**Core Concept**
Haemorrhagic pericarditis refers to the accumulation of blood in the pericardial space, which can be caused by various conditions that compromise the integrity of the pericardium or disrupt the normal coagulation cascade. This condition can lead to cardiac tamponade, a life-threatening complication that requires prompt treatment.

**Why the Correct Answer is Right**
Haemorrhagic pericarditis can occur due to trauma, which causes direct damage to the pericardium, leading to bleeding. Infection, such as tuberculosis or bacterial pericarditis, can also cause haemorrhagic pericarditis by inducing inflammation and coagulopathy. Malignancy, particularly metastatic disease, can cause haemorrhagic pericarditis by eroding the pericardium or inducing a coagulopathy. **Option C:** Radiation therapy is not typically associated with haemorrhagic pericarditis, as it does not directly damage the pericardium or induce coagulopathy.

**Why Each Wrong Option is Incorrect**
* **Option A:** Trauma is a well-known cause of haemorrhagic pericarditis, leading to direct damage to the pericardium and bleeding.
* **Option B:** Infection, such as tuberculosis or bacterial pericarditis, can cause haemorrhagic pericarditis by inducing inflammation and coagulopathy.
* **Option C:** Radiation therapy is not typically associated with haemorrhagic pericarditis, as it does not directly damage the pericardium or induce coagulopathy.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with suspected haemorrhagic pericarditis, it is essential to consider the patient's medical history, including any recent trauma, infections, or malignancies. A thorough physical examination and diagnostic imaging, such as echocardiography or CT scan, can help identify the underlying cause of the condition.

**Correct Answer:** C. Radiation therapy is not typically associated with haemorrhagic pericarditis.