Which of the following is NOT a main cause of gallstones?

Hyperlipidemia, which refers to elevated levels of lipids in the blood, does not directly cause gallstones. Gallstones primarily form due to an imbalance in the substances that make up bile. The main causes include conditions that affect the liver's production of bile or the gallbladder's ability to empty properly, which are seen in cirrhosis and gallbladder infections. In addition, hemolytic anemia can lead to increased bilirubin production as red blood cells break down, which can contribute to the formation of stones.

In contrast, while hyperlipidemia may lead to other health issues, it is not specifically linked to the formation of gallstones. Therefore, it stands apart from the other choices that directly involve abdominal or liver conditions associated with bile metabolism or gallbladder function, thereby making it the choice that does not fit as a main cause of gallstones.