What size of effusion is considered "large"?

A "large" effusion is typically defined as one that measures greater than 2 cm. When assessing pleural effusions via ultrasound, effusions larger than this threshold often become clinically significant and may warrant further intervention or management because they can lead to respiratory compromise or indicate more severe underlying pathology.

Effusions greater than 2 cm are usually more readily detectable on imaging, give rise to more pronounced clinical symptoms, and are more likely to require drainage. As the size increases, so does the need for urgent evaluation and treatment, making the classification of effusions crucial in clinical practice.

In contrast, effusions that are less than 2 cm generally do not carry the same urgency for intervention and may be monitored unless they progress or cause symptoms. Thus, defining a large effusion at greater than 2 cm aligns with standard medical practices in assessing the clinical implications of effusions.