Aneurysmal Disease

Welcome to First Incision, the podcast about preparing for the General Surgery Fellowship exam. I'm your host, Amanda Nikolic. Let's get started with our team timeout. Our patient today is the arterial, venous and lymphatic module from the general surgical curriculum. And the operational topic we'll be covering today is aneurysmal disease. So to start with a couple of definitions. An aneurysm is dilatation of a blood vessel that is 50% more in size than the adjacent non-dilated vessel.

A true aneurysm involves all three layers of the vessel wall. So this includes the intima, media and adventitia. And a pseudoaneurysm is a defect in the arterial wall that results in extravascular hematoma that communicates with the vessel. Aneurysms can be classified according to their shape. And the two main shapes that are described are saccular, which is a discrete outpouching. And this can either be concentric or eccentric.

And the other shape that's described is a fusiform shape, which is circumferential dilatation.

Aneurysms can also be classified according to their anatomical location. And in this section of the curriculum, it seems to focus pretty heavily on abdominal aortic aneurysms. Aortic aneurysms can be described as infrarenal, of which more than 90% are. Juxtarenal, which means the aneurysm is extending up to the origins of the renal arteries.

Pararenal, which is where it involves the renal arteries, and suprarenal, where it extends above the renal arteries. They can also be visceral aneurysms, so blood vessels that supply viscera. And the common ones that we see are things like splenic artery aneurysms. And then they can also be peripheral, such as iliac and popliteal being two of the common ones. In terms of abdominal aortic aneurysms or AAAs, these are more common in men than in women and are more common with increasing age.

And patients who have abdominal aortic aneurysms have a high rate of coexisting popliteal or femoral aneurysms, so up to 25% of patients. So what is the pathogenesis of abdominal aortic aneurysms? The two most common etiological or causes of aneurysms are atherosclerotic plaques and hypertension. And the way that atherosclerotic plaques contribute to the development of aneurysms is by their contribution to

the destruction and degradation of elastin and collagen in the wall of the vessel. And the way they do this is that the macrophages in the atherosclerotic plaques secrete matrix metalloprotonases. which destroy elastin and collagen. And then this leads to loss of strength of the wall of the vessel and aneurysmal dilatation.

The way that hypertension contributes is that it causes luminal narrowing of the vasovasorum that supply the artery. And this leads to ischemia of the outer layers of the media, leading to degeneration, fibrosis. and cystic degeneration of the medial layer. Atherosclerotic plaques also cause thickening of the intima, which can also contribute to ischemia of the vessel wall.

Some other potential causes of aneurysms include external injury such as trauma, vasculitis with antibody-mediated damage and inflammation and necrosis of the vessel wall. infections, so mycotic aneurysms, where there's embolization of septic embolus, which cause a direct infection and damage to the arterial wall. And also syphilis can cause a type of obliterative end arteritis to the vasovasorum, which causes ischemic injury and aneurysmal dilatation.

And then rarer causes are problems with inadequate or abnormal collagen synthesis. So this is in patients with Marfan syndrome or type 4 Ehlers-Danlos where there's a defective type 3 collagen. Moving on to the risk factors for aneurysms and specifically AAAs, risk factors include increasing age, being a man, smoking, family history. And then all the other cardiovascular risk factors, so hypertension, hypercholesterolemia.

having peripheral vascular disease or strokes or AMIs, so vascular disease elsewhere, and having a known vascular aneurysm in another location.

So I wanted to spend a little bit of time talking about presentation and natural history of AAAs. So most AAAs are asymptomatic at diagnosis, but they can cause abdominal pain. tenderness or present with back pain. The potential complications that patients can experience from a AAA that might lead to their presentation include rupture. And this is where patients present with acute, severe abdominal or back pain and hypertension and shock.

Embolism, so they can flick off thrombus from within the aneurysm, which can embolize distally. So patients may present with trash foot or distal ischemia, or if the aneurysm is higher up, renal or bowel infarction. The aneurysm, it's very large, can also present with impingement on adjacent structures and present with obstruction, for example.

And it can also present with ischemia due to obstruction of a branch off the aorta and this causing distal ischemia. So for example, bowel, renal or lower limb ischemia. In terms of rupture, the... Natural history of a AAA is that on average, it will expand by 0.2 to 0.3 centimetres per year. And the risk of rupture is related to the size of the aneurysm.

So aneurysms that are less than three centimeters almost never rupture. The rate of rupture per year for a three to four centimeter aneurysm is about 0.5%. For a four to five centimeter is 1%. For a 5 to 6 is 3%, and for a 6 to 7 is 10%. And if it's more than 7 centimetres, the risk of rupture per year is 25%. Other factors that...

increase the risk of rupture include being a female because we are smaller, so it doesn't have to be quite as big before it might be significant and rupture. Patients who have higher blood pressures. patients who are current smokers and if the rate of expansion is more than half a centimetre per year or if the patient is symptomatic. And in terms of management of...

Triple A's. It's important to consider what the risk of rupture is compared to the risk of repairing the aneurysm. So the surgical mortality for elective repair of a AAA is somewhere around the 3% to 5% mark. It might be decreasing as operative techniques and management improve, but it's still not insignificant. So the time that we consider repairing a AAA is when the risk of rupture is higher than the risk of surgery.

And so in general, for an asymptomatic aneurysm, that's more than five and a half centimeters in men and more than five centimeters in women. For aneurysms that are rapidly expanding, so more than one centimetre in a year or more than seven millimetres in six months. And if the patient's fit for surgery, you would offer a operation or intervention.

And any patient with a symptomatic aneurysm should also be offered a repair. So that's aneurysms of any size that are painful or tender, those that are causing distal embolization. those that have signs of external compression, or obviously if it has ruptured. So let's talk about the management of a AAA. First thing is medical management and managing risk factors. So obviously you want to get the patient to stop smoking, get them to exercise, control their blood pressure, start them on a statin.

And any patient with an aneurysm should also be started on antiplatelet therapy, which both reduces their risk of cardiovascular morbidity, but also inhibits the thrombin formation within the aneurysm. And as I've mentioned, we would indicate surgery for aneurysms over five and a half centimetres or over five centimetres in women or those that are rapidly expanding or symptomatic.

But if you have a AAA that's less than five and a half centimeters in a man or less than five centimeter in a woman and is asymptomatic, then you put them on a surveillance program. And so surveillance typically will include ultrasound and the ultrasound... can be done at intervals according to the size of the aneurysm. So if it's less than four centimeters, you can do an ultrasound at 12 months. If it's more than four centimeters, you should be doing an ultrasound every six to 12 months.

And once that aneurysm is meeting that sort of five centimeter mark, you'd then be doing a CT angiogram. And the reason you do a CTA at this point is because ultrasound can underestimate the size of the aneurysm. And so it may put you over the... line for needing to intervene. And also CT angiogram is important for surgical planning or intervention planning. So talking about interventions.

The options include both endovascular and open operations. In terms of endovascular, essentially it involves accessing the femoral artery and inserting a graft. into the aorta that excludes the sac from the circulation. In order to do this procedure, there has to be favorable anatomy to take a graft. And so some of the things they talk about is that there needs to be a landing zone between the renal arteries and the start of the aneurysm sac.

That's at least one to one and a half centimeters for the proximal part of the graft to sit. And you can't have a lot of angulation at the proximal neck. There needs to be minimal tortuosity and also the iliofemoral vessels need to be adequate enough to place and insert large catheters. And if they're too tortuous, that may not be able to actually pass the catheters up into the aorta.

Obvious benefits of endovascular repair is a much shorter length of stay and a reduced mortality and morbidity from the initial operation. But saying that though, out to eight years, there's similar outcomes for EVA and open surgery, but EVA does have higher aneurysm recurrence rates at eight years. Some of the potential complications of EVAs or endovascular aortic repairs is ischemia, so to the limbs, spinal cord, kidneys.

bowel and peripheral, which can be because of blocking off vessels that are being relied upon as collaterals or can be because of distal embolization of atheroma. Obviously the puncture site can have complications such as bleeding and pseudoaneurysms. There can be stent malfunction including migration or thrombosis or occlusion and they can get infected.

Another complication they talk about with EVARS is what's called endoleak. And it's worth looking up a picture of the five different types of endoleaks. Essentially, type 1 is when there's inadequate sealing at either the proximal or distal part of the stent, and this allows blood to continue to pass into the aneurysm sac, and this needs immediate repair because this is a high-pressure system.

A type 2 leak is the commonest, and this is where you get retrograde filling of the sac from a patent branch off. of the aorta, usually the inferior mesenteric artery or a lumbar vessel. And most of these you would just observe as a number of them will spontaneously resolve. And if they don't and the sac continues to increase in size, then you can get the interventional radiologist to embolize the feeding vessel.

A type three is where there's a failure in the graft caused by a defect in the fabric or a disconnection of the overlap of the graft. And this also needs immediate repair. Type four is where there's... porosity in the actual graft itself so leaking of blood between the graft fabric which doesn't happen as much anymore due to new graft designs.

And type 5 is known as endotension, which is where the sac is growing, but you can't identify the source of the leak on imaging. And it's not really clear why these happen. In terms of other complications, something that commonly happens is a post-implantation fever, usually 7 to 10 days later, and it's thought to be secondary to thrombosis of the sac and an inflammatory reaction to that.

And for patients with EVARS, they do need follow-up imaging every 6 to 12 months with a CT, mostly to look for endoleak and for increasing size of the aneurysm sac. In terms of open AAA repair, the indications would be if an EVAR wasn't possible due to a hostile neck or angulation, if there's a suprarenal aneurysm.

A relative indication for open surgery is in younger patients because of that longer-term risk of recurrence being higher with the EVAs and in patients with connective tissue disorders. The principles...

are all that we'll really need to know for open operations, I think, because it's in our operative knows and not our operative does section of the curriculum. And essentially the principles are to safely access the retroperitoneum, usually through a midline laparotomy and mobilization of the small bowel to the right side of the patient. You need to secure both inflow and outflow, usually with clamp on the aorta and the common iliacs. You access the aneurysmal sac and...

control and secure any sites of potential back bleeding. So usually you'd ligate the IMA and then also oversow the lumbar vessels that drain into the posterior aspect of the sac. You then... Use your graft and do an end-to-end anastomosis of the graft using non-absorbable sutures. And then resect. excess sac and close the remnant of the sac over the graft. And so that's one of the differences between open and endovascular operations is that you actually excise the sac in an open operation.

Potential complications include bleeding, cardiovascular or respiratory complications, renal failure due to clamping, lower limb ischemia due to clamp time or... thrombosis or bits of aorta flicking off into the lower limbs, spinal cord ischemia, if you block off small vessels that the spinal cord is relying upon.

Ischemic colitis, which is one of the common things we get called for as general surgeons, given the patient's having the IMA ligated, if they don't have adequate collaterals, they can present with ischemia of the left colon and sigmoid.

The graft can get infected and again can occlude. So very briefly, I want to talk about ruptured AAA and also in the curriculum. talk a lot about management of concomitant abdominal pathology when you find a AAA, which I thought was an interesting thing they wanted us to focus on, but I will briefly talk about that too. So in terms of raptured AAA...

Overall, the mortality is up to 90%, with 75% of patients dying before they reach hospital. And of those that reach hospital, the in-hospital mortality is over 50%. And the clinical presentation is usually sudden onset of abdominal or back pain with circulatory collapse, and they may have a pulsatile abdominal mass. Patients who have free intraperitoneal rupture are usually have a fatal outcome due to lack of tamponade of the rupture.

And patients who have a contained retroperitoneal rupture are typically the ones that are going to make it to emergency surgery. The acute management is... hemostatic resuscitation with activation of the massive transfusion protocol, and permissive hypotension. And the treatment options... are actually EVA, so endovascular repair, if the patient's stable enough. And this is actually the preferred repair for a AAA, which I thought was quite surprising. Obviously, the patient...

might just be really unstable and crashing and you don't have another option. But if they have tamponaded and you can get them to an EVA, then that is preferable. And obviously if they're really unstable, then you need to do an open operation. The risk here is that when the patient has their anaesthetic, they lose their muscle tone, leading to a loss of the tamponade effect. And for these patients, you need to be prepped and draped prior to the patient even going off to sleep.

So then the other thing they talk about is management of concomitant abdominal pathology. So I think what they mean by this is if you're doing an elective aortic. repair and you find another pathology or you're doing an emergency AAA repair and you find intra-abdominal pathology or if you're working up

for a abdominal pathology and you find a triple A, what do you do and what's the sequence of treatment? So in general, if you're doing an elective aortic... repair and you have an incidental finding of asymptomatic non-vascular pathology, typically it's okay to proceed with an EVA because it's not really going to delay your treatment of the other pathology because there's rapid recovery.

If you're doing an open AAA repair, you need to think about the other pathology that you've found and whether you should delay the AAA repair to deal with that pathology. or if it's safe to wait and delay treatment of that other pathology until the patient's recovered from the AAA repair, with the last option being a simultaneous operation.

And the factors to consider is that if you're putting in an aortic graft and you have a bowel pathology, for example, if you open the bowel in the area of your wound, then there's a risk of graft infection. And also you will have to wait if you're doing an open repair for sort of six to eight weeks for the adhesions to mature before you can go back in there to deal with a second pathology. So the ones that I've heard of is that if you have a colon cancer,

what should you do first if you find AAA? And there's an interesting study out of the UK that looked at this and they found that there's quite a high rate of perioperative. AAA rupture post-abdominal surgery. operations. So the rate in this study of intraoperative or postoperative AAA rupture was 8.3% for patients who had a colon resection who had a concurrent AAA.

So actually their recommendation was if you can do the AAA repair with an EVAR and then wait two weeks and do your colorectal operation, that that would be ideal. But obviously if you have a symptomatic colorectal cancer, you'll have to treat the cancer first. then wait till they've recovered from that surgery to deal with their triple A.

If you have an emergent abdominal pathology and you incidentally find an aortic aneurysm, then you need to prioritize the most life-threatening pathology. So obviously, if you have a ruptured viscous, you deal with that and you come back and... Treat the triple A. And the other thing to consider is if you do a laparotomy for an acute abdomen and you find a pathology that might be due to the aneurysm, so they have an aneurysm and a negative laparotomy, so maybe their pain was because of the AAA.

or if you find small bowel ischemia, for example, then you need to get a vascular surgery consult intraoperatively. doing an elective abdominal operation and you incidentally find an aortic aneurysm, you can usually just proceed with the abdominal operation unless the aneurysm is very large or you can see retroperitoneal rupture or something like that.

And in this case, you would get a semi-urgent consult as they might need semi-urgent treatment with an EVAR or close follow-up and an elective repair. And that's it for aneurysmal disease. Please remember to rate, review and subscribe. I love reading your reviews and it makes it easier for others to find. It's time to close up.

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