## **Core Concept**
The patient's presentation is suggestive of a ureteric stone, which is causing severe flank and pelvic pain. The pain typically starts in the flank and radiates down to the groin or labia majora due to the anatomical path of the ureter. The ureter has three main narrow points where stones commonly get obstructed.

## **Why the Correct Answer is Right**
The two specific locations to look for obstructing calculi in the CTs are at the **ureteropelvic junction (UPJ)** and the **ureterovesical junction (UVJ)**.
- The **ureteropelvic junction (UPJ)**, where the renal pelvis transitions into the ureter, is a common site for stone obstruction due to its relatively narrow diameter.
- The **ureterovesical junction (UVJ)**, where the ureter enters the bladder, is another narrow point prone to obstruction.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not specified, but generally, any option not mentioning the UPJ and UVJ would be incorrect because these are the primary sites for obstruction.
- **Option B:** Similarly, without specifics, any option not highlighting these key anatomical locations would not accurately reflect the common sites for stone obstruction.
- **Option C:** This would be incorrect for the same reason as A and B; it doesn't specify the correct locations.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the pain from a kidney stone typically follows the path of the ureter, starting in the flank and radiating to the groin. The three main sites for ureteral obstruction by stones are the UPJ, the point where the ureter crosses over the iliac vessels, and the UVJ.

## **Correct Answer:** D. **Ureteropelvic junction and ureterovesical junction**.

✓ Correct Answer: D. As the ureter crosses the external iliac artery at the pelvic brim and as the ureter passes through the wall of the bladder