['Deep vein thrombosis (DVT) develops after major orthopedic surgery despite the current use of prophylaxis. DVT frequently develops in the soleal vein (SV) and might develop easily at the site of SV dilatation because of blood flow stasis. However, whether preoperative SV dilatation detected by ultrasonography predicts DVT after major orthopedic surgery remains unknown.', 'We examined whether SV dilatation detected by preoperative ultrasonography predicts DVT after major orthopedic surgery.', 'Ultrasonography was performed preoperatively and postoperatively in 243 patients with orthopedic diseases (mean age of 67±13 years, 77% women) who underwent total hip arthroplasty (THA, n=180) or total knee arthroplasty (TKA, n=63). Presence of DVT was diagnosed by ultrasonography and SV diameter ≥10mm was defined as SV dilatation. Patients with preoperative DVT were excluded.', 'Sixty-nine patients (28%) developed postoperative DVT. SV dilatation was found in 24 patients (10%), and 16 (67%) of those patients had postoperative DVT. Multivariate logistic regression analysis showed that female gender [odds ratio (OR): 4.09, p=0.004], TKA (OR: 2.52, p=0.011), and SV dilatation (OR: 6.67, p<0.001), but not presence of comorbidities, medications, or plasma d-dimer value, independently predict postoperative DVT. Subgroup analyses according to the operation site showed that female gender (OR: 3.27, p=0.043) and SV dilatation (OR: 3.72, p=0.022) were independent predictors of postoperative DVT in the THA group. SV dilatation (OR: 12.0, p=0.027) was an independent predictor of postoperative DVT also in the TKA group.'] Is soleal vein dilatation assessed by ultrasonography an independent predictor for deep vein thrombosis after major orthopedic surgery?