The exact cause of liver cysts is not known. They may be congenital (present at birth) or developed at a later stage. While majority of the patients have only one cyst having a thin outer wall, multiple cysts are diagnosed in some patients. In most cases, the cysts are filled with a clear fluid, or at times, they are nothing more than empty sacs. They are benign, and do not disturb liver function. Very rarely, cysts on the liver pose health risks, like malignancy and infections.