Hydrostatic bulla (including edema blister, stasis blister) is a common noninfectious blistering condition. Hydrostatic bullae develop due to the rapid accumulation of interstitial fluid in patients with an acute exacerbation of localized or generalized edema (anasarca). Hydrostatic bullae appear and gradually increase in size over time parallel to fluid retention by the patient. This entity is most commonly observed on dependent areas, typically the lower extremities, of older adults who are hospitalized.

Hydrostatic bullae can be seen in various medical conditions associated with an increase in interstitial fluid, including heart failure, renal disease, hepatic cirrhosis, angioedema, hypoalbuminemia, venous occlusion (thrombosis), and lymphedema, or be caused by ingestion of certain drugs (eg, calcium channel blockers).