Streamline flow of the portal vein affects the lobar distribution of colorectal liver metastases and has a clinical impact on survival

PURPOSE: It is believed that blood from the superior mesenteric vein and splenic vein mixes incompletely in the portal vein and maintains a streamline flow influencing its anatomic distribution. Although several experimental studies have demonstrated the existence of streamlining, clinical studies have shown conflicting results. We investigated whether streamlining of portal vein affects the lobar distribution of colorectal liver metastases and estimated its impact on survival. METHODS: Data of patients who underwent hepatectomy for colorectal liver metastases were retrospectively collected. The chi-square test was used for analyzing the distribution of metastasis. Cox analysis was used to identify risk factors of survival. Fisher exact test was used for subgroup analysis comparing hepatic recurrence. RESULTS: A total of 410 patients were included. The right-to-left ratio of liver metastases were 2.20:1 in right-sided colon cancer and 1.39:1 in left-sided cancer (P = 0.017). Cox analyses showed that margin < 5 mm (P < 0.001; 95% confidence interval [CI], 1.648–4.884; hazard ratio [HR], 2.837), age ≥ 60 years (P = 0.004; 95% CI, 1.269–3.641; HR, 2.149), N2 status (P < 0.001, 95% CI, 1.598–4.215; HR, 2.595), tumor size ≥ 45 mm (P = 0.014; 95% CI, 1.159–3.758; HR, 2.087) and other metastasis (P = 0.012; 95% CI, 1.250–5.927; HR, 2.722) were risk factors of survival. However, in 70 patients who underwent right hemihepatectomy for solitary metastasis, left-sided colorectal cancer was a risk factor (P = 0.019; 95% CI, 1.293–17.956; HR, 4.818), and was associated with higher recurrence than right-sided cancer (43.1% and 15.8%, respectively, P = 0.049). CONCLUSION: This study showed significant difference in lobar distribution of liver metastases between right colon cancer and left colorecral cancer. Furthermore, survival of left-sided colorectal cancer was poorer than that of right-sided cancer in patients who underwent right hemihepatectomy for solitary metastasis. These findings can be helpful for clinicians planning treatment strategy.