## Core Concept
Rigler's triad is a radiological finding associated with a specific condition affecting the gallbladder. It consists of three components that are visible on imaging studies, typically X-rays or CT scans. The triad is named after Leo George Rigler.

## Why the Correct Answer is Right
Rigler's triad classically includes:
- **Gallstones** (cholelithiasis): The presence of stones within the gallbladder.
- **Ectopic (or intramural) gallstone**: A stone that has eroded through the gallbladder wall and become embedded in the adjacent liver or other structures.
- **Cholecystocholedochal fistula**: An abnormal connection (fistula) between the gallbladder and the common bile duct.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is not specified, but if it refers to any component of Rigler's triad, then it would be correct and not incorrect.
- **Option B:** Similarly, without specifics, if it aligns with the triad, it's not incorrect.
- **Option C:** If this option does not match any of the components of Rigler's triad, then it is incorrect because it does not belong to the triad.
- **Option D:** This option is stated as the correct answer, implying it does not belong to Rigler's triad.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that Rigler's triad is highly suggestive of a **cholecystocholedochal fistula**, which is a complication of gallstones. This condition can lead to obstructive jaundice and requires prompt medical attention. Recognizing the triad on imaging can significantly aid in diagnosis.

## Correct Answer: D.