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Sep 2, 2015

Deep venous thrombosis of the calf causes an undue amount of consternation. What's the best way to manage these?Anticoagulate, serial ultrasound, do nothing? We break down the evidence to help you decide.

What are we worried about with calf DVT?

  1. Will it become a PE?
  2. Will the clot propagate proximally?
  3. Does treatment make a difference for recurrence?
  4. Does treatment make a difference for post phlebitic syndrome?

The numbers

Propagation to proximal veins

  • Without anticoagulation: around 15%. Wide variation in numbers
  • Propagation with anticoagulation: around 2%
  • Propagation is probably higher with risk factors such as malignancy and an unprovoked clot
  • Caveat: isolated gastrocnemius and soleal vein clots progress at about 3% untreated. Felt to be lower risk than the other deep veins of the calf. Lower risk of extension. No clear evidence on what to do.

Pulmonary Embolism

  • Without anticoagulation up to 6%
  • With anticoagulation 0-6%, biggest study 3%, but PEs mostly asymptomatic 
  • 1 reported fatal PE, but unknown if this patient was anticoagulated


  • Short term recurrence without treatment: up to 30%
  • Short term treatment with treatment 0-3%,
  • Recurrence is higher if two calf veins involved, increased clot burden

Compression stockings and post thrombotic syndrome 

Post thrombotic syndrome (PTS) is a horrible consequence of DVT.  Reflux from valve injury and venous hypertension lead to chronic edema, pain, and leg ulcerations. If there’s something that can mitigate that in our patients, we’d want them to have it. The incidence of PTS  in proximal DVTs is around 50%, depending on the source you read. In calf DVTs, it’s lower: somewhere around 10 to 24%.

There is good evidence that compression stockings can decrease the incidence of PTS.

  • Lancet 1997: about 200 patients with acute DVT compression stockings versus none. Compression stockings reduced the rate of PTS by about 50%.
  • Annals of internal medicine 2004: Below the knee compression stockings to prevent the post thrombotic syndrome. Half of the patients with no compression stockings developed PTS versus a quarter who wore stockings. How long did they wear the stockings? 2 years. Why two years? It’s because that’s the time window when the majority of PTS develops. When you break down the numbers of the study, there was an NNT of 4. Treat four patients with compression stockings to prevent one post thrombotic syndrome. That is a huge return on investment. A frequent question: Do patients need to wear the stockings 24/7. The study protocols were said just during the day, so,... just during the day.

A 2014 Lancet study,  suggested that there was no benefit to compression stockings. The above two trials used stockings or no stockings, this one used the 30-40 mm Hg graduated compression stockings or placebo, which was a 5 mmHg stocking. Results: no benefit of compression stockings over placebo socks. Does this study show that stockings don't make a difference? Or was the placebo not actually a placebo since there was still some degree of compression, albeit light.  I think you could interpret all of this data in several ways.

  • First  - more recent data suggests compression stockings  don't work (although I disagree with that interpretation)
  • Second - there are several studies showing benefit with a low NNT... NNT of 4 for a horrible sequelae.
  • Third - a light grade of compression, such that was used in the recent Lancet stud,y gives the same result as high pressure compression.

ACCP recommends compression stockings for proximal DVTs (ankle pressure of 30-40 mm Hg). Start as soon as possible and continue for 2 years. That is a grade 1A recommendation. How this will change based on more recent evidence remains to be seen. Distal DVTs, even more unclear.

Duration of treatment

  • For proximal DVTs, 3 months of treatment but for calf DVTs, no benefit found if treatment extended beyond 6 weeks. 
  • The ACCP, American College of Chest Physicians, kind of recommends 6 weeks. Mostly of a discussion in the evidence review that there’s no benefit in treatment beyond 6 weeks.
  • Post surgical patients with 2 or more veins involved, 12 weeks (3 months of treatment)

Type of treatment

No superior agent. Unfractionated heparin, LMWH, vitamin K antagonists-nothing superior. Many providers are using oral Xa inhibitors, but these are unstudied (yet still heavily used). You can extrapolate that LMWH is aba inhibitor, albeit by a different mechanism, so an oral Xa inhibitor should be effective too, but we don’t have direct evidence to answer that question.

Different treatment recommendations and guidelines

2012 ACCP: serial ultrasound for low risk clots and treat high risk clots (cancer, close to the popliteal vein, history of prior DVT)

National Clinical Guideline Centre: did not mention the treatment of isolated distal DVT because the guideline “... focused on proximal DVT rather than isolated calf vein DVT as the latter is less likely to cause post thrombotic syndrome than proximal DVT and also less likely to embolize to the lungs."

International Consensus Statement on Prevention and Treatment of Venous Thromboembolism: 3 months of oral anticoagulants for all calf clots

Up to date: Treat for 3 months (based on poor evidence) versus 2 weeks of serial US

Hematologist Tom Deloughery

  • Muscular Calf Vein (soleus or gastrocnemius) Thrombosis: 10 days of therapeutic LMWH or rivaroxaban.  
  • Calf Vein Thrombosis: 6 weeks of rivaroxaban

Jeff Kline 3 weeks of rivaroxaban. Permanent anticoagulation for active cancer, unprovoked clot

Rob O: 6 weeks anticoagulant and 2 years compression stockings

References for this podcast

Links mentioned in this show