Asymptomatic Portomesenteric Venous Thrombosis After Colorectal Cancer Surgery: Incidence, Natural History, and Implications for Management.

BACKGROUND: Portomesenteric venous thrombosis (PMVT) after colorectal cancer (CRC) surgery is most often reported in symptomatic patients, leaving its frequency and natural history across the asymptomatic spectrum poorly defined. When encountered incidentally, it frequently prompts anticoagulation, hypercoagulability evaluation, or delays in oncologic treatment, despite limited evidence that intervention alters its course. Using a cohort with routine postoperative imaging, we characterized the incidence, anatomic distribution, risk factors, and clinical course of asymptomatic PMVT.

METHODS: We retrospectively studied 799 consecutive patients who underwent CRC surgery between April 2019 and June 2025. All patients underwent standardized abdominal computed tomography (CT) on postoperative day (POD) 6 as part of our institutional clinical pathway for immediate postoperative follow-up. PMVT was defined radiologically, and thrombus location was classified as peripheral intrahepatic branches or main portal/superior mesenteric vein. Management followed a risk-stratified pathway of therapeutic anticoagulation or active surveillance, with radiologic resolution assessed on follow-up CT. Given the limited number of events, multivariable analysis was considered exploratory.

RESULTS: Asymptomatic PMVT was identified in 33 patients (4.1%), none symptomatic at detection. Thrombi were predominantly confined to the distal intrahepatic branches. In exploratory multivariable analysis, age ≤ 60 years (OR 2.45, 95% CI 1.19-5.03, p = 0.015) and POD 5 WBC > 10 × 109/L (OR 2.39, 95% CI 1.16-4.93, p = 0.018) were independently associated with PMVT. Twenty-one patients received anticoagulation and 12 were managed with surveillance alone. Complete radiologic resolution occurred in all 33 patients within one year, including every patient managed without anticoagulation. Furthermore, there were no cases of thrombus extension, portal hypertension, or bowel ischemia.

CONCLUSION: When postoperative imaging is routinely performed, asymptomatic PMVT after CRC surgery is detected in approximately 4% of patients. It is typically confined to peripheral intrahepatic branches, and follows a uniformly benign self-limiting course, even in patients managed without anticoagulation. These findings argue against reflexive anticoagulation and extensive workup for short-segment, non-occlusive PMVT confined to peripheral intrahepatic branches, and support an individualized, predominantly conservative approach. We do not advocate routine postoperative CT; rather, surgeons who encounter incidental PMVT can be reassured regarding its favorable prognosis.