[Solitary black pigment stones].

Solitary pigment stones of the gallbladder are rare (1.7%). 82.5% are radiopaque, 17.5% radiolucent. 64.8% of radiopaque solitary pigment stones have the structure of a cockade. Such cockades take years to develop. Solitary cholesterol stones with a nucleus of a radiopaque pigment stone should not be treated for litholysis. 8% of solitary cholesterol stones with a cross diameter below 15 mm. possess a radiolucent pigment stone nucleus. X-ray diagnosis for selecting litholytic treatment remains the safest method, especially if the radiologist compares his films regularly with the specimens after surgery.