3The historyColonic embolization for LGI bleeding was attempt as early as the 1970s by Rosch and BrooksteinThe catheters and the embolic materials available then were primitive, and initial efforts led to unacceptably high rates of ischemia and infarction ranging from 13% to 33%The high rates of infarction in these early series were probably due to the relatively larger catheters ( F) used and more limited embolic agents (autologous clot and gelatine sponge)Throughout the 1980s, colonic embolization was generally abandoned in favor of vasopressin infusionRosch I, Dotter CT, Antonovic R. Selective vasoconstrictor infusion in the management of arteriocapillary gastrointestinal hemorrhage, AJR Radium Ther Nucl Med 1972
4The historyVasopressin infusion has important limitations including a failure rate greater than 20% and a rebleeding rate greater than 15%.It’s very labor intensive and time consuming due to management of an indwelling arterial catheter.Dissatisfaction with catheter directed vasocostriction led to renewed interest in embolization in the late 1980s and early 1990s when coaxial microcatheter become available.These catheters typically range in size from 2.5 to 3 F in diameter and can be advanced through a 5 F catheter
5LGI bleeding vasopressin versus embolization In the 70’ and 80’ vasopressin was the recommended therapy for LGI bleeding and embolotherapy was promoted for UGI bleeding.Since the 90’ there is a less clear anatomic delineation of where to apply these treatments
6Vasopressin infusionThe catheter just needs to be placed selectively into the main trunk of SMA or IMAThe devices are less complex than those for embolization: a single 5 F catheter is all the equipment requiredRarely, vasopressin infusion into a single vessel may fail to terminate bleeding if the lesion is near a junction of 2 arterial distributions, such as the splenic junction.In these cases, 2 catheters may be required to simultaneously infuse into SMA and IMA
7Vasopressin infusion first step Typical vasopressin therapy involves an initial 20-minute infusion at a rate of 0.2U/min followed by repeated arteriography to determine that bleeding has stopped and that the artery is not overconstrictedIf bleeding continues, the infusion may increase to 0.3 U/min and than 0.4U/min followed by a waiting period for the increased drug dose to take effect and than another arteriogram to assess the effectTHEREFORE, INTRAPROCEDURAL TIME MAY BE SIMILAR TO THAT FOR EMBOLIZATION
8Vasopressin infusion second step Vasopressin therapy requires a longer committment of catheter management. When the proper dose is determined, the vasopressin is infused at that rate for 6-12 hours.The dose is than reduced by half and the infusion is continued for another hours.The catheter is than removed if there are no clinical signs of bleeding but, at this time, the catheter has been in place for 1-2 days.Prolonged catheterization may also increase the risk of groin complication like hematoma or thrombosisDiverticularbleedingAfter 24 hoursof vasopressininfusion 0.1 U/min
9Vasopressin infusion general limitations ability to catheterize the main SMA and IMA trunkcoagulopathyatherosclerosis: atherosclerotic arteries do not constrict in response to vasopressin despite successful catheterization
10Vasopressin infusion success rate Vasopressin therapy is a particularly effective therapy when applied to LGI hemorrhageGeneral series of LGI bleeding with mixed locations (small bowel and colon) and varied etiologies report success rates ranging from 59% and 90%One study who segregated small bowel from colonic sources found a slightly better response in the colon at 83%, vs 71% in the small bowelPennoyer WP. Management of angiogram positive lower gastrointestinal hemorrhage: long term follow-up of non-operative treatments. Int J Colorectal Dis 1996
11Vasopressin infusion complications Vasopressin infusion is associated with major complications in 0-21% of cases and, in many as 9%, the results were fatalMinor complications are more common with reported frequency ranging from 10 to 41%puncture site complications: hematoma (7%)thrombosispseudoaneurysmspasmcatheter sepsiscomplications at the infusion catheter: thrombosisdissectionEckstein MRGastric bleeding: therapy with intraarterial vasopressin and transcatheter embolization, Radiology 1984
12Vasopressin infusion complications sistemic effect (21%): arrhythmiashypotensionanginacardiac arrestspontaneous bacterial peritonitisintestinal infarction: thrombosisend organ ischemia (overconstriction)Eckstein MR Gastric bleeding: therapy with intraarterial vasopressin and transcatheter embolization. Radiology 1984
13EmbolizationA conventional 5 F catheter may be used to select a first-order vessel (SMA or IMA)A microcatheter can be advanced through this catheter to more distal, smaller vesselsIn the mesenteric circulation, the marginal artery or vasa recta can be selectively catheterized very close to the site of bleeding. This has been termed SUPERSELECTIVE CATHETERIZATIONOnce the bleeding vessel has been superselectively catheterized, embolic material can be deployed to arrest hemorrhage.Superselective embolization limits the segment of bowel at risk for ischemia or most often obviate the risk altogether
14Choice of embolic material EmbolizationChoice of embolic materialspongostanautologous clotabsolute alcoholMontoya 2004detachable balloonscyanoacrylateCantasdemir 2003
15Choice of embolic material EmbolizationChoice of embolic materialPermanent embolic agent that incites an intraluminal thrombosis withan associated inflammatory reaction.PVA particles are supplied in different sizes from smaller than 100 mto 1000 m in diameterPOLYVINIL ALCOHOL (PVA)PVA may have advantages, particularly for embolization of tumors, because the agent will flow to the bleeding site and occlude numerous vessels from a single injection.However, the particles cannot be directly visualized, cannot be precisely deposited and less forgiving than microcoils if non-target embolization occurs.PolyVinilyl Alcool (Ivalon, Contour)
16Choice of embolic material EmbolizationChoice of embolic materialembospheres
17Choice of embolic material EmbolizationChoice of embolic materialMade of platinum or stainless steel, when deployed function in a similar manner to a surgical ligation. They are biocompatible but high thrombogenic due to addiction of sinthetic fibers attached to the coil.MICROCOILSKessaris Martin 2000Treiber Vignali 2004spirali
18Embolization with coils Microcoils seem to be better for treating colonic hemorrhage because they are easy to visualize with fluoroscopy and deploy accurately
19Mechanism of embolization Embolization decrease perfusion pressure enough to arrest hemorrhage but notto the extent of total devascularization.Due to the limited collateral blood flow in the colon, overly aggressive embolization must be avoided.The mechanism of embolization depends on the embolic agent used.Microcoils decrease perfusion pressure and induce local vasospasm.This enables the patient to more effectively form clot, leading to hemostasis.Superselective embolization limits the segment of bowel at risk for ischemia.
20Colo-rectal bleeding percutaneous embolization (17 pts) Two cases of transient bowel ischemiaNone developed infarction, peforation or strictureThese authors argue against the use of PVA as sole embolization agent.The reasoning in that the small particles may reach intramural circulation and thus occlude the submucosal plexus beyond the level of collateralization. Another advantage of coils is that they are visible and therefore more controllableEvangelista P, J Vasc Interv Radiol 2000
21Limitations of embolization The most important limitations of endovascular therapy is the inability to diagnoseand treat patients who are not actively bleeding.Embolization is morely treating a symptom of the underlying disorder than thedisease itself. Patients with multifocal disease are at risk for repeatedhemorrhage from other affected sites (11% and 19% in old and more recent series, respectively)Other limitations include the inability to perform superselective catheterization inpatients with difficult vascular anatomy or severe atherosclerotic diseaseDifferent disorders will vary in responsiveness to embolization.Angiodysplasia is more difficult to treat with embolization.
22Technical versus clinical success of embolization Technical successSuccessful delivery of embolizing agentAbsence of extravasation at completion angiographyClinical successTermination of bloody output from the bowelStabilization of hematocrit levelLack of further transfusionsClinical success rates are often slightly lower than technical success rates because bleeding can continue despite successful placement of emboli.This may be caused by collateral perfusion around the emboli or coagulopathy that prevents formation of thombus despite blockade of arterial flow.
24Complications of embolization In the colon, it’s probably best to place coils as far peripherally as possibleThe small intestine has a different vascular pattern with a more extensive collateral arcade in the bowel wall. This make the small bowel more resistant to infarction.The embolic material used can also affect the risk of infarction.Small embolic particles that occlude the arteries very peripherally (at the arteriolar level or beyond) increase the chance of infarction.For these reason microcoils and larger PVA particles are most commonly used.Overall (major and minor) intestinal ischemic complication rates in the modern series range from 0% to 70% (average 15%) with majority being minor complication, most of these not requiring any therapyFunaki B, Kostelic JK, Lorenz I et Al. Superselective microcoil embolization of colonic hemorrhage. AJR 2001
25Vasopressin versus embolization Most of literature on both consists of very small restrospective series with little or no control for anatomic location, lesion pathology or patient demographics and clinical characteristicsMost of vasopressin literature is older ( no combination with nitroglycerin to reduce complications)Single institutional series or controlled trials comparing these therapies are nearly nonexistent
26Vasopressin versus embolization Embolization has become a relatively safe option for treating LGI hemorrhageDespite more technically challenging, it has advantage of quicker completion of therapy, decreased recurrence of bleeding and some decreased complicationsChoice of therapy is institution-dependent, but where the expertise on both modalities exists, embolization is preferable
27conclusionsEndovascular treatment plays a definite role in controlling LGI bleedingVasopressin infusion seems to provoke higher rate of severe complicationsEmbolotherapy with superselective catheterization is currently the best endovascular modality of treatmentOperator skill is mandatory