## **Core Concept**
The question tests knowledge on diagnostic methods for ureteric stones, focusing on sensitivity. Ureteric stones, also known as kidney stones, are solid masses that form in the ureters, causing severe pain and potentially leading to obstruction. Diagnostic tests for ureteric stones include imaging techniques such as X-ray, ultrasound, CT scan, and intravenous urography (IVU).

## **Why the Correct Answer is Right**
The correct answer, **CT KUB (Computed Tomography Kidney, Ureter, and Bladder)**, is considered the most sensitive test for detecting ureteric stones. CT KUB provides detailed images of the kidneys, ureters, and bladder, allowing for precise localization and sizing of stones. It is highly sensitive and specific for detecting stones of all compositions except certain drug stones, and it can identify complications such as hydronephrosis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While **Ultrasound** is a useful initial imaging technique for assessing hydronephrosis and sometimes visualizing stones, especially in the renal pelvis or proximal ureter, it is less sensitive than CT KUB for detecting ureteric stones, particularly smaller ones or those in the distal ureter.
- **Option B:** **Intravenous Urography (IVU)**, also known as intravenous pyelography (IVP), involves injecting a contrast medium that is excreted by the kidneys. It can show the outline of the renal pelvis and ureters and detect obstruction but is less sensitive and specific than CT KUB for stone detection. It also carries a risk of contrast-induced nephropathy.
- **Option D:** **X-ray of the abdomen** can detect some kidney stones, particularly those that are radiopaque (like calcium stones), but it is much less sensitive than CT KUB. Many stones, especially uric acid stones, are radiolucent and not visible on plain X-ray.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **CT KUB without contrast** is the gold standard imaging technique for diagnosing ureteric stones due to its high sensitivity and specificity. It's also important to note that while CT KUB is highly effective, it does expose patients to radiation, which should be considered, especially in younger patients or those requiring repeated imaging.

## **Correct Answer:** . CT KUB.