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Anatomy - Inferior Vena Cava

Discussion in 'Anatomy' started by Ghada Ali youssef, Jan 12, 2017.

  1. Ghada Ali youssef

    Ghada Ali youssef Golden Member

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    The inferior vena cava (IVC) is the largest vein in the body. It runs alongside the abdominal aorta, but there are several important differences between their branches and tributaries which make perfect fodder for trick questions in exams! I hope you find this anatomy guide helpful.

    The IVC in a nutshell
    • the IVC is formed by the union of the right and left common iliac veins
    • it conveys systemic venous blood from the lower limbs andpelvis, the undersurface of the diaphragm and parts of the abdominal wall –it does NOT drain blood from the gut!
    • it begins in the abdomen at L5 and ends in the thorax at T8, where it enters the pericardial sac and drains directly into the right atrium of the heart
    • it enters the abdomen through the caval opening of the diaphragm, which is located in its central tendon at vertebral level T8
    • it is accompanied through the caval opening by the terminal branches of the right phrenic nerve
    • the caval opening increases in size during inspiration, which encourages venous return of blood to the heart through the IVC
    • it is located on the posterior abdominal wall in the retroperitoneal space of the abdomen
    • it descends to the right of the abdominal aorta and the vertebral column
    • because it is situated to the right of the midline, left-sided veinsare longer than their equivalents coming from the right, as they have further to travel. This means that, for example, the left renal vein is longerthan the right.
    • running parallel to the IVC on its left-hand side are the aorta and the cisterna chyli
    • running on its right-hand side are the right sympathetic trunk and right ureter
    • organs sitting directly in front of the IVC include the liver, duodenum and pancreas
    • it is also crossed anteriorly by the portal triad within the lower free edge of the lesser omentum, the right gonadal artery, and the right common iliac artery
    • important structures passing behind the IVC include the right renal artery and the azygos vein
    • the normal diameter of the IVC is 1.5-2.5cm – this varies depending on inspiration and expiration and also with the patient’s volume status. A diameter of <1cm indicates hypovolaemia, whereas >2.5cm suggests fluid overload.
    • as the central venous pressure is normally very low (5-10mmHg), IVC aneurysms are exceptionally rare. The low pressure instead makes it vulnerable to obstruction, which can be due to internal occlusion by thrombosis or a spreading cancer (“tumour thrombus”), or external compression by an aortic aneurysm, intra-abdominal malignancies, or a heavily pregnant uterus.
    • as with the abdominal aorta, trauma to the IVC tends to be catastrophic with rapid exsanguination
    Tributaries of IVC
    This diagram summarises the arrangement of the tributaries of the IVC:

    420722a2726f4211d0bef828927f335e.png

    There are several key points to take away from this diagram:
    • the IVC has 3 anterior visceral tributaries (three hepatic), 3 lateral visceral tributaries (suprarenal, renal, gonadal), 5 lateral abdominal wall tributaries (inferior phrenic and four lumbar) and 3 veins of origin (two common iliac and the median sacral)
    • the IVC does not drain blood from the gut. This has to pass through the portal vein into the liver, to allow removal of any contaminants and processing of the nutrients. The portal vein is formed by the union of the splenic vein and superior mesenteric vein behind the neck of the pancreas. It travels into the liver as part of the portal triad in the lower free edge of the lesser omentum. Once processed, venous blood passes back into the systemic circulation via the three hepatic veins.
    • the upper retrohepatic part of the IVC runs directly behind the liver, and is firmly bound to its posterior surface by strong connective tissue attachments
    • the lower part of the IVC runs parallel to the aorta on its right-hand side
    • unlike the three suprarenal arteries, there is only one suprarenal vein on each side
    • because the aorta is in the way, the left renal vein has to pass in front of it to get to the IVC. Other veins such as the left suprarenal vein and left gonadal vein also need to get across to the other side, so they join with the left renal vein and get a lift with it across the front of the aorta. The right suprarenal vein and right gonadal vein are already on the correct side of the body, so they can drain directly into the IVC as separate tributaries.
    • the left renal vein is a really useful landmark to find if you are given a posterior abdominal wall prosection to label in your exam. It is easy to identify, as it is the only large vein that crosses over the front of the aorta. Once you’ve found it, you have identified vertebral level L1. The coeliac artery and superior mesenteric artery will emerge from the front of the aorta above this point. The gonadal arteries will emerge just below it, and the inferior mesenteric artery will be a little further down. This should allow you to then confidently work out the remaining branches – hooray!
    • the gonadal veins (testicular in men and ovarian in women) are situated surprisingly high up in the abdomen, considering that the organs they drain are either dangling in the scrotum or way down in the pelvis. This is because during early fetal life, the gonads begin to develop up next to the kidneys before migrating downwards to their proper positions. They get their blood supply from where they started, not from where they end up.
    • the lumbar veins arise posteriorly and will not be easily visible on most anatomical prosections
    • the fifth lumbar veins on either side drain into the iliolumbar vein, which is a tributary of the internal iliac vein
    Real anatomy : Radiology
    It’s very difficult to find nice images of a normal healthy person’s IVC, as patients generally only have detailed vascular scans if there is something wrong. The images below all show an anatomically normal IVC affected by a commonly occurring andobvious disease process, but you should still be able to appreciate the overall arrangement of its branches and its relationships to the other structures in the retroperitoneal space. I’ve provided links to the case reports if you want to find out more.

    ebb072e8d4e12f117f67abcbb07dee1d.jpg
    Coronal CT scan showing massive IVC thrombosis secondary to caval stenosis following surgery for an orthotopic heart transplant – this is a rare but well-recognised complication

    82547066b5128e55d35eabdc78c9580d.gif
    Coronal CT scan showing a large right-sided renal cell carcinoma (white arrow) with significant extension along the IVC (black arrow). The aorta is visible as the bright white structure lying next to the IVC

    cf8ba65ae6c924f15fe08081c005cca3.jpg
    Coronal CT scan showing complete occlusionof the upper part of the IVC secondary to extension of a large hepatocellular carcinoma along the hepatic vein (A). This life-threatening complication was treated with endovascular stenting to reopen the vessel and restore blood flow (D).

    eeb3ba6b1a937cb9909d3a91480e3ac5.jpg
    Coronal CT scan showing IVC filter thrombosis. The IVC filter is visible as the pointy white lines crossing the lumen – these devices are used to treat patients with DVTs who are unsuitable for anticoagulation. They can sometimes be complicated, as in this case, by distal IVC thrombosis.

    Real Anatomy : Surgical
    This smashing little video from HenryFordTV on YouTube shows an IVC thrombectomy procedure to remove a large tumour thrombus from a spreading renal cell carcinoma. It’s done using the incredibly slick da Vinci robotic surgery system, which allows surgeons to perform major operations using minimal access techniques. The retroperitoneal space is opened and the IVC is mobilised by division of the lumbar veins. The IVC and left renal vein are clamped using Rommel tourniquets. The surgeon then splits open the IVC and carefully removes all the horrible tumour thrombus. The outcome for the patient was fantastic – he went home after 48 hours and had nothing but a few tiny scars.



    References
    • Larsen TR, Essad K, Jain SKA, et al; “An incidental mass in the inferior vena cava discovered on echocardiogram“, International Journal of Case Reports and Images 2012;3(12):58–61.
    • Netter FH; “Atlas of Human Anatomy, 5th Edition” – Elsevier Saunders 2010. This is in my opinion the absolute best anatomy atlas out there. The illustrations are lifelike, extremely accurate and weirdly beautiful. Plus the cover is shiny. It’s worth every penny.
    • Santise G, D’Ancona G, Baglini R et al; “Hybrid treatment of inferior vena cava obstruction after orthotopic heart transplantation“, Interactive Cardiovascular and Thoracic Surgery 2010;11:817-819
      Interact CardioVasc Thorac Surg 2010;11:817-819
    • Sinnatamby CS; “Last’s Anatomy, 12th Edition” – Churchill Livingstone 2011
    • Snell RS; “Clinical Anatomy by Regions, 9th Edition” – Lippincott Williams and Wilkins 2011
    • Xiao L, Tong J, Shen J; “Endoluminal treatment for venous vascular complications of malignant tumors“, Experimental and Therapeutic Medicine 2012;4(2):323-328
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