Application of methylene blue solution injected through inferior mesenteric artery in lymph node detection after radical resection of rectal cancer

Interventions: Experimental group:Slowly and uniformly inject the methylene blue solution into the rectal cancer specimen through the open inferior mesenteric artery channel through the intravenous indwelling needle;Conrol group:Visual touch Primary outcome(s): The proportion of postoperative lymph node harvest greater than or equal to 12 Study Design: Parallel