**Core Concept:** Fulminant ulcerative colitis (UC) is a severe and life-threatening form of ulcerative colitis (UC), characterized by extensive involvement of the large intestine (colon) and rectum, leading to severe inflammation, bleeding, and systemic complications. First-line therapy for fulminant UC aims to induce remission and prevent complications.

**Why the Correct Answer is Right:** The correct answer, **A. Methotrexate**, is used as the first-line therapy for fulminant ulcerative colitis. Methotrexate is an immunosuppressive drug that works by inhibiting cell division and reducing inflammation. In the context of fulminant UC, methotrexate helps to suppress the immune response and reduce inflammation, ultimately leading to mucosal healing and preventing complications.

**Why Each Wrong Option is Incorrect:**

**B. Steroids (e.g., Prednisolone)**: While steroids are effective in inducing remission in mild to moderate UC, they are not the first-line therapy for fulminant UC. Steroids have a higher risk of complications, such as osteoporosis, glucose intolerance, and impaired wound healing, which can exacerbate the severity of fulminant UC.

**C. Immunosuppressants (e.g., Azathioprine)**: Immunosuppressants like azathioprine are often used in combination with steroids for the treatment of UC. However, they are not the primary choice for fulminant UC due to their slower onset of action and increased risk of infections compared to methotrexate.

**D. Surgery (colectomy)**: Surgery is often required in severe cases of fulminant UC but is not considered a first-line therapy. Surgery is usually reserved for patients who do not respond to medical treatment or experience complications from the disease.

**Clinical Pearl:** In cases of fulminant ulcerative colitis, a multi-disciplinary approach is crucial, involving gastroenterologists, surgeons, and intensivists. Treatment should be tailored according to the severity and complications of the patient's condition.

**Correct Answer Explanation:** When treating fulminant UC, methotrexate is the appropriate first-line therapy due to its faster onset of action, lower risk of complications compared to steroids, and potential synergistic effect with other medications like azathioprine.

**Why Each Wrong Option is Incorrect:**

**Option B: Steroids (e.g., Prednisolone)**: Although steroids can induce remission in mild to moderate UC, their use in fulminant UC may lead to increased complications, such as osteoporosis, glucose intolerance, and impaired wound healing. Additionally, the slower onset of action makes them unsuitable for urgent treatment required in fulminant UC.

**Option C: Immunosuppressants (e.g., Azathioprine)**: Immunosuppressants, like azathioprine, are often used in combination with steroids or methotrexate for UC treatment. However, they are not considered the primary