Answers

Short answers

1 The computed tomograms show a large ruptured aneurysm of the right internal iliac artery (large white arrow; figs 3 and 4) and an associated haematoma (white block arrow) that was palpable as a mass in the right iliac fossa. In addition, the patient has a large aneurysm of the left internal iliac artery (white dashed arrow).

View larger version (29K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 3 Abdominal computed tomogram; axial view. The large white arrow indicates the large ruptured aneurysm of the right internal iliac artery, the small white arrow the associated haematoma, and the white dashed arrow the large aneurysm of the left internal iliac artery

View larger version (52K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 4 Abdominal computed tomogram; coronal view. The large white arrow indicates the large ruptured aneurysm of the right internal iliac artery, the small white arrow the associated haematoma, and the white dashed arrow the large aneurysm of the left internal iliac artery. The blue arrow shows the normal abdominal aorta

2 Up to 40% of abdominal aortic aneurysms are associated with iliac aneurysms; therefore, it is important to ascertain if an abdominal aortic aneurysm is also present. Figure 4 shows that there is no associated abdominal aortic aneurysm (blue arrow).

3 The patient is showing the classic signs of hypovolaemic shock: normal temperature; tachycardia; and hypotension. The aim of treatment is to resuscitate the acutely ill patient and the ABC (airway, breathing, circulation) algorithm should be used; however, this approach should be tailored towards permissive hypotension and a systolic blood pressure of 80-100 mm Hg in the presence of a suspected ruptured aneurysm. In conjunction with resuscitation, rapid referral to a vascular surgeon or unit should be instigated.

4 Open surgical repair or endovascular repair are the definitive treatment options.

Long answers
1 Diagnosis
Isolated iliac artery aneurysms are relatively rare, with an estimated prevalence of 0.008-0.03%.^{1 2} Internal iliac artery aneurysms account for less than 20% of all isolated iliac aneurysms.³ Like abdominal aortic aneurysms, iliac artery aneurysms are most frequent in elderly men.^{4 5} The most common cause of aneurysms is atherosclerosis.⁵ Other causes include trauma, infection, dissection, excessive athletic effort (for example, bicycle racing), and connective tissue disorders such as Marfan syndrome and Ehlers-Danlos syndrome.⁶ Internal iliac artery aneurysms can also occur in women who have undergone pregnancy and delivery, in particular those who have had a traumatic birth, high forceps delivery, or caesarean section.⁷

Due to their position—deep within the pelvis—and their rare occurrence, internal iliac artery aneurysms are difficult to diagnose at an early stage. Their presence might only come to light with the onset of complications, such as urethral obstruction, haematuria, iliac vein thrombosis, large bowel obstruction, and lower extremity neurological deficit.^{8 9} Asymptomatic aneurysms are usually diagnosed incidentally at clinical examination or during imaging for other purposes. In most published surgical series, the average aneurysm size is 4-5 cm and the average size of a ruptured iliac artery aneurysm is 6 cm.¹⁰ The rate of rupture of internal iliac artery aneurysms has been reported to be as high as 67%, with an overall mortality of 71%.^{11 12} Repair is recommended for isolated iliac artery aneurysms greater than 3 cm in size.^{11 13 14}

2 Association with abdominal aortic aneurysms
Involvement of the iliac arteries is seen in up to 40% of patients with abdominal aortic aneurysms.¹⁵ Aorto-iliac aneurysms pose particular challenges compared with isolated aortic or iliac aneurysms.¹⁵ Concomitant aortic and iliac aneurysms are associated with an increased prevalence of cardiac, renal, and respiratory comorbidity, in addition to more complex anatomy.¹⁶

3 Resuscitation
Prompt diagnosis, ongoing resuscitation, and early definitive intervention provide the best chance of survival for patients presenting with any ruptured intra-abdominal aneurysm.¹⁷ The on-call vascular team must be involved at the earliest possible stage.

In the resuscitation room, the ABC (airway, breathing, circulation) algorithm detailed in the Advanced Trauma Life Support (ATLS) guidelines should be followed.¹⁸ In addition, any patient with a suspected leaking aneurysm should receive high flow oxygen along with continuous electrocardiogram and vital sign monitoring. Large bore intravenous access must be secured in the antecubital fossae and fluid resuscitation initiated. Group and cross match for at least six units of blood should be initiated as soon as possible.

Suspected ruptured abdominal aortic aneurysm is a common presentation in the accident and emergency department, and it is important to recognise the key features. The classic presentation is the triad of a palpable abdominal mass; sudden and severe abdominal pain, often radiating to the lower back; and hypotension.

Aggressive fluid resuscitation is the traditional approach to managing haemorrhagic shock. There is considerable evidence, however, that vigorous fluid resuscitation in patients with a ruptured aneurysm can exacerbate bleeding owing to clot disruption—from increased blood flow, increased perfusion pressure, and decreased blood viscosity—and dilutional coagulopathy.^{19 20 21}

The ideal target systolic blood pressure in patients with a ruptured aneurysm has yet to be identified. Current practice in trauma victims aims at maintaining a systolic pressure of 80 mm Hg.²² The ideal pressure will vary between patients and depends on their comorbidities. Decreased blood loss and increased survival have been demonstrated when patients are resuscitated to below normotensive blood pressures that still adequately perfuse vital organs until prompt and definitive control of haemorrhage is secured.²¹

4 Definitive treatment
Open surgery and endovascular approaches are the options for repair of iliac artery aneurysms in the elective or emergency setting. Ruptured aneurysms are usually treated with open surgery for rapid access and control of haemorrhage. Recent advances in endovascular catheter technology, transcatheter embolisation, and endovascular stent-graft placement, however, have made these strategies viable alternatives, both for elective and emergency repair.^{23 24}

Endovascular techniques are particularly useful when the abdomen is hostile because of previous surgery, stomas, radiation therapy, or obesity, and in patients with significant comorbidities.²⁵ Given the uncertain long-term durability of endovascular repairs and the potential need for secondary interventions, patients for endovascular repair should be selected carefully.^{26 27} Elective endovascular repair of iliac artery aneurysms is associated with a 1% mortality rate (range 0% to 4%).²⁵ The reported number of patients undergoing emergency endovascular treatment is ever increasing, and results are promising.^{28 29} Successful endovascular repair requires a good length of healthy artery distal to the aneurysm for stent positioning, which is often not the case as in many patients the internal iliac artery branches immediately beyond the aneurysm. Embolisation of the internal iliac artery and exclusion of common and external iliac aneurysms with covered stents are now common necessities.¹⁵ Unilateral and bilateral occlusion of the internal iliac arteries is associated with various complications, including buttock or thigh claudication, sexual dysfunction, colonic ischaemia, perineal necrosis, and acute limb ischaemia.¹⁵ The most common complication of endovascular treatment is a type I endoleak, which occurs in up to 7% of cases, of which 50% go on to rupture.^{30 31}

Open surgical techniques for iliac artery aneurysm include a lower abdominal retroperitoneal approach and simple interposition graft. When a patient has bilateral iliac artery aneurysms or aortic involvement, however, a transabdominal approach with aorto-iliac reconstruction is more versatile.³²

Cite this as: BMJ 2009;338:b2302