The majority of aortic aneurysms are asymptomatic. However, some may become "symptomatic" [1] which usually manifests as mild abdominal or back pain. In the presence of a known aneurysm this often expedites repair for fear of impending rupture. However, alternate diagnoses should be considered, these include diverticular disease, cholecystitis and retroperitoneal inflammation.

We report a 70-year-old female presented with progressive epigastric and lower chest pain, which was subsequently confirmed to be due to acute mesenteric ischemia directly related to the unusual progressive thrombus load within her thoracoabdominal aortic aneurysm that was occluding the major branches.

A 70-year-old female was seen on clinic in May 2013 for an asymptomatic aortic aneurysm discovered incidentally. This type IV thoracoabdominal aortic aneurysm extended from the distal thoracic aorta to the aortic bifurcation measuring 6.1 cm in its maximal diameter. She had a past medical history of polymyalgia rheumatica (on low dose prednisolone), three previous duodenal ulcers which were treated non-operatively, osteoporosis and osteoarthritis. Echocardiogram and ECG were within normal limits.

She was worked up for elective open aortic repair as the aneurysm was not amenable to endovascular repair. However, one week prior to her planned surgery in August 2013, she was admitted under the cardiothoracic surgeons due to new and progressive epigastric and central lower chest pain radiating through to her back. She reported nausea, vomiting and anorexia. Clinical examination revealed normal observations. She had a clear chest on auscultation and there was a palpable aneurysm with local tenderness in the epigastric region. There was no evidence of peripheral vascular disease and all distal pulses were palpable. A FAST scan was performed in the emergency department on admission, which noted the aneurysm, but no free fluid to suggest any leak. Admission blood tests revealed mildly raised inflammatory markers (WCC 14.5 and CRP 18), other bloods were within normal limits. A computed tomograhpy (CT) scan angiography was booked and she was scheduled for the next elective list.

In hospital, her symptoms deteriorated over two days from admission and her abdominal pain was exacerbated by eating. A CT angiography was performed on the morning of her second day of admission revealing the aneurysm had grown to 6.5 cm in maximum diameter, but excluded rupture or dissection. However, there was evident occlusion of the superior mesenteric artery (SMA) and coeliac axis secondary to the mural thrombus lining the anterior aspect of the aneurysm (Figure 1).

Acute clinical deterioration occurred. Her lactate climbed to 6.3 from normal and she developed peritonitis, which was noted on the second night after admission. She was consented for an urgent exploratory laparotomy. At surgery, she was found to have irreversible bowel ischemia and an ischemic liver. A resection of the entire jejunum down to the ascending colon was completed. Retrograde revascularization was performed to both the superior mesenteric artery (SMA) and coeliac artery from her right common iliac artery using a long saphenous vein (Figure 2).

On intensive care she continued to deteriorate. She was palliated and died two days after the surgery.

This is the first case to report mesenteric ischemia as a result of organized aneurysm thrombus occluding the mesenteric visceral ostia. However, we suspect that this syndrome may well have occurred previously and labeled with an alternate diagnosis. This case raises a number of important issues related to misdiagnosis of "symptomatic" aneurysms, and gives new insight into the behaviour of aneurysm thrombus.

The majority of aneurysms are lined with thrombus. This thrombus is thought to be a key factor in aneurysm progression due to the inflammatory mediators released from it [2]. When it comes to repair aneurysms by endovascular means, it is generally recognized as a safe technique to use a branched or fenestrated graft to accommodate visceral branches in the abdomen [3]. Multilayered stents are now being developed, which uses the theory that thrombus formation invariably maintains visceral vessel perfusion, thus the patency of the stent allows blood flow into these branches without complex placement of fenestration or bespoke branches [4]. Distal embolization of intra-luminal thrombus is a well-recognized phenomenon. However, as we demonstrate in this case, the organized intra-luminal thrombus may occlude the visceral vessels causing mesenteric ischemia and death.

A patient with new abdominal pain and an unruptured abdominal aortic aneurysm should be considered very carefully. All alternate diagnoses unrelated to the aneurysm should be explored and common diseases such as cholecystitis or diverticulitis need to be excluded. This case highlights the fact that this search for an alternate diagnosis should be exhaustive and expedited including mesenteric ischemia. If diagnosis is delayed then irreversible bowel necrosis can occur in the presence of two treatable pathologies. It also demonstrates new insight into abnormal thrombus behavior and could impact on our theory behind new graft technology.

1. Haug ES, Romundstad P, Aadahl P, Myhre HO. Emergency non-ruptured abdominal aortic aneurysm. Eur J Vasc Endovasc Surg 2004 Dec;28(6):612–8.   [CrossRef]   [Pubmed]    
2. Michel JB, Martin-Ventura JL, Egido J, Novel aspects of the pathogenesis of aneurysms of the abdominal aorta in humans. FAD EU consortium. Cardiovasc Research 2011 Apr 1;90(1):18–27.   [CrossRef]   [Pubmed]    
3. Scali ST, Waterman A, Feezor RJ, et al. Treatment of acute visceral aortic pathology with fenestrated/branched endovascular repair in high-surgical-risk patients. J Vasc Surg 2013 Jul;58(1):56–65.   [CrossRef]   [Pubmed]    
4. Sultan S, Hynes N. One-year results of the multilayer flow modulator stent in the management of thoracoabdominal aortic aneurysms and type B dissections. J Endovasc Ther 2013 Jun;20(3):366–77.   [CrossRef]   [Pubmed]