Transarterial Embolisation

Transarterial embolisation is the deliberate occlusion of an artery or a vascular bed through a catheter, to stop bleeding, to cut off the blood supply to a tumour or malformation, or to shrink an organ.

The artery is accessed percutaneously (femoral, radial or brachial), a microcatheter is advanced selectively into the target vessel under fluoroscopic control after diagnostic angiography, and an embolic agent is delivered.

Agents include gelatin sponge (temporary, lasting days to weeks), polyvinyl alcohol particles and calibrated microspheres (permanent, 40 to 1200 micrometres), metal coils and plugs (proximal and distal occlusion of larger vessels), liquid agents (n-butyl cyanoacrylate glue, ethylene vinyl alcohol copolymer, absolute alcohol), covered stents for selected arterial injuries, and drug loaded or radioactive microspheres (chemoembolisation and radioembolisation) for liver tumours.

The choice depends on vessel size, desired duration, flow rate, and risk of non-target embolisation.

Embolisation is the first line treatment for many forms of arterial haemorrhage and a major option for hypervascular tumours. It controls bleeding in about 85 to 95% of cases (technical success over 95%, clinical success 70 to 90% depending on the site), and avoids surgery in the haemodynamically unstable and high risk patient.

Common indications are traumatic haemorrhage (pelvic, hepatic, splenic and renal), gastrointestinal bleeding after failed endoscopy, post-partum haemorrhage, haemoptysis, tumour treatment, fibroids, and prostate enlargement.

Indications.

• Haemorrhage: traumatic injury (pelvic fracture, solid organ injury with active extravasation or pseudoaneurysm), gastrointestinal bleeding (upper bleeding after failed endoscopic control, lower bleeding with localised extravasation), post-partum and post-operative haemorrhage, ruptured visceral or renal aneurysm, haemoptysis (bronchial and non-bronchial systemic arteries), epistaxis uncontrolled by packing, and iatrogenic injury (post-biopsy, post-nephrostomy bleeding).
• Tumour: hepatocellular carcinoma (transarterial chemoembolisation or radioembolisation), hypervascular liver metastases (neuroendocrine tumours), pre-operative embolisation of renal, bone, head and neck, meningioma and paraganglioma tumours, and palliation of symptomatic tumours.
• Uterine fibroids (uterine artery embolisation) and adenomyosis; benign prostatic hyperplasia (prostatic artery embolisation) in selected men; pelvic congestion.
• Vascular malformations: arteriovenous malformation, high flow fistula, and visceral aneurysm exclusion.
• Portal vein embolisation to induce liver hypertrophy before resection, splenic artery embolisation for hypersplenism, and renal embolisation for refractory haematuria or nephrectomy preparation.
• Treatment of endoleak after aneurysm stent grafting.

Contraindications. Absolute contraindications are few: uncorrected severe coagulopathy that cannot be reversed, a vessel that cannot be selectively catheterised, a target that cannot be isolated from vital organs (spinal, bowel or cerebral arteries), and severe contrast allergy not manageable.

Relative contraindications are renal impairment, active infection (risk of abscess in embolised tissue), poor liver function for liver embolisation (bilirubin over 3 mg in each dL or Child-Pugh C, portal vein occlusion), pregnancy (for elective procedures), and intolerance of general anaesthesia.

Preparation.

• Informed consent (urgent cases proceed after discussion where possible), with explanation of post-embolisation syndrome and the risk of ischaemic damage to non-target organs.
• Blood count, clotting, group and crossmatch, renal and liver function, and imaging (CT angiography to map the supply and plan access).
• Correction of coagulopathy where possible (platelets, plasma, vitamin K), resuscitation in haemorrhage, hydration, and antibiotic prophylaxis in selected procedures (liver chemoembolisation, uterine artery embolisation, prostate).
• Analgesia and antiemetics (post-embolisation pain is common), steroids in selected cases, and anaesthesia support as required.

Technique. After arterial access and diagnostic angiography of the bleeding or tumour territory, a microcatheter is placed selectively in the feeding branch beyond the origin of normal branches. Contrast injection confirms position and shows the flow dynamics and any shunts.

The embolic agent is delivered under continuous fluoroscopic observation (reflux of agent into non-target vessels is the main hazard), until flow stasis, a pruned tree appearance, or occlusion of the target. For bleeding, the aim is to occlude the vessel both distal and proximal to the bleeding point ("front door and back door") with coils or glue to prevent back filling by collaterals.

For tumours, the aim is stasis of the tumour feeders with preservation of normal tissue. Control angiography confirms the end point. Closure device or manual pressure is applied at the puncture site.

Findings.

• Pre-embolisation angiography: extravasation of contrast (a blush that grows through the series), pseudoaneurysm, arteriovenous fistula, cutoff of a vessel in trauma, tumour blush with tortuous feeding vessels and arteriovenous shunting, or a vascular nidus.
• Post-embolisation: loss of the blush or stasis in the target vessel, residual collateral flow (re-bleeding risk), and preserved flow to the normal organ.
• Technical failure: unable to select the vessel (spasm, tortuosity, dissection), non-target embolisation, or persistent bleeding from collaterals.
• Imaging response after tumour embolisation: devascularisation with lipiodol retention in hepatocellular carcinoma, reduced size on follow up, and non-enhancing necrosis on CT or MR.

Critical findings needing immediate action. Non-target embolisation with ischaemia (bowel infarction, limb ischaemia, spinal cord injury, stroke or retinal ischaemia from reflux into external carotid branches), persistent bleeding with instability (repeat angiography, alternate vessel, surgery), vessel perforation or dissection, groin haematoma or retroperitoneal bleeding,

contrast reaction, acute liver failure after liver embolisation, and sepsis or abscess in an embolised organ.

Complications. Post-embolisation syndrome (pain, fever, nausea and raised white cell count and liver enzymes in 20 to 80% of tumour and organ embolisations, settling in 3 to 7 days).

Non-target embolisation (bowel or gallbladder ischaemia, skin necrosis, pancreatitis, cranial nerve palsy, stroke, spinal ischaemia from bronchial or intercostal embolisation, gluteal claudication and bladder or rectal necrosis from pelvic embolisation).

Organ infarction and abscess (spleen, liver, kidney, uterus), with risk higher in biliary or portal disease; liver failure after chemoembolisation in poor liver reserve; contrast nephropathy; access complications (haematoma, pseudoaneurysm, dissection); coil migration; and ovarian failure after uterine artery embolisation (about 1 to 3%, higher over 45 years).

Re-bleeding occurs in 10 to 30% depending on the site and coagulopathy. Procedure related mortality is under 1% for elective and higher for emergencies.

Aftercare.

• Bed rest for 4 to 6 hours with observation of vital signs, puncture site, distal pulses, and urine output.
• Analgesia (opioids and non-steroidal agents), antiemetics, hydration, and antipyretics for post-embolisation syndrome; prophylactic or treatment antibiotics as indicated.
• Monitoring of haemoglobin, liver function, renal function, and lactate; repeat imaging for suspected re-bleeding or complications.
• Follow up CT or MR at 1 to 3 months for tumour response, and repeat sessions as needed; ultrasound or MR for fibroid volume.
• Return for fever lasting over a week, worsening pain, jaundice, bleeding, limb coldness, bowel symptoms, or neurological symptoms.

Special groups.

• Trauma patients: embolisation is combined with resuscitation, pelvic binder and damage control surgery; coagulopathy is corrected.
• Pregnancy and post-partum: uterine artery embolisation controls haemorrhage and preserves the uterus; foetal dose is considered in antenatal use.
• Cirrhosis: higher risk of liver failure and bleeding; treated at specialist centres.
• Children: tumour and malformation embolisation with general anaesthesia, small catheters and low contrast doses.
• Elderly and frail: embolisation is preferred over surgery for haemorrhage.
• Regions: trauma, post-partum haemorrhage, haemoptysis from tuberculosis, and hepatocellular carcinoma (hepatitis B related) are major indications; embolisation is often available in only a few referral centres.