## Core Concept
Gallstone ileus is a rare complication of gallstones, where a large gallstone enters the bowel through a fistula and obstructs it. The treatment involves relieving the bowel obstruction.

## Why the Correct Answer is Right
The correct treatment for gallstone ileus is usually **surgical intervention**, specifically **enterolithotomy**, which involves making an incision in the intestine to remove the gallstone. This is often the procedure of choice because it is less invasive than other surgical options and has a lower mortality rate.

## Why Each Wrong Option is Incorrect
* **Option A:** Endoscopic retrograde cholangiopancreatography (ERCP) is not typically used for the treatment of gallstone ileus, as the stone is already in the intestine and ERCP is more suited for removing stones from the bile ducts.
* **Option B:** Lithotripsy, or shock wave lithotripsy, is sometimes used to break up kidney stones, but it's not commonly used for gallstones in the intestine due to the risk of bowel injury and the availability of more effective treatments.
* **Option C:** This option is not provided, so we proceed with the understanding that the correct answer is the one chosen.

## Clinical Pearl / High-Yield Fact
A key point to remember is that gallstone ileus typically occurs in elderly patients and has a high mortality rate, partly due to delays in diagnosis. Early surgical intervention is crucial.

## Correct Answer Line
**Correct Answer: D. Surgical intervention (or specifically, enterolithotomy).**