In what condition does passive hyperemia typically occur?

Passive hyperemia, also known as venous congestion, occurs when there is a decreased venous drainage from a particular area. This condition leads to an accumulation of blood in the affected region, as the blood that enters the tissue cannot effectively exit due to obstruction or narrowing of the veins. This congested state causes an increase in the volume of blood within the vessels, ultimately resulting in the characteristic symptoms associated with passive hyperemia, such as swelling and cyanosis.

In contrast, increased blood flow refers to active hyperemia, where there is an increase in arterial blood supply, often due to physiological needs or inflammation. Excessive oxygen is not directly related to hyperemia, as hyperemia itself pertains to blood volume rather than oxygen levels. Capillary rupture is a separate pathological issue that leads to bleeding and does not describe the mechanism of passive hyperemia, which specifically revolves around issues with venous drainage. Thus, the correct choice of decreased venous drainage provides a clear understanding of the underlying cause of passive hyperemia.