Venous reflux is backward blood flow in the veins, most commonly in the legs. Normally, one-way valves inside your veins keep blood moving upward toward the heart. When those valves weaken or stop closing properly, blood falls back down and pools in the lower legs. This pooling is the root cause of varicose veins, leg swelling, skin changes, and in advanced cases, open wounds that are slow to heal.
How Vein Valves Fail
Your veins contain small two-flap (bicuspid) valves spaced along their length. Every time your calf muscles contract, they squeeze blood upward, and the valves snap shut behind it to prevent backflow. Reflux happens when those valves can no longer close tightly. There are two main reasons this occurs.
The first is structural: the valve flaps themselves become weakened or misshapen, or the vein wall stretches so wide that the flaps can no longer meet in the middle. This is the most common cause of reflux in the superficial veins, the ones closer to the skin’s surface. The second is damage from a prior blood clot (deep vein thrombosis). A clot triggers inflammation that scars the valve, creates adhesions, and narrows the channel. This type of damage is more common in the deep venous system.
There’s also a domino effect between the two systems. Veins called perforators connect your deep veins to your superficial ones. When perforator valves fail, the higher pressure from the deep system pushes into the superficial veins, stretching them further and preventing their valves from closing. One area of valve failure can cascade outward.
Who Is Most at Risk
Several factors increase the likelihood of developing venous reflux. Age, pregnancy, and a family history of vein problems are among the strongest predictors. Occupations that require prolonged standing, such as teaching, law enforcement, or working a bus route, put sustained pressure on leg veins. Obesity compounds the problem by increasing abdominal pressure, which makes it harder for blood to travel upward from the legs.
For women, hormonal supplementation raises the risk of blood clots and subsequent valve damage. For men, smoking is a notable contributor. Any prior leg injury or vein procedure can also set the stage for reflux down the line.
What Venous Reflux Feels Like
The symptoms tend to build gradually and worsen over months or years. Early on, you might notice your legs feeling heavy or tired by the end of the day, especially after standing. Swelling around the ankles is common, often worse in the evening and better after a night’s sleep. Other typical symptoms include:
- Tight, achy calves or itchy legs
- Pain while walking that improves with rest
- Painful leg cramps or charley horses, particularly at night
- An uncomfortable urge to move your legs (restless legs)
- Visible varicose veins
- Brownish discoloration near the ankles
These symptoms overlap with arterial problems like peripheral artery disease, but the two conditions behave differently. Arterial disease causes cramping during activity because the muscles aren’t getting enough oxygen-rich blood, and it often makes the foot feel cold. Venous reflux causes heaviness and swelling from blood pooling, and the skin tends to thicken and darken rather than become pale or shiny. The distinction matters because the treatments are completely different.
How It Progresses Over Time
Venous reflux follows a recognized progression. In the earliest stage, there are no visible signs at all. Small spider veins or slightly enlarged veins may appear first. True varicose veins, defined as 3 millimeters or wider, come next. As pooling continues, persistent swelling develops that no longer resolves overnight.
Left untreated, the chronic high pressure in the veins forces red blood cells through the vessel walls into surrounding tissue. Those cells break down and deposit iron pigments, turning the skin brown. Ongoing inflammation leads to a condition where the skin and fat layer beneath it become hardened, stiff, and contracted. The skin looks shiny and feels woody to the touch.
The final stage is a venous ulcer, an open sore typically near the ankle. These ulcers form because the tissue has been starved of proper nutrition and oxygen for so long that it slowly dies. Even a minor bump or scrape can trigger rapid ulceration in skin that has already been compromised. Venous ulcers are notoriously difficult to heal and can leak fluid, develop an odor, and become infected.
How Venous Reflux Is Diagnosed
The standard test is a duplex ultrasound, which combines a regular ultrasound image with a measurement of blood flow direction and speed. During the exam, a technician will compress your calf or have you perform specific maneuvers to provoke any backflow. Reflux is considered significant when backward flow lasts longer than 0.5 seconds in the superficial veins or longer than 1.0 second in the deep veins. These time thresholds help distinguish minor, clinically irrelevant leakage from reflux that is likely causing symptoms.
Conservative Treatment With Compression
Compression stockings are the first line of management and remain part of the treatment plan at every stage. They work by applying graduated pressure, tightest at the ankle and looser toward the knee, to help push blood upward and counteract the pooling effect.
Stockings come in different pressure levels. Low compression (under 20 mmHg) can relieve discomfort and improve quality of life in early-stage disease with spider veins, mild varicose veins, or light swelling. Medium compression (20 to 30 mmHg) provides additional benefit for swelling and symptoms, though studies suggest it may not be dramatically more effective than the 15 to 20 mmHg range for many people. High compression (30 to 40 mmHg) is reserved for more advanced disease and is the most effective level for healing venous ulcers and preventing them from coming back. The general principle is to wear the highest compression level you can tolerate comfortably.
Beyond stockings, regular walking, leg elevation, weight management, and avoiding long periods of standing or sitting all help reduce the pressure load on your veins.
Procedures to Close Damaged Veins
When conservative measures aren’t enough, several minimally invasive procedures can shut down the faulty vein entirely. Blood then reroutes through nearby healthy veins. These are typically outpatient procedures done with local anesthesia.
Radiofrequency ablation uses a thin catheter inserted through a small incision below the knee. Electrodes at the tip deliver bursts of heat energy, heating the vein wall in 20-second intervals until it shrinks and collapses. Endovenous laser treatment works similarly, using a laser fiber inside the catheter to heat and seal the vein. Both approaches leave no external wound beyond the insertion point.
Sclerotherapy takes a different approach. A liquid or foam solution is injected directly into the affected vein, irritating its lining and causing it to swell shut. For larger veins, ultrasound-guided foam sclerotherapy delivers a chemical foam through a catheter, with real-time imaging ensuring the foam reaches the right segments. The vein collapses and is gradually absorbed by the body over the following weeks.
The choice between these procedures depends on the size and location of the affected veins, but all of them aim to eliminate the source of backward flow and redirect blood through veins with functioning valves.