八鍬 恒芳

Tsuneyoshi YAKUWA

東邦大学医療センター大森病院臨床生理機能検査部

Department of Clinical Functional Physiology, Toho University Medical Center Omori Hospital

キーワード : venous hypertension, steal syndrome, vascular access, flow volume, duplex ultrasonography

バスキュラーアクセス（vascular access: VA）術後の合併症として，静脈高血圧症およびスチール症候群がある．静脈高血圧症とは，VAの灌流が様々な原因で障害されることで静脈のうっ滞が生じ，さらに側副路還流の発達が末梢側への逆行性灌流を形成して末梢組織からの静脈還流が阻害された状態である．超音波検査では，VAの上腕動脈血流量もしくは人工血管内血流量の低下や，静脈側の狭窄あるいは閉塞所見，過剰血流などの所見が得られる．スチール症候群は，VAの静脈側への血流量が増加することにより，本来灌流すべき上肢末梢への動脈血流が動静脈瘻により盗血されるために，前腕や手掌などで末梢循環障害および虚血症状を生じる病態をいう．超音波検査では過剰血流や動脈側の狭窄あるいは閉塞所見などの所見を確認できる．ただし，静脈高血圧症およびスチール症候群は，VAにおける血行動態の不均衡によって生じる病態であり，一定の特徴的な所見を呈することはないことに留意すべきである．そのため，症例ごとに症状も含めた全体的な評価が必要であり，超音波検査においても，より広範囲の観察を行うことで，形態と血流の評価から病態を把握することが重要である．

Complications after vascular access surgery include venous hypertension and dialysis access steal syndrome. Venous hypertension is venous stasis caused by impairment of vascular access perfusion due to various causes, and the development of collateral reflux further forms retrograde perfusion to the peripheral side, in which the venous perfusion is inhibited. In the ultrasound examination, findings such as decrease of brachial arterial blood flow rate or vascular graft flow rate in vascular access, stenosis or occlusion on the vein side, and excessive blood flow are obtained. Dialysis access steal syndrome is characterized by increased blood flow to the venous side of vascular access, and arteriovenous blood flow to the periphery of the upper extremity, which should be perfused, is stolen by an arteriovenous fistula, resulting in a condition that causes disorders and ischemic symptoms. Ultrasound examination can confirm findings such as excess blood flow and stenosis on the side of the artery or obstruction. It should be noted, however, that venous hypertension and dialysis access steal syndrome are conditions caused by an imbalance of arteriovenous perfusion in vascular access and do not exhibit certain characteristic findings. Therefore, overall evaluation including symptoms is necessary for each case, and it is important to grasp the disease state based on evaluation of the morphology and blood flow by conducting a wider range of observations during the ultrasound examination.