Procedure
- Lay your non-dominant hand flat on the area to be percussed with fingers spread apart slightly [Figure 17]
- Press the middle finger (or the index or ring finger) firmly against the underlying skin (this finger is referred to as the pleximeter finger)
- Using the tip of the half-bent middle finger (the plexor) of the opposite hand, tap on the distal interphalangeal joint or distal phalynx of the pleximeter finger
- Taps should be short, elastic, and supple, using the wrist; keep the lower arm still and the fingers as relaxed as possible
- Tap two or three times with a frequency of approximately two taps per second; make sure the taps are clearly audible, and use a consistent force for each tap
- Move the fingers calmly. Abrupt movements can startle the patient
Figure 17
- First percuss all abdominal regions systematically (comparative percussion) [Figure 18]
Figure 18: Percussion points
- Percuss the site of abdominal pain last
- For each location, determine the sound of the percussion and whether the percussion is painful
- Lastly, determine by percussion the perimeters of the areas with dull percussion and areas with pain on percussion. For this examination, lay the pleximeter finger parallel to the border in question
These areas can be indicated on a diagram [Figure 19]
Figure 19: Schematic representation of the percussion findings
Focus points
- Determine tympanic regions and areas dull to percussion
Tympany indicates gas retention, and dull percussion suggests a ‘solid’ underlying structure. Normally, the percussion sound changes across the abdomen (‘normal percussion sounds’) - Determine the location and extent of areas with dull percussion sounds (identify the borders of dullness)
Normally, the liver is the only part of the abdomen that is large enough to produce an obvious dull percussion sound. If dull percussion sounds are also found under the right costal arch, the presence of hepatomegaly should be determined (see “The examination of the liver and gall blader”)
If there is dullness above the left costal arch (Traube’s space), it should be determined whether splenomegaly is present (see “The examination of the spleen”) - Be aware of any tenderness on percussion. Determine the location and extent of the area of percussion tenderness
Ask the patient to tell you when the percussion hurts. Be sure to monitor the patient’s face. If the patient feels pain, ask where it hurts. It may be a different location than that percussed. Percussion tenderness is indicative of peritoneal irritation, particularly if it is felt at another location
