Liver span

Liver span is the clinical measurement of the liver's vertical height, assessed at the right midclavicular line. On physical exam it is estimated by percussion: the examiner percusses down the chest until resonance over the lung gives way to dullness (the liver's upper border, usually around the 5th intercostal space) and percusses up from the abdomen until tympany gives way to dullness (the lower border, near the costal margin). The distance between the two points is the liver span.

A normal adult liver span at the midclavicular line is approximately 6–12 cm, with spans tending to run larger in men and in taller individuals. Percussion is an estimate — lung hyperinflation, ascites, or bowel gas can obscure the borders — so imaging such as ultrasound gives a more accurate measurement when precision matters.

The measurement's value is in detecting abnormal liver size. A span greater than about 12–13 cm suggests hepatomegaly, seen with congestion from right heart failure, fatty liver, hepatitis, infiltrative disease, or malignancy. An unusually small span may indicate cirrhotic shrinkage or, acutely, fulminant hepatic necrosis. A palpable liver edge alone does not prove hepatomegaly — a normal-sized liver can be pushed down by hyperinflated lungs — which is why span, not edge position, is the better bedside gauge.

For USMLE Step 1, liver span is a classic reference value tied to hepatic anatomy: know the normal 6–12 cm range at the midclavicular line, the percussion technique, and the causes of an enlarged or shrunken liver. Achievable's USMLE Step 1 course reviews the liver's anatomy and clinical correlates in its gastrointestinal anatomy chapter.