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ECR 2018 / C-2499
Complications of vascular impingement in the median arcuate ligament syndrome
Congress: ECR 2018
Poster No.: C-2499
Type: Educational Exhibit
Keywords: Obstruction / Occlusion, Haemorrhage, Aneurysms, Embolisation, Complications, Arterial access, Ultrasound-Colour Doppler, Percutaneous, CT-Angiography, Vascular, Arteries / Aorta, Abdomen
Authors: S. Accogli, V. Napoli, M. Gabelloni, R. Cioni, D. Caramella; Pisa/IT

Findings and procedure details

 Digital subtraction angiography (DSA) is the reference imaging technique to diagnose CA stenosis due to compression by the MAL, revealing a characteristic superior indentation along the proximal CA about 5 mm from its origin11 (Fig. 4). During inspiration the compression is often lifted up and the indentation results less evident since abdominal viscera descend and CA has a more caudal orientation; conversely, impingement in MALS is more marked during expiration, even up to vessel occlusion, because of the superior displacement of the branches of the abdominal aorta relative to the crura. Compression is considered severe if it persists on end-inspiration and if post-stenotic dilatation and retrograde filling of the CA from the SMA and PD arcade are present11.

 Noninvasive diagnosis is based on CDUS and CT: CDUS has high sensitivity and allows differentiating MALS from coeliac artery stenosis by evaluation of peak-systolic velocity (PSV) which in MALS is  >200cm/s with aorta-CA ratio >3.0 during expiration, but normal during inspiration (Fig. 5). CT examination depicts a focal narrowing with “hooked” appearance in CA proximal part, given by the entrapment of the root of the CA by the crura of the diaphragm11 (Fig. 6). 

 Coeliac stenosis increases retrograde collateral blood flow from the SMA to the CA via the PD arcade, resulting in the hypertrophy of the vessels and true aneurysm formation. Many studies demonstrated that rheological changes in the wall flow-induced shear stress (WSS) may have a significant effect on the aneurysmal growth of arteries, because this frictional force is converted to biological signals via mechanoreceptors on endothelial cells,  modulating gene expression and the cellular function of the vessel walls12,13

True PDA aneurysms account for only 2% of all VAAs and almost half of true PDA aneurysms are associated with stenosis of CA, wich is compressed by the MAL 10-30% of cases14. DSA is the most useful diagnostic tool in determining the exact location of the aneurysm, the presence or absence of aneurysm rupture, and the haemodynamic changes caused by CA stenosis8, in particular retrograde blood flow in the PDA and gastroduodenal arteries (Fig. 7Fig. 8 e Fig. 9). 

 The majority of patients with PDA aneurysms present with life-threatening bleeding, therefore contemporary management is usually by emergency coil embolization7. A ruptured PDA aneurysm is diagnosed when a contrast enhanced CT scan reveals the presence of hematoma around a PDA aneurysm and around the head of the pancreas. The hematoma is mainly retroperitoneal, but sometimes the aneurysm may rupture into peritoneal cavity or the digestive tract14. When a peri-pancreatic hematoma is present but there is not a clear evidence of the presence of  an aneurysm, often due to compression of the aneurysm by the hematoma, an angiographic exam is performed, both to confirm the suspicion of aneurysm rupture and to stop the bleeding (Fig. 10Fig. 11 e  Fig. 12).

The first-line treatment of ruptured VAAs in otherwise stable patients is endovascular coiling and/or stent placement14,15 (Fig. 13). 

 Other well-established therapeutic options for MALS-associated aneurysms without rupture include open to laparoscopic surgical decompression of the ligament with or without surgical reconstruction or stenting, as well as the robot-assisted or endoscopic release. With the endovascular approach, some suggest to perform both embolization of the aneurysm coupled with recanalization of the celiac trunk. Others indicate coiling alone as enough treatment strategy, with no recurrence of bleeding on long-term follow-up (Fig. 14). However, the treatment protocol for PDA aneurysms is still debated2,16

 Timing the treatment of VAAs is controversial as some authors believe that aneurysms larger than 2 cm in diameter, those that show dimensional growing on follow-up imaging, and that are symptomatic, should be treated. Others suggest that the size of the VAAs, especially PDA aneurysms, does not seem to be related to the possibility of rupture and that they should be treated regardless of their size. It is not the absolute size (like in abdominal aortic aneurysms) but the relative size of the aneurysm to the originating vessel which increases the risk of rupture, in particular an aneurysm-to-artery ratio of at least 3 (range 3–10)2,8 (Fig. 15). 

 However, also patients who have small PDA aneurysms are at risk of acute rupture, and therefore observation alone may not be the best management strategy for such patients. In the literature, the mean size of the ruptured aneurysms is 9.5 mm and the smallest is only 2 mm, therefore all PDA aneurysms discovered by chance should be treated, regardless their size15. Thus the common management strategy for treatment of PDA aneurysm associated with CA stenosis due to compression by the MAL is transarterial embolization in the first instance, and surgical division of the MAL as early as possible, considering the patient’s condition11

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