Timing of symptomatic venous thromboembolism after surgery: meta-analysis

Br J Surg. 2023 Apr 12;110(5):553-561. doi: 10.1093/bjs/znad035.


Background: The timing at which venous thromboembolism (VTE) occurs after major surgery has major implications for the optimal duration of thromboprophylaxis. The aim of this study was to perform a systematic review and meta-analysis of the timing of postoperative VTE up to 4 weeks after surgery.

Methods: A systematic search of MEDLINE, Scopus, and CINAHL databases was performed between 1 January 2009 and 1 April 2022. Prospective studies that recruited patients who underwent a surgical procedure and reported at least 20 symptomatic, postoperative VTE events by time were included. Two reviewers independently selected studies according to the eligibility criteria, extracted data, and evaluated risk of bias. Data were analysed with a Poisson regression model, and the GRADE approach was used to rate the certainty of evidence.

Results: Some 6258 studies were evaluated, of which 22 (11 general, 5 urological, 4 mixed, and 2 orthopaedic postoperative surgical populations; total 1 864 875 patients and 24 927 VTE events) were eligible. Pooled evidence of moderate certainty showed that 47.1 per cent of the VTE events occurred during the first, 26.9 per cent during the second, 15.8 per cent during the third, and 10.1 per cent during the fourth week after surgery. The timing of VTE was consistent between individual studies.

Conclusion: Although nearly half of symptomatic VTE events in first 4 weeks occur during the first postoperative week, a substantial number of events occur several weeks after surgery. These data will inform clinicians and guideline developers about the duration of postoperative thromboprophylaxis.

Plain language summary

Hundreds of millions of surgical procedures are performed annually worldwide. Blood clots in legs and lungs represent serious, and sometimes fatal, complications of surgery. To prevent these complications, clinicians often give blood thinners to patients. To optimize the starting time and duration of use of blood thinners, it is crucial to know when blood clots occur after surgery. This study summarized the timing of blood clots after surgery based on a systematic review and meta-analysis of 22 prospective studies including thousands of patients with blood clots from various surgical fields. Of blood clots occurring within 4 weeks after surgery, 47 per cent occurred by the first, 74 per cent by the second, and 90 per cent by the third week after surgery. These research results are useful for patients, clinicians, and guideline developers to guide the starting time and duration of use of blood thinners after surgery.

Publication types

  • Systematic Review
  • Meta-Analysis

MeSH terms

  • Anticoagulants / therapeutic use
  • Humans
  • Prospective Studies
  • Venous Thromboembolism* / prevention & control


  • Anticoagulants