The reason why doctors tap your liver is to assess the size and position of your liver and to also check for and detect any fluid buildup in your abdominal cavity, which can indicate several medical conditions.
The doctor taps your liver through percussion which involves tapping your abdomen and listening to the sounds which are made by the different organs and tissues.
When the doctor taps just below your rib cage it allows the doctor to determine the size and position of your liver.
And a normal live will produce a specific sound when it's tapped and an enlarged liver often produces different sounds.
Percussion can also help to detect any fluid buildup in your abdominal cavity which is called ascites.
Ascites can be caused by several different conditions which include kidney disease, liver disease and heart disease which can be detected through percussion.
Doctors also may gently press on your abdomen which is known as palpation in order to assess the tenderness and feel for any potential masses or abnormalities.
Doctors also tap on your stomach or press on your stomach to find out if the size of your internal organs is normal and to check if anything hurts and to also feel if anything unusual is going on.
Looking and listening at and to your body is all a part of a physical exam.
After birth doctors will press on a woman's stomach which is known as a fundal massage to stimulate uterine contractions and to also help the uterus return to it's normal size and prevent any postpartum hemorrhage.