The unifying abnormality in all chronic venous diseases is:

The concept of ambulatory venous hypertension is critical in understanding chronic venous disease. In this condition, there is a pathological increase in venous pressure that occurs when a person stands or walks. This elevated pressure is often the result of valve incompetence in the venous system, leading to inadequate blood flow back to the heart. Over time, this sustained high pressure can cause a range of symptoms and complications, including edema, skin changes, and venous ulcers.

Chronic venous disease manifests in different forms, such as varicose veins, chronic venous insufficiency, and post-thrombotic syndrome. Despite these variations, the underlying mechanism that drives these conditions is commonly linked to ambulatory venous hypertension. Essentially, it's this unifying abnormality that leads to the symptomatic presentation seen in patients dealing with chronic venous diseases.