Ascites describes an abnormal collection of fluid in the peritoneal cavity.
When ascites collects, the influence of gravity causes it first to accumulate in the flanks of a supine patient. Thus, a relatively early sign of ascites - when at least two litres of fluid have accumulated - is a dull percussion note in the flanks.
With gross ascites, abdominal distension and umbilical inversion may occur and dullness is detectable closer to the middle line. However, an area of central resonance will always persist.
Routine abdominal examination should include percussion starting in the middle line with the finger pointing parallel to the level of the fluid; the percussion note is sounded out towards the flanks on each side.
Ascites should be distinguished from fat, flatus, faeces and foetus.
Last reviewed 01/2018