## **Core Concept**
The question tests knowledge on diagnostic methods for ureteric stones, focusing on sensitivity. Ureteric stones, also known as kidney stones, are a common condition that can cause severe pain and potentially lead to complications like obstruction and infection. Diagnostic tests for ureteric stones include ultrasound, computed tomography (CT) scans, X-rays, and intravenous urograms (IVU).

## **Why the Correct Answer is Right**
The **Non-contrast helical/spiral CT** is considered the most sensitive test for detecting ureteric stones. This imaging technique provides detailed images of the urinary tract and can identify stones as small as 1-2 mm in diameter. It is quick, widely available, and does not require contrast medium, reducing the risk of adverse reactions. The high sensitivity of CT scans for detecting ureteric stones makes them the gold standard for diagnosing this condition.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Ultrasound is less sensitive than CT scans for detecting ureteric stones, especially smaller ones. While it is useful for detecting hydronephrosis (a sign of obstruction) and larger stones, it may miss smaller stones.
- **Option B:** Intravenous Urogram (IVU) or Intravenous Pyelography (IVP) involves injecting a contrast medium to visualize the kidneys, ureters, and bladder on X-rays. Although it can show signs suggestive of ureteric obstruction, it is less sensitive and specific than CT scans for detecting stones themselves.
- **Option C:** X-ray of the kidneys, ureters, and bladder (KUB) can detect some stones, particularly those that are radiopaque (like calcium stones). However, it is less sensitive than CT scans, especially for smaller stones, radiolucent stones (like uric acid stones), and stones that are not aligned with the X-ray beam.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **non-contrast helical/spiral CT scans** have become the diagnostic tool of choice for acute ureteric colic due to their high sensitivity and specificity for detecting ureteric stones, as well as their ability to identify alternative diagnoses.

## **Correct Answer:** . **Non-contrast helical/spiral CT**