Snow storm appearance on USG is seen in :
**Core Concept**
The snow storm appearance on ultrasound (USG) refers to the echogenic pattern seen in certain liver conditions, characterized by a mixture of hyperechoic and hypoechoic areas, resembling a snowstorm. This phenomenon is due to the presence of regenerating liver tissue, which contains a mixture of normal and abnormal hepatocytes.
**Why the Correct Answer is Right**
The snowstorm appearance is typically seen in liver conditions such as cirrhosis, where there is a mixture of regenerating nodules and fibrotic tissue. The regenerating nodules contain a mixture of normal and abnormal hepatocytes, which give rise to the characteristic echogenic pattern. This pattern is due to the presence of a combination of hepatocytes with normal and abnormal cellular structure, which creates a mixture of bright and dark areas on the ultrasound image. The fibrotic tissue also contributes to the echogenic pattern by creating a background of bright echoes.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the "spider web" appearance is typically seen in portal hypertension, where there is a network of collateral vessels forming a web-like pattern.
* **Option B:** This option is incorrect because the "halo sign" is typically seen in focal nodular hyperplasia (FNH), where there is a characteristic echogenic nodule with a surrounding halo of hypoechogenicity.
* **Option C:** This option is incorrect because the "target sign" is typically seen in focal nodular hyperplasia (FNH), where there is a central echogenic nodule surrounded by a hypoechoic halo.
**Clinical Pearl / High-Yield Fact**
The snowstorm appearance on ultrasound is a characteristic feature of cirrhosis and can be used as a diagnostic clue in patients with liver disease. It is essential to recognize this pattern to differentiate it from other liver conditions that may present with similar ultrasound findings.
**Correct Answer:** C.