Conventional endovascular management techniques for SAA
Goal of endovascular treatment is to exclude aneursym while preserving splenic perfusion. Difficulties arise due the tortuosity of the splenic artery and that most lesions are located in the distal part of the splenic artery.
Direct coil embolisation
- Suitable for the management of true SAA with favourable anatomy eg. aneurysm neck <4mm.7 (Fig. 1)
- Dense coil packing of the aneurysm sac performed to promote thrombosis and occlusion.
Inflow and outflow coil embolisation
- Alternative strategy is exclusion of the inflow and outflow arterial segments to the aneurysm when the aneurysm morphology is not suitable for sac coil embolisation.
- Often used to manage splenic artery pseudoaneurysm due to lack of a structural wall within the sac.
- Coils are deployed distal and then proximal to the aneurysm to occlude inflow and outflow arterial supply. (Fig. 2)
- Prevents retrograde filling of aneurysm from collateral flow.
- Splenic perfusion is usually preserved provided collateral channels such as the pancreatica magna and dorsal pancreatic arteries are maintained.
Liquid embolic agents
- Useful in situations where the tortuosity of the splenic artery limits microcatheter access to the aneurysm or its distal outflow in the setting of an unfavourable aneurysm neck.
- Can be used to treat both true SAA (Fig. 3) and pseudoaneurysms (Fig. 4).
- Examples include n-butyl cyanoacrylate (NBCA) glue or ethylene vinyl alcohol co-polymer in dimethyl sulfoxide (Onyx; Medtronic, Dublin) and precipitating hydrophobic injectable liquid (PHIL, MicroVention, Tustin, CA) which are non-adhesive liquid embolic agents.
Stent-graft exclusion
- Used in the management of wide-necked aneurysms not suitable for coil embolisation.
- Excludes aneurysm while maintaining parent splenic artery patency.
- Generally used in larger and more proximal parts of the splenic artery.
- Limited by vessel tortuosity as stent-graft delivery systems may not readily track across tortuous anatomy.
- Risk of side branch occlusion (Fig. 5).
Advanced endovascular management techniques
Balloon assisted coil embolisation (BACE)
BACE is a technique that is used in the management of wide-necked cerebral aneurysms with a high success rate.8 Its use has been adapted in the management of wide-necked splenic artery aneurysms. The technique involves:
- Positioning of a microcatheter into the aneurysm
- A separate balloon catheter positioned across the neck of the aneurysm
- Inflation of the balloon catheter to temporarily occlude or remodel the aneurysm neck
- Deployment of detachable coils into the aneurysm
This technique allows a higher coil packing density to be achieved, reducing the risk of coil herniation and improving the rate of complete aneurysm sac occlusion.9
Stent assisted coil embolisation (SACE)
SACE is another vessel remodelling technique that is similar to BACE, used in the management of wide-necked SAA (Fig. 6) and also as a rescue procedure to reduce and prevent recurrent herniation of a previously placed coil.10 The technique can be performed via the 'jailing' approach:
- Microcatheter positioned within the aneurysm
- Deployment of permanent stent across the aneurysm neck
- Deployment of detachable coils into the aneurysm sac
or the 'coil-through' approach:
- Stent is deployed across the aneurysm
- Microcatheter is then passed through the strut of the stent and into the aneurysm
- Deployment of detachable coils into the aneurysm sac
Short term dual-antiplatelet therapy is often commenced post SACE to prevent in-stent thrombosis, which may be contraindicated in some patients.10
Temporary endovascular scaffold devices
These devices can be used in the management of wide-necked aneurysms and deployed using a similar technique to SACE. However, these devices can be retrieved after aneurysm coiling, avoiding the risk associated with permanent stents and the need for dual-antiplatelet therapy.7
Flow-diverting stents
Flow-diverters are high density, porous mesh stents designed as an alterative to stent-grafts while maintaining side branch and target artery patency.11 The design of the stent allows for the disruption of arterial inflow into the aneurysm sac, promoting thrombosis and gradual occlusion (Fig. 7).11 Benefits of flow-diverting stents include:
- Lower risk of intraprocedural aneurysm sac rupture
- Lower in profile with more flexible delivery systems (most designed for the neurovascular bed)
- High aneurysm sac occlusion rates
- Preservation of large side branch vessels
Splenic trauma management
- Low grade (grade I and II) injuries are often managed conservatively if haemodynamically stable with no other abdominal organ injuries.12
- High grade (grade III to V) injuries can be managed conservatively but is associated with higher failure rates. These injuries are now more commonly treated with splenic artery embolisation. Approximately 70% of grade III injuries are treated with embolisation.12
- Although grade V injuries can be managed with embolisation, it is associated with a high failure rate and operative management is recommended.13
- Operative management is indicated in haemodynamically unstable patients who are not fluid responsive regardless of AAST grading.12
Proximal splenic artery embolisation
- More commonly performed compared to distal embolisation.
- Preferred technique in high grade trauma with diffuse active bleeding to reduce perfusion pressure allowing for control of bleeding while maintaining splenic perfusion through collateral arteries (Fig. 8) and preserving splenic function.14
- Aim is to occlude mid splenic artery between pancreatica magna and dorsal pancreatic arteries to minimise risk of ischaemia by preserving collateral flow.14
- Collateral supply to the spleen generally involve the pancreatica magna, dorsal pancreatic and short gastric arteries (Fig. 9).
Distal splenic artery embolisation
- Indicated in isolated focal bleeds (Fig. 10).
- Associated with higher rate of minor complications (eg. splenic infarction, post procedural pain).
Partial splenic embolisation (PSE)
PSE can be used in the mangement of portal hypertension and as an alternative to a splenectomy in the mangement of hypersplenism.15 PSE can be performed using two different techniques which include:
- Proximal (non-selective) approach where embolic agents are injected into the main splenic artery causing randomised small infarcts throughout the spleen.15
- Distal (selective) approach where embolisation is performed by positioning a microcatheter in segmental branches (typically the lower pole branch) of the splenic artery.15