Best investigation for ureteric stones is ?

**Core Concept**
Non-contrast computed tomography (CT) is the best investigation for ureteric stones due to its high sensitivity and specificity in detecting ureteric calculi, allowing for accurate diagnosis and localization.

**Why the Correct Answer is Right**
Non-contrast CT scans use low-dose radiation to produce detailed cross-sectional images of the abdomen and pelvis. This modality is particularly effective in visualizing ureteric stones, especially those that are radiolucent or small. The CT scan can identify the location, size, and shape of the stone, which is crucial for planning treatment. Additionally, CT scans can help identify potential complications, such as hydronephrosis or obstruction.

**Why Each Wrong Option is Incorrect**
**Option A:** Ultrasound is not the best investigation for ureteric stones because it may not visualize the entire ureter, especially in patients with a high body mass index (BMI). Additionally, ultrasound is less sensitive than CT scans in detecting small or radiolucent stones.
**Option B:** Intravenous urography (IVU) involves the use of contrast material and may not be as sensitive as non-contrast CT scans in detecting ureteric stones. IVU also involves radiation exposure and may not provide the same level of detail as CT scans.
**Option C:** Plain radiography (X-ray) is not effective in detecting ureteric stones, especially those that are radiolucent or small. This modality is limited by its inability to penetrate soft tissues and visualize the ureter in detail.

**Clinical Pearl / High-Yield Fact**
When evaluating patients with suspected ureteric stones, it is essential to consider the clinical presentation, including symptoms such as flank pain, hematuria, and urinary frequency. A high index of suspicion and prompt imaging with non-contrast CT scans can help expedite diagnosis and treatment, reducing the risk of complications.

**Correct Answer: C. Plain radiography (X-ray)**