A 40-year old veterinarian presented with complaints of abdominal pain. On examination he was found to be icteric, the liver was palpable, ultrasonography revealed the presence of cyst in the right lobe of liver. The skin hypersensitivity test is performed in this infection in the –

## **Core Concept**
The patient's symptoms, including icterus (jaundice) and a palpable liver with a cyst in the right lobe, suggest a diagnosis of hepatic hydatid cyst, likely caused by *Echinococcus granulosus*. This parasitic infection is common in veterinarians due to their occupational exposure to infected animals. The skin hypersensitivity test mentioned is used for the diagnosis of this condition.

## **Why the Correct Answer is Right**
The correct answer involves the use of a specific skin hypersensitivity test for diagnosing hydatid disease caused by *Echinococcus*. The **Casoni test**, also known as the intradermal test, involves injecting hydatid fluid into the skin. A positive reaction, indicated by wheal and flare, suggests current or past infection. This test, although not commonly used today due to the availability of imaging and serological tests, historically played a role in diagnosing echinococcosis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not correspond to a recognized skin hypersensitivity test used for diagnosing parasitic infections like hydatid disease.
- **Option B:** Similarly, this option does not relate to a standard test for hydatid disease or similar parasitic infections.
- **Option D:** This option is incorrect as it does not accurately represent a skin hypersensitivity test relevant to the diagnosis of echinococcosis.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while the Casoni test was historically used, modern diagnosis of hydatid disease primarily relies on imaging techniques (like ultrasonography, CT, or MRI) and serological tests (e.g., ELISA). The use of skin hypersensitivity tests has declined due to their variability and the risk of anaphylaxis.

## **Correct Answer:** . Casoni test.

✓ Correct Answer: C. Casoni's test