Venous insufficiency

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Normal Anatomy and Function

• The superficial veins lie in the subcutaneous fatty layer of the body just beneath the skin and superficial to the deep fascia enveloping the body musculature. The principal veins in the legs are the great and lesser saphenous veins and their tributaries; in the arms they are the basilic and cephalic veins and their tributaries.

• The deep veins accompany arteries and bear the same name as the arteries they parallel. It is common in the extremities for there to be two or more veins accompanying a small to medium sized artery.

• The perforating veins penetrate the deep fascia and connect the superficial veins to the deep veins. Those along the inner (medial) side of the lower leg play a major role in the pathogenesis of the postphlebitic leg.

• The intramuscular sinusoidal veins are large, very thin walled, valveless veins within skeletal muscle. They connect directly with the deep veins.

Function

Normal venous flow is dependent on four factors:

• Dynamic Flow: The heart related flow (dynamics/spontaneous flow). Flow in the arterial system is dependent on the pumping action of the heart and the elasticity and muscular activity of the arteries. In contrast, the veins, except for the major superficial veins, are thin walled with paucity of muscle; are designed for distention; and play an insignificant role in directly facilitating flow. Most of the force of the pulsatile flow produced by the pumping heart is lost as blood flows from the arteries through the vast network of capillaries (one cell layer microvessels where selective permeability allows the exchange of O₂ and nutrients with the tissues). What pulsatile flow filters through (dynamic flow) is of low pressure (15 mmHg). Nevertheless, it is sufficient to produce a significant pressure gradient with the right side of the heart where the venous pressure is zero.
• Phasic Flow: Respiration related factors. Phasic flow is the effect of respiration on normal venous flow. In the arms and neck, flow towards the heart increases during inspiration due to the negative intra-thoracic pressure produced. The opposite is true in the legs. With inspiration the diaphragm descends increasing intraabdominal pressure slowing flow. Flow is somewhat increased with expiration with reduced intraabdominal pressure.
• The muscle pump or the venous pump: The muscle pump mechanism is highly developed in the calf muscles. Large venous sinusoids located in these muscles. As they contract, the force helps to emptying the below veins. Contractions of the calf muscles can produce a sufficient pressure to empty the sinusoids into the deep veins. The deep veins are affected with the similar compressing force due to a strong fascial structure. As a result, with each muscle contraction venous blood is pumped towards to the heart.
• The valves: The valves are prevent retrograde flow.

Differential diagnosis of causes of venous insufficiency

• Deep vein thrombosis
• Phlebitis