The liver scratch test can be used when other exam techniques used to approximate liver size are ineffective or unavailable[2] and is thought to be most useful if the abdomen is distended, too tender for direct palpation, the abdominal muscles are too rigid, or the patient is obese.
[3][4][1] The test is most commonly performed by placing the stethoscope below the xiphoid process and lightly scratching the skin parallel to the expected liver edge.
The examiner begins scratching in the right lower quadrant of the abdomen along the midclavicular line and moves superiorly until the sound abruptly increases in volume.
Multiple variations on the exam also exist including different stethoscope placements such as over the costal margin or liver, percussing the abdomen instead of scratching, or scratching in different patterns i.e. circular or lateral directions.
[1] Despite being commonly taught to medical trainees, the liver scratch test's value as part of the abdominal physical exam has been controversial as it has historically performed poorly.