In addition to categorizing embolization procedures on the basis of their time course, embolization might be discussed according to the vessel or organ targeted. The discussion below focuses on organ-specific embolization procedures in the trauma patient. Blunt abdominal trauma as a cause of renal vascular injury is second only to penetrating trauma from stabbing and gunshot wounds. However, PSA might present acutely with mass effect, hematuria, or rupture with extracapsular hemorrhage.
Renal artery embolization in a year-old male, status post stab wound to the abdomen 6 days earlier. He presented with a decreasing hematocrit level and bleeding from his Foley catheter. A Selective left renal artery injection demonstrates a large pseudoaneurysm PSA arising from the lower lobe arterial distribution. Note also the early appearance of the renal vein, indicating a concomitant AVF. B Selective left renal artery injection following coil embolization of the lower lobe artery, demonstrating complete cessation of flow to the lower lobe arterial distribution.
Of import, note the persistent flow to the remainder of the kidney.
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C Unsubtracted image demonstrating the coil pack postembolization. Figure courtesy of Jan Durham, M. In addition to accidental trauma, renal embolization also might be helpful when treating iatrogenic renal injuries from percutaneous biopsy, nephrostomy, or nephrolithotomy. It is generally accepted that hemodynamically unstable patients with renal injuries—and all solid organ injuries with instability—will usually undergo immediate laporotomy. Most blunt renal injuries are diffuse capsular and parenchymal injuries; in a hemodynamically stable patient these most often are managed conservatively.
Contrast-enhanced CT is the accepted modality for the initial evaluation of suspected renal injury because of its high sensitivity and specificity. Excretory urography, which was commonly used in the past, is rarely used today. There is a trend toward obtaining angiography before surgery because this provides diagnostic information as well as possible definitive treatment, especially with penetrating injuries. Superselective embolization was performed wherever possible.
In a separate study, Hagiwara et al 20 demonstrated that of 21 patients with grade III or greater renal injury on CT, seven of eight patients with extravasation on angiography were successfully embolized. Furthermore, shock index heart rate divided by systolic blood pressure and average rate of fluid resuscitation improved significantly following embolization. Before the development of coaxial systems and microcatheters, superselective angiography and embolization were not possible.
As a result, more proximal embolization was performed, leading to increased renal parenchymal loss. Superselective technique is now the standard. Unlike splenic and hepatic arterial beds, renal arteries are end arteries and therefore occlusion of vessels proximal to the site of the injury will achieve hemostasis without retrograde bleeding.
Transcatheter Embolization and Therapy
Rarely, parenchymal enhancement can be seen from collateral capsular arterial branches; therefore, any embolization should be performed proximal to the origin of these vessels. Packing of a PSA neck, or sandwiching a PSA or AVF with proximal and distal control, is not required because of the end arterial supply of the kidney and lack of potential retrograde filling.
Traumatic injuries to the spleen often are amenable to embolization. Embolotherapy spares the patient a more invasive procedure and compared with splenectomy, targeted embolization saves tissue; it also spares the patient from the risks of postsplenectomy sepsis by maintaining splenic immune function Fig. As is the standard for other visceral injuries from blunt abdominal trauma, traumatic splenic injuries are commonly managed conservatively.
Generally speaking, hemodynamic stability dictates whether immediate surgery or expectant management with or without transarterial embolization will be the course of treatment. Contrast-enhanced spiral CT is an effective and accepted way of identifying splenic injuries and guiding the trauma team toward angiogram and possible embolization. However, the true value for identifying vascular injury or predicting surgical versus conservative management remains controversial.
Splenic embolization in a year-old unrestrained driver in a motor vehicle collision. A Contrast-enhanced computed tomography scan demonstrates a large splenic laceration and perisplenic hematoma with active contrast extravasation. B Selective splenic angiogram demonstrates active contrast extravasation from the proximal portion of the upper lobe artery.
C Postembolization angiogram demonstrates cessation of flow to the actively bleeding branch. Note the segmental perfusion abnormalities: Because of persistent bleeding, a single coil was placed in the proximal bleeding vessel. Note also the uncompromised perfusion to the lower lobe branch distribution. Grade I and II injures are managed conservatively.
The trauma team will use triage imaging and hemodynamic status of the patient to guide the decision for angiography. Angiography addresses the issue of acuity of perisplenic or subcapsular fluid collections identified on imaging studies. In two separate studies, Scalfani et al 8 and Hiagawara et al 9 have shown that splenic angiography can be used to diagnose and successfully embolize traumatic splenic vascular lesions with all grades of splenic injuries.
Although splenic injury severity was greatest in patients who ultimately required embolization in these studies, CT appearance did not predict angiographic findings. It is accepted that the likelihood of vascular injury increases with increasing splenic injury severity score. The vascular injuries sustained in the spleen are no different from those in other organs. The natural progression of untreated splenic PSA is not known. Although high splenic salvage rates are documented in the literature, the incidence of preservation of splenic function is not known.
As a result of this collateral flow, several options are available to the angiographer when considering splenic embolization. If diffuse bleeding is identified or suspected, selective distal embolization with Gelfoam may be performed with subsequent coil embolization of the proximal splenic artery. This combined embolization may help with oozing associated with this type injury 8 , 30 ; theoretically, decreasing the pressure head behind the injured vessel will lead to more timely hemostasis and has been performed routinely in several series. Hepatic injuries are common in blunt trauma. As with splenic and renal trauma, conservative management has become the standard of care, especially for blunt injuries.
As with most blunt abdominal traumatic injuries, contrast-enhanced CT usually demonstrates any significant hepatic injury. However, there is a paucity of information regarding the efficacy of CT in high-grade liver injuries. Extravasation of contrast during angiography is concordant with high-grade hepatic injuries, and these patients typically fail conservative management.
Deep parenchymal bleeding from complex traumatic liver injuries is often amenable to embolization rather than surgery 33 Fig. Furthermore, as with their splenic embolization study, the shock index, a common means of expressing hemodynamic stability in trauma patients, was significantly lower in these patients following embolization. This supports the role of early embolization in trauma patients, and may argue against the commonly held belief that all hemodynamically unstable patients should proceed to emergency laparotomy. Early embolization in blunt liver trauma also has been shown to decrease the volume of blood products and number of liver-related operations.
Blunt hepatic trauma in a year-old male status post motor vehicle collision, with liver laceration and diaphragmatic injury by initial computed tomography scan. The patient was initially treated conservatively. Seven days later, the patient went to the operating room for an emergency laparotomy due to bleeding from his liver laceration; packing failed to control the bleeding, and the patient was transferred emergently to the angiography suite. A Diagnostic angiogram of the common hepatic artery demonstrating contrast extravasation from one of the right hepatic artery branches.
Note the early bifurcation of the proper hepatic artery, with the left hepatic artery arising proximally. B Diagnostic angiogram of the right hepatic artery, early phase, demonstrating severe contrast extravasation from the proximal right hepatic artery. C Diagnostic angiogram of the right hepatic artery, late phase, showing large amount of contrast pooling from the proximal right hepatic arterial injury. D Postembolization angiogram demonstrating coil pack within the right hepatic artery. Gelfoam slurry failed to stop the extravasation. Figure courtesy of David Kumpe, M. The liver's dual blood supply allows for safe embolization of the hepatic artery.
Once patency of the portal vein is proven, embolization can be performed anywhere in the hepatic artery. If small particles are used, embolization is safest if performed distal to the origin of the cystic artery. Arterial embolization in trauma patients has not been proven effective for bile duct and venous injuries; however, tamponade within the organ tends to limit venous bleeding. The suspected cause of these delayed injuries is unique to the liver. Specifically, spillage of bile leads to inflammation that may damage adjacent vessels, subsequently leading to delayed bleeding. Traumatic vascular injury in the extremity is usually the result of a penetrating injury.
Direct blunt trauma can also cause extremity vascular injury, especially in the setting of fractures and joint dislocations. Angiography has been shown to be sensitive in detecting vascular injuries of the extremity. Unlike in visceral injury, physical examination has higher yield when evaluating the extremities. Hard clinical signs of vascular injury include active bleeding, diminished pulses, expanding or pulsatile hematoma, bruit or thrill, and evidence of peripheral ischemia.
As with other traumatic injuries, angiography with possible endovascular therapies has become an important factor in managing suspected extremity vascular injury. Major findings include occlusion, extravasation, PSA, and AVF; in addition, intraluminal filling defects such as thrombi and intimal flaps can also be visualized. Minor findings include luminal narrowing, focal widening of the lumen, arterial deviation, and slow flow that may be encountered in the calf because of high compartment pressures. As opposed to visceral injuries in which CT plays a major diagnostic role, physical examination is vital in the diagnosis of vascular injury in the extremity.
This is particularly true with injuries central to the hip or shoulder girdle. Noninvasive imaging techniques such as Doppler evaluation of vessels might be insensitive to extremity vascular injuries; it has been shown that Doppler interrogation can be falsely positive because of hemodynamic instability regardless of the presence vascular injury. Proximity injuries in the appendicular skeleton are controversial. In the current environment, proximity alone generally is not accepted as the sole criterion for angiography because of low yield on exploratory angiography and likely benign course of many clinically occult injuries.
Emergent surgical exploration is typically indicated in these patients. The principle of gaining proximal and distal control as close to the site of injury must be observed to minimize rebleeding from collateralization. Moreover, rapid hemostasis with minimal tissue compromise is the goal of therapy, and embolotherapy might prove impossible if the downstream organ cannot be embolized safely.
However, there are several differences regarding extremity trauma when compared with visceral embolization. Extravasation can only be embolized in nonvital branch vessels. Parallel arteries of the calf and forearm as well as nonaxial proximal arteries profunda femoral [PFA] and profunda brachial arteries can usually be embolized safely. Some injuries in main extremity arteries are amenable to percutaneous therapies and can be treated by the interventional radiologist. These injuries are more commonly being treated with endovascular covered stent placement that is beyond the scope of this discussion.
In addition, major bleeding vessels such as the femoral artery and the axillary artery can be temporized with an occlusion balloon as an aid to surgical intervention. When embolization is being considered, it is important to first document adequate collateral flow. Embolization is useful when surgically inaccessible actively bleeding vessels, such as the PFA, are identified. In young patients it is uniformly considered safe to sacrifice the PFA; in older patients, the PFA may represent the major vascular supply to the lower leg.
Permanent agents include metallic coils and embolization particles. Thrombin is used extensively for the treatment of iatrogenic access site PSA. Photograph shows components of the embolization table. Particles are mixed with contrast using a three-way stopcock. Gelfoam is one of the most commonly used agents in trauma. This gelatin sponge is a temporary agent derived from a biologic substance made of purified skin gelatin that has been used for many years as the primary embolization agent.
Gelfoam is also commonly used to provide relatively distal target embolization followed by more proximal embolization with coils. Gelfoam is also used after placement of coils to reinforce thrombosis, especially in patients with coagulopathy where coils alone may not provide vessel occlusion. Animal studies have shown that the peak foreign body reaction within a vessel can be reached after 20 days, with the cellular reaction disappearing by 45 days.
Gelfoam is available in a powder form with particle size of 40 to 60 um. Gelfoam powder provides a very distal capillary-level occlusion and it is not recommended in trauma applications. The most commonly used form is the sheet or block of Gelfoam that is cut with scissors in small 1- to 2-mm cubes that are then mixed with contrast medium in a 3- to 5-mL syringe using a three-way stopcock until a slurry is created Fig. When Gelfoam sheets are cut with scissors into cubes, the particles will have a size distribution ranging between and um.
Trauma in Interventional Radiology: Embolization in Trauma: Principles and Techniques
The compressed Gelfoam is then mixed with 3 to 5 mL of contrast using the stopcock and a second syringe. The resulting slurry is very concentrated, and usually smaller amounts are required to achieve vessel occlusion. The pumping method seems to produce smaller particles that are less uniform in size than the cutting method. If a microcatheter is used for particles or Gelfoam injection, a larger-lumen 0. Also, the stopcock can be place into a partially closed position to force the slurry into a more liquid form to prevent occlusion of the microcatheter lumen.
If the use of microcoils is also planned, the regular 0. Photographs of Gelfoam preparation steps. A The agent is cut into small cubes using sterile scissors. B The cubes are placed into a small cup to mix them with contrast. C The mixture is pumped using a three-way stopcock to create a slurry.
Principles of particle embolization are similar to Gelfoam; however, the main differences are that the sizes of the particles are more uniform and that particles produce a permanent occlusion of the vessel. Particles produce vessel occlusion by adherence to the wall, mechanical occlusion, and inflammatory reaction. The particles are prepared by mixing them with contrast material, usually by adding 5 mL of contrast to the 2- to 5-mL prefilled saline.
The air is carefully removed, and the syringe is gently inverted several times. Then, using a three-way stopcock attached to a smaller 1- to 5-mL syringe, the solution is further mixed Fig. The smaller syringe is used to inject small aliquots of the particles under careful fluoroscopic guidance. Constant agitation and remixing of the agent is very important to prevent particle aggregation. A higher-contrast material concentration usually results in precipitation of the particles with a higher tendency to conglomerate and form clusters.
The solution tends to become more stable with time, and premixing several minutes in advance is important. Adding saline makes the solution more homogeneous but visualization of the injections under fluoroscopy may be difficult especially in obese patients or when motion artifacts are present. PVA was originally used as a sponge sheet shaved into small fragments, then as noncalibrated particles that were not very uniform in caliber, and more recently as calibrated particles that are more uniform in size Contour SE Boston Scientific, Natick, MA.
Particle aggregation with occlusion of the hub of the catheter was a significant problem with the noncalibrated particles. Also, the extent of embolization appeared to be more diffuse with the noncalibrated particles because the produced aggregates caused more proximal embolization of larger vessels and remained occlusive over time. The particles are packaged in a mL syringe prefilled with 2 mL of normal saline.
A hydrophilic surface and uniformly spherical shape prevents aggregation. There are differences in the physical properties between the different types of spheres that may explain the different levels of occlusion of observed in vivo. Animal studies have shown that for the same size of particles, PVA spheres blocked significantly more distally in the vessels than TAGM spheres. PVA-based spheres Contour SE behave like a macroporous sponge that releases water under compression, and Embospheres or Bead Block spheres act as polymeric hydrogels that can be deformed without releasing water.
Embozene microspheres are newer particles CeloNova Biosciences, Newnan, GA made of a hydrogel core covered with a Polyzene agent that helps lubricate the surface and have high compressibility. Each size is color coded. They are available in close range of sizes: In theory, there is less tendency to clump, aggregate, or cause catheter occlusion. Further clinical studies are needed to evaluate if these narrow-range particles have significant advantages over the conventional spheres.
Quadra spheres are polyvinyl alcohol sodium acrylate spheres Biosphere Medical that expand to 4 times their dry-state diameter within 10 minutes when in contact with blood, nonionic contrast medium, or saline solution. In theory, the sphere expansion allows for secondary conformability to the vessel architecture, resulting in an increase in surface area contact for a more complete vessel occlusion. These particles have been used for drug delivery and uterine fibroid embolization; experience in trauma is currently limited. The use of liquid agents is limited in trauma.
Absolute alcohol or other sclerosing agents are not used in trauma due to the potential for tissue necrosis. They have been used successfully in the treatment of selected trauma patients with coagulopathy. The disadvantages of n-butyl cyanoacrylate and ethylene vinyl alcohol copolymer include the excessive cost of these agents and the need for extensive experience by the operator to prevent serious complications.
Thrombin has been used extensively for the treatment of femoral iatrogenic PSA after catheterization. It is derived from bovine thrombin with the rare potential of allergic reactions. Thrombin directly activates fibrinogen and converts it into fibrin monomers. Being a liquid agent, there is the potential for accidental distal embolization with serious consequences.
Main uses in trauma include the percutaneous treatment of postcatheterization PSA and the direct percutaneous puncture and embolization of peripheral PSA where the catheterization of the parent vessels is impossible. It has been successfully used in the treatment of traumatic PSA of the liver, spleen, lower extremities Fig.
Thrombin is used a liquid agent usually in a dilution of in 1 mL, injecting a small volume until thrombosis of the PSA is seen. At times, thrombin is combined with collagen for a more viscous and stable solution. Patient with a stab wound to the liver resulting in hemobilia. A Angiogram shows a large pseudoaneurysm PSA of a replaced left hepatic artery arrow. Superselective catheterization was not possible due to severe spasm of the vessels. Percutaneous puncture with injection of thrombin under ultrasound guidance was performed.
B Duplex ultrasound demonstrates flow in the PSA. C Duplex ultrasound after thrombin injection shows thrombosis of the PSA. D Angiogram after the embolization shows no filling of the PSA.
Transcatheter Arterial Embolization in the Trauma Patient: A Review
A coil is basically a piece of wire that is looped in different shapes and sizes. Coils provide a frame for clot formation and have the addition of some fibers made of wool, nylon fibers, polyester, silk to increase thrombogenicity. Bare coils require relatively dense packing to produce vessel occlusion. Coils are made of steel or platinum. Platinum is more expensive but is very radiopaque and more malleable than steel. Coils are available in multiple configurations. For trauma embolization, the main types of coils used are the macrocoils in 0.
Microcoils are inserted through microcatheters usually with a 0. Most of the coils are deployed by pushing them with a wire or a special wire pusher pushable coils. Other coils have some mechanism with controlled deployment that allows reposition before final release of the coil detachable coils. A Digital subtraction angiogram shows a pseudoaneurysm PSA with arteriovenous fistula of the anterior trunk of the left hypogastric; note the draining vein arrow. B Radiograph shows a misplaced coil protruding into the common iliac artery due to coil oversizing.
A snare is also shown in an attempt to remove the coil that resulted in coil migration. C Radiograph shows the migrated coil being removed with the snare from the left common femoral artery. Part of a second coil was also protruding into the iliac artery. A noncovered stent was placed over the coil in the common-external iliac artery. D Digital subtraction angiogram shows successful exclusion of the PSA.
Patient with a large left renal artery arteriovenous fistula AVF after a nephrectomy. A Angiogram shows an AVF of the stump of the left renal artery. B Selective left renal digital subtraction angiogram shows rapid filling of the left renal vein. C Digital subtraction angiogram venogram shows an occlusion balloon placed in the left renal vein to decrease flow and prevent coil migration. D Digital subtraction angiogram after embolization shows successful exclusion of the AVF. Patient with a massive long-standing renal arteriovenous fistula AVF that resulted in heart failure.
A Digital subtraction angiogram shows large AVF massive dilatation of the renal vein. B Access was obtained in the arterial and venous systems. An Amplatzer plug was placed through the venous system arrow in the exact location of the fistula. C Radiograph shows multiple coils were placed inside the plug arrow to increase thrombosis.
D Digital subtraction angiogram after embolization shows successful exclusion of the fistula. Note that the renal artery branches are now seen. Case courtesy of Barth Dolmatch, M. Detachable coils allow very precise deployment and embolization of different-sized vessels. The main advantage is that in case of initial misplacement, they can be retrieved.
Disadvantages include that the setup takes more time and they are significantly more expensive. These coils were originally designed for the treatment of cerebral aneurysms; some of the manufacturers have developed similar versions for the peripheral use that are less expensive. These coils are mainly used for the embolization of vessels that are very close to parent vessels where very precise positioning is required.
Amplatzer vascular plugs AVPs are occlusion devices derived from septal occluders used in cardiology. A guiding catheter or sheath is placed in position, and the plug is deployed by unsheathing it. The device can be resheathed if not in satisfactory position, and the plug is released by rotating the delivery wire counterclockwise. The main uses in trauma include the occlusion of relatively large vessels such the splenic artery, the renal artery, and peripheral AVF where using regular coils have the risk of accidental embolization Fig.
The main disadvantage of the AVP is that the device is relatively stiff compared with regular coils, and placing the guiding catheter or sheath inside tortuous vessels can be very difficult. Successful plug deployment into the target area may require using of triaxial system and additional manipulation.
The first-generation AVP devices have diameters from 4 to 16 mm using 5- to 8-French sheaths. The second-generation AVP II devices have a three-disk configuration, which includes additional thinner disks attached at the ends of the plugs for additional cross-sectional material. These newer plugs are more thrombogenic. Although not embolization agents, covered stents can provide life- and limb-saving vascular hemostatis while keeping the vessel lumen patent.
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Covered stents allow treatment of PSA, AVF, and other injuries in the renal, iliac, subclavian, and axillary arteries and other nonexpendable vessels 14 , 15 , 16 Fig. Custom-made devices were originally created by attaching a piece of saphenous vein or surgical graft over a bare metal stent. There are now several commercially available stent grafts.
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However, the use of metallic stents in trauma is not an approved indication, and it is an off-label applications of the stents that are marketed and FDA approved for biliary or tracheobronchial use. Potential complications of covered stent placement include stent occlusion, deformation and kinking, and loss of vessel branches after stent placement.
Although rare, covered stents have also the potential of getting infected in case of bacteremia and sepsis. The use of large introducer sheaths and the cost of these devices are also a major drawback of the use of covered stents in trauma. Adequate sizing is also critical with stent grafts. Embolization and Endovascular Management. Review Text From the reviews: With a list of contributors It's well-written and well-thought-out with clear layout and relevant figures It's comprehensive, written with an accessible, almost conversational style.
This is highly recommended to interventionalists both new and old. Review quote From the reviews: Bereits mit 17 erlitt er einen ersten Zusammenbruch, dessen Ursachen mehrere Jahre lang unbehandelt blieben. Er studierte erfolgreich Medizin und arbeitete als Hausarzt, bevor er an schubweiser paranoider Schizophrenie erkrankte. Er ist unter anderem aktiv bei den East End outsider poets und der Survivors Poetry.
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