Review Articles

Background: Controversy persists as to whether all calf vein thrombi should be treated with anticoagulation or observed with duplex surveillance. We performed a systematic review of the literature to assess whether data could support either approach, followed by examination of its natural history by stratifying results according to early clot propagation, pulmonary emboli (PE), recurrence, and postthrombotic syndrome (PTS). Methods: Atotalof1513articleswere reviewedthatwerepublished fromJanuary1975toAugust2010usingcomputerizeddatabase searches of PubMed, Cochrane Controlled Trials Register, and extensive cross-references. English-language studies specifically examining calf deep vein thrombosis (C-DVT) defined as axial and/or muscular veins of the calf, not involving the popliteal vein, were included. Papers were independently reviewed by two investigators (E.M., F.L.) and quality graded based on nine methodologic standards reporting on four outcome parameters. Results: Of the 1513 citations reviewed, 31 relevant papers meeting predefined criteria were found: six randomized controlled trials (RCT) and 25 observational cohort studies or case series. There was a single RCT directly comparing anticoagulation with no anticoagulation with compression and duplex surveillance, and they found no difference in propagation, PE, or bleeding in a low-risk population. Based on two studies of moderately strong methodology, C-DVT propagation was reduced with anticoagulation. When treatment was unassigned, moderately strong evidence suggested that about 15% propagate to the popliteal vein or higher. However, based on nonrandomized data but with moderate to high quality (level A and B studies), propagation to popliteal or higher was 8% in those with no anticoagulation treated with surveillance only. Propagation involving adjacent calf veins but remaining in the calf occured in up to one-half of all those who propagate. Major bleeding was an intended endpoint in three RCTs and was reported as 0% to 6%, with a trend toward lower bleeding risk in more recent studies. PE during surveillance in studies with unassigned treatment was strikingly lower than the historical reports of PE recorded at presentation, emphasizing the distinction thatmustbemadebetweenthe twoentities.Recurrence inC-DVTis lower thanthighDVT,anddata suggest that in low-riskgroups with transient risk factors, 6 weeks of anticoagulation may be sufficient, as opposed to 12 weeks. Studies of PTS reported that patients with C-DVT had fewer symptoms than their thigh DVT counterparts. Approximately one out of 10 showed symptoms of CEAP Class 4 to 6; however, C5 or C6 with healed or active ulceration were not commonly encountered. Conclusions: No study of strong methodology could be found to resolve the controversy of optimal treatment of C-DVT. Given the risks of propagation, PE, and recurrence, the option of doing nothing should be considered unacceptable. In the absence of strong evidence to support anticoagulation over imaging surveillance with selective anticoagulation, either method of managing calf DVT must remain as current acceptable standards. (J Vasc Surg 2012;55:550-61.)