lying supine, fluid shifts to the flanks and the air-filled bowel moves anterior-superior. For ascites percussion, percuss from the posterior axillary line in each flank, starting from the one furthest from you and head towards the midline.
In a person with ascites, the flanks will sound dull and the midline should sound tympanic, creating an air-fluid level. Test for shifting dullness, which is a way to confirm that the dullness is caused by ascites. Have the patient roll towards you in the lateral decubitus position. If ascites is present, the air-filled bowel loops will shift and remain at the surface of the fluid and the air-fluid level will shift as well.
Another test for ascites involves trying to illicit a fluid thrill. A fluid thrill is felt as a ripple of fluid against one’s hand. It can be seen in patients with very obvious ascites.
Elicit a fluid thrill by placing your left hand along the posterior left flank, and your right hand at the posterior right flank and gently tap with the tips of your right-hand fingers in a right to left motion. Note if there is a wave of fluid that hits your left hand. You can also use your fingers on the right hand to flick the abdomen at the right costal margin to see if there is a ripple of fluid that moves toward your left side.
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