Certified Wound Ostomy Nurse (CWON) Practice Test

What is a bulla?

1. Flat spot of color change greater than 0.5cm in diameter

2. Serous fluid trapped under skin greater than 0.5cm in diameter

3. Loose, stringy, nonviable tissue

4. Scab of dried exudate of body fluid, blood, or pus

The correct answer is: Serous fluid trapped under skin greater than 0.5cm in diameter

A bulla is defined as a fluid-filled lesion that measures greater than 0.5 cm in diameter and is characterized by the presence of serous fluid trapped beneath the skin. This definition pertains to its distinguishable features, which include its size and the nature of the fluid it contains. Bullae can occur in various skin conditions, such as blistering diseases, burns, or certain infections. The key aspect of a bulla is its size and that it harbors serous fluid, which differentiates it from other dermal features. Recognizing this specific definition is crucial in wound and skin assessment, as it allows healthcare professionals to accurately describe and manage skin lesions. This understanding is vital not just for identification but also for determining the appropriate interventions for conditions associated with bullae. Other options, such as flat spots, nonviable tissue, or scabs, do not meet the criteria for a bulla and reflect different types of skin changes.