Embolization procedures

Embolization with particulate matter was introduced in 1930 by Brooks for the treatment of a traumatic carotico-cavernous fistula with muscle fragments. Embolization therapy was later greatly influenced by the landmark paper by Nusbaum and Baum in 1963 who were able to demonstrate that bleeding rates as low as 0.5 ml per minute could be detected angiographically. This report was soon followed by transcatheter management, first using selective infusion of Vasopressin. Shortly thereafter in 1972 Roesch, Dotter and Brown reported control of acute gastric hemorrhage by embolization of the gastroepiploic artery using autologous clot. In the early 70s various embolic materials such as Gelfoam, polyvinyl akohal (Ivalon), the tissue adhesive Isobutyl Cyanoacrylate (Bucrylate) and detachable balloons were developed which, together with improvements in catheter technology, caused a tremendous upsurge of interest in embolization procedures (Fig. 47 chapter 15). In the mid 70s Gianturco and Wallace developed steel coils which today are one of the most widely used embolic materials. In 1981 Ellman et al. introduced absolute ethanol for tissue ablation and used it for infarction of kidneys. New technologies using minicatheters and microcoils have further facilitated the management of peripheral and neurovascular lesions.

Embolization for bleeding

Gastrointestinal bleeding can be effectively treated with interventional methods once the bleeding source has been demonstrated angiographically. Transcatheter treatment for GI bleeding includes pharmacologic agents for vasoconstriction such as Vasopressin (Pitressin) and embolic materials. Vasopressin is particularly indicated in acute gastritis and stress ulcers. With infusion into the left gastric artery bleeding may be stopped in up to 80% of cases. Peptic ulcers of the stomach and duodenum and diverticular disease of the colon can be successfully treated with selective intra-arterial infusion of Pitressin also. Alternatively GI bleeding can be arrested by embolotherapy with various temporarily or permanently occluding materials. Bleeding from lesions such as ulcers, erosions, diverticula, spontaneous leaks and traumatic tears requires embolization with temporarily occluding materials to get the patient through the acute episode which will permit vessel recanalization later so that perforation or stricture of bowel as well as organ function loss is minimised. Only if the bleeding site can be stopped right at its origin in the

periphery can small particles or microcoils be used (Fig. 8). Bleeding resulting from tumors, arteriovenous malformations and esophageal varices requires materials for permanent embolization such as Ivalon, coils, or tissue glues and ethanol.

For bleeding after trauma adequate angiographic assessment including CT for abdominal and pelvic injuries is necessary for optimal treatment in serious vascular trauma. Proper surgical care should not be delayed in the unstable patient in whom major vascular or organ injury is suspected. Embolization procedures should be considered particularly in conditions where surgical hemostasis is difficult such as in the thigh, the buttocks, the pelvis and the retroperitoneum. The catheter should be placed as selectively as possible for embolization to spare as much healthy tissue as possible. Steel coils are commonly used since they produce a fast and permanent occlusion. Alternatively, agents such as Gelfoam and Ivalon can be used.

Traumatic bleeding of organs such as kidney and liver often results from iatrogenic injuries secondary to punctures and biopsies which may result in AV-fistulas or false aneurysms. Such symptomatic lesions can be treated successfully by transcatheter embolization in a high percentage

using particulate matter especially coils and Ivalon, detachable balloons and tissue adhesives (Fig. 9). The choice between conservative management, transcatheter treatment and surgery in patients with non-iatrogenic trauma to abdominal organs is based on the clinical status. Laceration of organs with significant bleeding usually requires surgical revision.

Bleeding from arteriovenous malformations is treated with embolization as the primary method of choice. Correct selection of the appropriate embolization material (coils, detachable balloons, Ivalon, Bucrylate, ethanol) is mandatory to occlude the nidus of the lesion and not just the peripheral feeding arteries which would lead to rapid recurrence via collaterals.

Organ ablation and tumour embolization

Organ ablation by embolization for hypersplenism or renovascular hypertension in endstage kidney disease may be a valuable alternative to surgery. Total embolization of the spleen in one step however should be avoided because of the possible fatal complications from splenic

absesses or splenic rupture etc. Therefore only partial embolization of the spleen or embolization in multiple sessions have been advocated together with a meticulous aseptic technique and antibiotic therapy.

Tumor embolization may by carried out for acute bleeding from tumor vessels (bronchogenic carcinoma, renal tumors ), to reduce the blood supply to the tumor before Surgery (renal cell carcinoma) or to treat primary and secondary tumor manifestations (Fig. 10). Various protocols for embolization using Gelfoam, Ivalon, liquid polymers and ethanol to treat hepatocellular carcinoma and metastatic disease from colo-rectal and neuro-endocrine tumors have been developed. Chemo-embolisation, originally introduced in Japan, is being increasingly used in the D.S. and Europe to treat primary and secondary liver tumors as well as renal carcinoma. This technique uses a simultaneous combination of intra-arterial chemotherapy and peripheral embolizsation. Mitomycin C, Doxorubicin, 5-fluorouracil and Cisplatin have been used together with Gelfoam or Ivalon.

In pelvic malignancies embolisation serves mainly to treat bleeding by embolization of visceral branches of the hypogastric artery. Superselective catheterisation which confines the embolization to the vessels feeding the tumor is desirable.

Most complications encountered after organ embolization are grouped and known as the post-embolization syndrome. Fever and pain are the most prominent symptoms seen in almost every patient and usually lasting for two to seven days. Nausea and vomiting are seen in approximately 50% of the patients with embolization of the liver. Other possible complications are due to overspill or displacement of embolic material with damage to non-target areas.

Neuroembolization

Embolization procedures in the brain, head and neck and spinal cord have gained great importance since the first report of an embolization of a traumatic carotico-cavernous fistula by Brooks in 1930. With the development of detachable balloons and flow directed catheters for superselective catheterisation endovascular embolization of intra- and extracranial AV-malformations, angiomas and fistulas has become the primary method of treatment. Furthermore cerebral aneurysms not suite d to surgical clipping may be treated with detachable balloons and certain tumors (meningiomas, glomus tumors, angiofibromas) may be embolized pre-operatively with Bucrylate or Ivalon particles.

Christoph Zollikofer