Embolization
Encyclopedia
Embolization is a non-surgical, minimally-invasive procedure performed by an interventional radiologist and interventional neuroradiologists. It involves the selective occlusion
Vascular occlusion
Vascular occlusion is a sudden blockage of a blood vessel, usually with a clot. It differs from thrombosis in that it can be used to describe any form of blockage, not just one formed by a clot. When it occurs in a major vein, it can, in some cases, cause deep vein thrombosis. The condition is...

 of blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

s by purposely introducing emboli.

Therapeutic applications

Embolisation is used to treat a wide variety of conditions affecting different organs of the human body.

Hemorrhage

The treatment is used to occlude:
  • Arteriovenous malformation
    Arteriovenous malformation
    Arteriovenous malformation or AVM is an abnormal connection between veins and arteries, usually congenital. This pathology is widely known because of its occurrence in the central nervous system, but can appear in any location. An arteriovenous malformation is a vascular anomaly. It is a...

    s (AVMs)
  • Cerebral aneurysm
    Cerebral aneurysm
    A cerebral or brain aneurysm is a cerebrovascular disorder in which weakness in the wall of a cerebral artery or vein causes a localized dilation or ballooning of the blood vessel.- Signs and symptoms :...

  • Gastrointestinal bleeding
    Gastrointestinal bleeding
    Gastrointestinal bleeding or gastrointestinal hemorrhage describes every form of hemorrhage in the gastrointestinal tract, from the pharynx to the rectum. It has diverse causes, and a medical history, as well as physical examination, generally distinguishes between the main forms...

  • Epistaxis
  • Primary post-partum hemorrhage
  • Surgical hemorrhage
  • uterine fibroids
    Uterine fibroids
    A uterine fibroid is a benign tumor that originates from the smooth muscle layer and the accompanying connective tissue of the uterus.Fibroids are the most common benign tumors in...


Growths

The treatment is used to slow or stop blood supply thus reducing the size of the tumour:
  • Kidney lesions
  • Liver lesions, typically hepatocellular carcinoma
    Hepatocellular carcinoma
    Hepatocellular carcinoma is the most common type of liver cancer. Most cases of HCC are secondary to either a viral hepatitide infection or cirrhosis .Compared to other cancers, HCC is quite a rare tumor in the United States...

     (HCC). Treated either by particle infarction or transcatheter arterial chemoembolization
    Transcatheter arterial chemoembolization
    Transcatheter arterial chemoembolization / Transarterial Chemoembolization is a minimally invasive medical procedure to restrict a tumor's blood supply....

     (TACE).
  • Uterine fibroids

Procedure

The procedure is a minimally invasive alternative to surgery. The purpose of embolization is to prevent blood flow to an area of the body, which effectively can shrink a tumour or block an aneurysm.

The procedure is carried out as an endovascular procedure by a consultant radiologist in an interventional suite. It is common for most patients to have the treatment carried out with little or no sedation, although this depends largely on the organ to be embolized. Patients who undergo cerebral embolization or portal vein embolization are usually given a general anesthetic.

Access to the organ in question is acquired by means of a guidewire and catheter(s). Depending on the organ this can be very difficult and time consuming. The position of the correct artery or vein supplying the pathology in question is located by digital subtraction angiography
Digital subtraction angiography
Digital subtraction angiography is a type of fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a 'pre-contrast image' or the mask from later images, once...

 (DSA). These images are then used as a map for the radiologist to gain access to the correct vessel by selecting an appropriate catheter
Catheter
In medicine, a catheter is a tube that can be inserted into a body cavity, duct, or vessel. Catheters thereby allow drainage, administration of fluids or gases, or access by surgical instruments. The process of inserting a catheter is catheterization...

 and or wire, depending on the 'shape' of the surrounding anatomy.

Once in place, the treatment can begin. The artificial embolus used is usually one of the following:
  • Coils: Guglielmi Detachable Coil
    Guglielmi Detachable Coil
    A Guglielmi Detachable Coil, or GDC, is a platinum coil commonly used in intracranial non-invasive surgery for the occlusion of brain aneurysms. It was invented by Italian interventional neuroradiologist Dr...

     or Hydrocoil
  • Particles
  • Foam
  • Plug


Once the artificial emboli have been successfully introduced, another set of DSA images are taken to confirm a successful deployment.

Agents

Liquid embolic agents - Used for AVM, these agents are able to flow through complex vascular structures so the surgeon does not need to target his catheter to every single vessel. Onyx
Onyx (Interventional radiology)
In interventional radiology Onyx is a trade name for a copolymer uesd for embolisation therapy, which involves the occlusion of blood vessels. It is a liquid embolic agent. Onyx is produced and sold by ev3 Inc. - Components :...

 is an example for a liquid embolic agent.
  • nbca
    NBCA
    NBCA may refer to:* New Braunfels Christian Academy* New Brunswick Curling Association* Narrow Burst Cutting Area...

     - n-butyle-2-cyanoacrylate - This agent is a permanent rapidly acting liquid, similar to glues sold under trade names such as "SuperGlue," that will polymerize immediately upon contact with ions. It also undergoes an exothermic reaction which destroys the vessel wall. Since the polymerization is so rapid, it requires a skilled surgeon. During the procedure, the surgeon must flush the catheter before and after injecting the NBCA, or the agent will polymerize within the catheter. The catheter must also be withdrawn quickly or it will stick to the vessel. Oil can be mixed with NBCA to slow the rate of polymerization.

  • ethiodol - Made from iodine
    Iodine
    Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

     and poppyseed oil, this is a highly viscous agent. It is usually used for chemoembolizations, especially for hepatomas, since these tumors absorb iodine. The half life is five days, so it only temporarily embolizes vessels.


Sclerosing agents - These will harden the endothelial lining of vessels. They require more time to react than the liquid embolic agents. Therefore, they cannot be used for large or high-flow vessels.
  • ethanol
    Ethanol
    Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

     - This permanent agent is very good for treating AVM. The alcohol does need some time to denature proteins of the endothelium and activate the coagulation system to cause a blood clot. Therefore, some surgeons will use a balloon occlusion catheter to stop the blood flow and allow time for ethanol to work. Ethanol is toxic to the system in large quantities and may cause compartment syndrome. In addition, the injections are painful.

  • ethanolamine oleate - This permanent agent is used for sclerosing esophageal varices. It contains 2% benzyl alcohol, so it is less painful than ethanol. However it does cause hemolysis and renal failure in large doses.

  • sotradecol - This agent is used for superficial lower extremity varicose veins. It has been around for a very long time and is a proven remedy. However, it does cause hyperpigmentation of the region in 30% of patients. It is less painful than ethanol.


Particulate embolic agents - These are only used for precapillary arterioles or small arteries. These are also very good for AVM deep within the body. The disadvantage is that they are not easily targeted in the vessel. None of these are radioopaque, so they are difficult to view with radiologic imaging unless they are soaked in contrast prior to injection.
  • gelfoam - Temporarily occludes vessels for five weeks. Works by absorbing liquid and plugging the vessel. Composed of water-insoluble gelatin, so the particles may travel distally and occlude smaller capillaries. One way to localize the injection of gelfoam is to make a gelfoam sandwich. A coil is placed at a precise location, then gelfoam is injected and lodged into the coil.

  • polyvinyl alcohol
    Polyvinyl alcohol
    Polyvinyl alcohol is a water-soluble synthetic polymer .-Properties:...

     (PVA) - These are permanent agents. They are tiny balls 50-1200 um in size. The particles are not meant to mechanically occlude a vessel. Instead they cause an inflammatory reaction. Unfortunately, they have a tendency to clump together since the balls are not perfectly round. The clump can separate a few days later, failing as an embolic agent.

  • acrylic gelatin microspheres - These are superior permanent particulate embolic agents. They are similar to PVA, but are perfectly round, so they do not clump together. The balls are fragile, so they may crack inside small catheters.


Mechanical occlusion devices - These fit in all vessels. They also have the advantage of accuracy of location; they are deployed exactly where the catheter ends.
  • coils - These are used for AVF, aneurysms, or trauma
    Physical trauma
    Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...

    . They are very good for fast-flowing vessels because they immediately clot the vessel. made from platinum
    Platinum
    Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...

     or stainless
    Stainless
    Stainless may refer to:* Stainless steel, a corrosion-resistant metal alloy* Stainless Games, a British video game developer* Stainless Broadcasting Company, a TV broadcaster based in Michigan, US...

     steel. They induce clot due to the Dacron wool tails around the wire. The coil itself will not cause mechanical occlusion. Since it is made of metal, it is easily seen in radiographic images. The disadvantage is that large coils can disrupt the radiographic image. The coil may also lose its shape if the catheter is kinked. Also, there is a small risk of dislodging from the deployed location.

  • detachable balloon - Treats AVF and aneurysms. These balloons are simply implanted in a target vessel, then filled with saline through a one-way valve. The blood stops and endothelium grows around the balloon until the vessel fibroses. Unfortunately, the balloon may be hypertonic relative to blood and hence rupture and fail, or it may be hypotonic and shrink, migrating to a new location.

Advantages

  • Minimally invasive
  • No scarring
  • Minimal risk of infection
  • No or rare use of general anesthetic
  • Faster recovery time
  • High success rate compared to other procedures
  • Preserves fertility and anatomical integrity

Disadvantages

  • User dependent success rate
  • Risk of emboli reaching healthy tissue
  • Not suitable for everyone
  • Recurrence more likely

See also

  • Cerebral aneurysm
    Cerebral aneurysm
    A cerebral or brain aneurysm is a cerebrovascular disorder in which weakness in the wall of a cerebral artery or vein causes a localized dilation or ballooning of the blood vessel.- Signs and symptoms :...

  • Endovascular surgery
    Endovascular surgery
    Endovascular surgery is a form of minimally invasive surgery that was designed to access many regions of the body via major blood vessels.Endovascular techniques were originally designed for diagnostic purposes. Basic techniques involve the introduction of a catheter percutaneously into a large...

  • Gastrointestinal bleeding
    Gastrointestinal bleeding
    Gastrointestinal bleeding or gastrointestinal hemorrhage describes every form of hemorrhage in the gastrointestinal tract, from the pharynx to the rectum. It has diverse causes, and a medical history, as well as physical examination, generally distinguishes between the main forms...

  • Interventional radiology
    Interventional radiology
    Interventional radiology is a specialty of radiology, in which image-guided procedures are used to diagnose and treat a multitude of diseases across all body systems...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK