What is the primary cause of general passive hyperemia in the body?

General passive hyperemia refers to the accumulation of blood in the venous system, leading to increased blood volume in certain areas of the body. The primary cause of this condition is venous obstruction. When there is a blockage in the veins, it inhibits the normal outflow of blood from a certain area. As a result, blood backs up, causing congestion and resulting in passive hyperemia.

This phenomenon can occur due to various factors, such as thrombosis (blood clots) or external compression of veins, which prevent blood from draining effectively. When blood cannot exit an area, it leads to a build-up, resulting in engorged blood vessels and surrounding tissues, contributing to symptoms such as swelling and discoloration.

The other options, while related to vascular conditions, do not primarily cause general passive hyperemia. Increased blood volume generally refers to an active process or systemic condition rather than a localized effect due to venous obstruction. Inflammation typically involves active changes in vascular permeability and blood flow rather than obstruction. Vascular malformations can cause localized issues, but they are not the leading cause of the generalized condition described in this question. Hence, venous obstruction is the most accurate cause of general passive hyperemia.