Crescent sign

Medical sign indicating subcapsular hematoma or pneumothorax

Crescent sign in medicine

The crescent sign is a radiological finding that can indicate various medical conditions, most notably in the context of orthopedics and pulmonology. It is characterized by a crescent-shaped radiolucency or radiopacity seen on imaging studies such as X-ray or CT scan.

Orthopedic context

In orthopedics, the crescent sign is often associated with avascular necrosis (AVN) of the femoral head. This sign appears as a subchondral radiolucent line on the superior aspect of the femoral head, indicating the presence of a subchondral fracture. The appearance of the crescent sign in this context suggests the collapse of the necrotic bone and is a critical indicator of disease progression in AVN.

Pulmonary context

In pulmonology, the crescent sign can be seen in cases of pneumothorax or subpulmonic effusion. In a pneumothorax, the crescent sign may appear as a crescent-shaped area of increased radiolucency at the lung apex, indicating the presence of air in the pleural space. This sign is crucial for diagnosing a pneumothorax, especially in supine patients where the air may collect anteriorly.

Abdominal context

The crescent sign can also be observed in the abdomen, particularly in the context of subcapsular hematoma of the spleen or liver. In these cases, the crescent sign appears as a crescent-shaped area of increased density on imaging studies, indicating the presence of blood between the capsule and the organ parenchyma.

Imaging and diagnosis

The identification of the crescent sign requires careful analysis of imaging studies. Radiologists and clinicians must consider the clinical context and correlate imaging findings with patient symptoms and history. The presence of a crescent sign can guide further diagnostic testing and influence treatment decisions.

Crescent sign in avascular necrosis of the femoral head

Related pages

• Avascular necrosis
• Pneumothorax
• Subcapsular hematoma
• Radiology