**Core Concept**
Vesicoureteric reflux (VUR) is a condition where urine flows retrogradely from the bladder to the ureter, potentially leading to complications like pyelonephritis and renal scarring. It is a significant concern in children and pregnant women. VUR is often diagnosed using a combination of clinical findings, imaging studies, and cystometric evaluations.

**Why the Correct Answer is Right**
The correct answer is **Micturating Cystourethrogram (MCUG)**, also known as voiding cystourethrogram (VCUG). This imaging technique involves injecting a contrast agent into the bladder through a catheter, followed by a series of X-ray images as the patient urinates. MCUG can demonstrate the retrograde flow of urine into the ureter, thereby confirming the diagnosis of VUR. The mechanism of MCUG relies on the contrast agent outlining the ureters and bladder, allowing for visualization of any abnormal flow patterns.

**Why Each Wrong Option is Incorrect**
**Option A:** Ultrasonography is not the best imaging modality for diagnosing VUR, as it cannot directly demonstrate the retrograde flow of urine. While ultrasound can be useful in assessing renal anatomy and function, it lacks the sensitivity to detect VUR.
**Option B:** Computed Tomography (CT) scans are not typically used to diagnose VUR, as they involve radiation exposure and are not as sensitive as MCUG in detecting ureteral reflux. CT scans may be useful in evaluating complications of VUR, such as renal scarring or pyelonephritis.
**Option C:** Renal scintigraphy, such as using Technetium-99m dimercaptosuccinic acid (DMSA), is useful in assessing renal function and scarring, but it is not the best imaging modality for demonstrating VUR. Scintigraphic studies can help identify complications of VUR, but they do not directly visualize the reflux.

**Clinical Pearl / High-Yield Fact**
Mnemonically, remember that MCUG is the "gold standard" for diagnosing VUR, as it directly visualizes the abnormal flow of urine into the ureters. This is especially important in pediatric patients, where early diagnosis and management of VUR can significantly reduce the risk of renal complications.

**Correct Answer: C. Micturating Cystourethrogram (MCUG)**