About Phlebitis
Superficial thrombophlebitis simply means blood clotting and inflammation in the superficial veins.
This is a common inflammatory disorder of veins in the legs.
This condition is NOT the same as
deep vein thrombosis, where clotting takes place within the DEEP veins and not the superficial veins, and often there is no inflammation.
DVT is always a serious medical condition and requires medical intervention. Superficial thrombophlebitis is much less serious, but often causes a great deal of distress due to the pain and fact that the patient has a "blood clot in the leg"
Superficial Thrombophlebitis
What is superficial thrombophlebitis?
Superficial thrombophlebitis can happen in any of the superficial veins in the body. We are more concerned about the veins in the legs. Any healthy or diseased vein can be affected under the right circumstances. Varicose veins are obviously more prone to this condition. Superficial vein thrombosis often settles on its own, but it is not always benign. At presentation around a quarter of patients are found to have a concurrent deep vein thrombosis or pulmonary embolism, frequently without symptoms1. The risk depends on where the clot is, how extensive it is, and the patient's own risk factors, so any new hard, red, tender vein should be assessed rather than assumed to be harmless.
Symptoms
Superficial thrombophlebitis is diagnosed by a doctor on clinical grounds. Examination of the area would reveal tender superficial veins, redness, warm and slight swelling. Further investigation with duplex ultrasound might be undertaken to ascertain the extent of the thrombosis or clotting.
Causes
Superficial thrombophlebitis can occur spontaneously, especially in the greater saphenous vein in the legs. Although the etiology is frequently obscure, superficial venous thrombosis is most often associated with one of the following : vein injury(which can result from trauma, infection, or inflammation), stagnant or turbulent bloodflow(often found in varicose veins), or changes in blood constituents (dehydration for instance lowers the water content of blood, making it more prone to clotting).
Complications
Complications are an uncommon feature of superficial thrombophlebitis. However the following can happen - extension of the clot into the deep vein, with resultant deep vein thrombosis and possible pulmonary embolism. Conversion into an infected form of phlebitis known as septic thrombophlebitis. After the acute episode hyperpigmentation of the skin can persist. Also a persistent firm nodule under the skin.
Assessment: why a duplex scan matters
Superficial vein thrombosis used to be treated on clinical appearance alone. It is now recognised that appearance is a poor guide to risk, and that management depends on findings that can only be established with a duplex ultrasound scan34.
The scan establishes four things:
- The length of the clot. Thromboses of 5 cm or more behave differently from short, localised segments.
- How close it lies to the deep veins. Proximity to the saphenofemoral junction in the groin, or the saphenopopliteal junction behind the knee, is the single most important factor. A threshold of 3 cm from the junction is used to separate higher from intermediate risk.
- Whether a deep vein thrombosis is already present. This is common and frequently silent, which is why the deep veins are scanned as well as the affected superficial vein1.
- Which vein is involved, and whether there is underlying venous reflux feeding it.
Your individual risk factors are considered alongside the scan: previous DVT or pulmonary embolism, active cancer, recent surgery or immobility, pregnancy or the postnatal period, hormone therapy, a known clotting disorder, and thrombosis occurring in a vein that is not varicose, which is a recognised warning sign.
Treatment
Treatment is decided from the scan findings and your risk factors, rather than from symptoms alone. Broadly, it falls into three groups.
Thrombosis within 3 cm of a deep vein junction. This is treated as though it were a deep vein thrombosis, with therapeutic anticoagulation, because the risk of extension into the deep system is high3.
Thrombosis at least 5 cm long and more than 3 cm from the junction. Current European guidance recommends a 45 day course of anticoagulation, most commonly fondaparinux 2.5 mg daily3. This is the group studied in the CALISTO trial, where treatment substantially reduced the risk of the thrombosis extending or progressing to deep vein thrombosis or pulmonary embolism1. Rivaroxaban has been shown to be a reasonable alternative for patients who cannot use injections2.
Short, localised thrombosis well away from the deep veins, in a patient without additional risk factors. Symptomatic treatment is usually sufficient: an anti-inflammatory such as ibuprofen if it suits you, a compression stocking, and continuing to walk and go about normal activity. Bed rest is not advised. If you take any anticoagulant or antiplatelet medication, tell us and do not stop it without instruction from the doctor who prescribed it.
Whichever group you fall into, we arrange a repeat scan where appropriate, because a thrombosis can extend during the first week or two. Any increase in pain, redness or swelling, or new swelling of the whole leg, should be reported rather than waited out.
Where the thrombosis has occurred in a varicose vein, treating the underlying venous reflux once the acute episode has settled reduces the chance of it happening again. That is usually done several weeks later, after a further scan.
Prevention
Superficial vein thrombosis is a recognised complication of varicose veins, and stagnant flow in a varicose vein is what predisposes it to clot. Treating the underlying varicose veins therefore reduces the likelihood of a further episode. If you have had one episode of phlebitis in a varicose vein, that is a reasonable prompt to have the veins assessed. See our page on varicose veins.
References
- Decousus H, Prandoni P, Mismetti P, et al; CALISTO Study Group. Fondaparinux for the treatment of superficial-vein thrombosis in the legs. N Engl J Med. 2010;363(13):1222–32. NEJM
- Beyer-Westendorf J, Schellong SM, Gerlach H, et al; SURPRISE investigators. Prevention of thromboembolic complications in patients with superficial-vein thrombosis given rivaroxaban or fondaparinux: the open-label, randomised, non-inferiority SURPRISE phase 3b trial. Lancet Haematol. 2017;4(3):e105–13. Lancet Haematology
- Kakkos SK, Gohel M, Baekgaard N, et al. European Society for Vascular Surgery (ESVS) 2021 clinical practice guidelines on the management of venous thrombosis. Eur J Vasc Endovasc Surg. 2021;61(1):9–82. PubMed 33334670
- De Maeseneer MG, Kakkos SK, Aherne T, et al. European Society for Vascular Surgery (ESVS) 2022 clinical practice guidelines on the management of chronic venous disease of the lower limbs. Eur J Vasc Endovasc Surg. 2022;63(2):184–267. ESVS guideline
Written and medically reviewed by Dr Johan Blignaut, MBChB (UOFS), FCS(SA), Specialist Surgeon.
Last medically reviewed: August 2026. This page is reviewed periodically and updated when clinical practice changes. It is general information, not medical advice – see our terms and medical disclaimer.