Vesicoureteric reflux is demonstrated by using
**Core Concept**
Vesicoureteric reflux (VUR) is a condition where urine flows retrogradely from the bladder into the ureter or kidneys, potentially leading to renal damage or infection. Diagnosing VUR involves imaging studies that can demonstrate the reflux of contrast material from the bladder into the ureters.
**Why the Correct Answer is Right**
MAG3 (Mercaptoacetyltriglycine) scan using Tc-99m is a dynamic renal scintigraphy technique that provides real-time imaging of the kidneys and ureters. It is particularly useful for assessing renal function and detecting vesicoureteric reflux. The MAG3 scan uses a small amount of the radioactive tracer Tc-99m, which is excreted by the kidneys and can be visualized using a gamma camera. When VUR is present, the contrast material will appear in the ureters and kidneys in a delayed manner, indicating retrograde flow from the bladder.
**Why Each Wrong Option is Incorrect**
**Option A:** DMSA (Dimercaptosuccinic acid) scan is primarily used to assess renal cortical scarring and function, particularly in patients with a history of urinary tract infections or suspected pyelonephritis. While it can provide information on renal anatomy, it is not the best modality for demonstrating VUR.
**Option B:** DTPA (Diethylenetriamine pentaacetate) scan is another dynamic renal scintigraphy technique that evaluates renal function and blood flow. However, it is not as sensitive as MAG3 for detecting VUR due to its slower excretion and lower spatial resolution.
**Option D:** I123 iodocholesterol is a radioactive tracer used in adrenal gland imaging, particularly for diagnosing primary aldosteronism or Cushing's syndrome. It is not relevant to the diagnosis of VUR.
**Clinical Pearl / High-Yield Fact**
When interpreting renal scintigraphy studies, it's essential to understand the characteristics of each tracer and the specific indications for each modality. MAG3 scan is particularly useful for assessing renal function and detecting VUR, especially in pediatric patients.
**✓ Correct Answer: C. MAG3 - Tc 99**