Problem to be solved: to secure the liquid tightness between the two passages easily and reliably by dividing the blood discharge channel and the return flow path for the detainment needle used in the blood vessel for the purpose of dialysis treatment.Inserted into the vesselA hollow section discharge tube 2 for discharging blood in the blood vessel from the blood vessel to the outside of the blood vesselInserted into the vesselCombined with discharge tubeA retracting needle 1 is formed from a return pipe 3 having a hollow cross section for returning blood discharged from a blood vessel into a blood vesselThe outlet hole 2a is formed in the portion of the discharge tube 2 located in the blood vesselA discharge hole 2b is formed in a portion located outside the blood vessel of the discharge pipeAn inlet hole 3a is formed in a portion of the return pipe 3 located in the blood vesselA return hole 3b is formed in a portion of the return pipe 3 located outside the blood vessel.While stopping the outflow of blood from the outer end of the blood vessel to the outside end of the blood vessel outside the blood vessel side of the drain tube 2 and the return tube 3 through which the inner needle punching the blood vessel is inserted, the hemostatic valve allowing the insertion of the inner needle is brought into close contact with each other.Diagram【課題】透析治療等の目的で血管内に挿入された状態で使用される留置針の、血液の排出用流路と復帰用流路を区分する上で、両流路間の液密の確保を容易、且つ確実にする。【解決手段】血管内に挿入され、血管内の血液を血管から血管外へ排出させる中空断面の排出管２と、血管内に挿入され、排出管２に一体的に組み合わせられ、血管から排出された血液を血管内に復帰させる中空断面の復帰管３から留置針１を構成し、排出管２の血管内に位置する部分に流出孔２ａを、排出管２の血管外に位置する部分に排出孔２ｂを形成し、復帰管３の血管内に位置する部分に流入孔３ａを、復帰管３の血管外に位置する部分に復帰孔３ｂを形成する。血管を穿刺する内針が挿通する排出管２と復帰管３のいずれか一方の血管外の側に位置する外側端部の血管外側の端面に、血液の外側端部からの血管外への流出を阻止しながら、内針の挿通を許容する止血弁を密着させる。【選択図】図１
