I. Etiology The common causes of pseudoaneurysm include infection, trauma, autoimmune diseases, and medical factors. Most of the APs reported in western countries are traumatic and medical in origin, and the proportion of traumatic and medical pseudoaneurysms reported in China is increasing year by year. 1, traumatic and medical origin pseudoaneurysm: trauma of car accident, sharp force injury of abdomen and waist, blunt injury, gunshot wound can involve abdominal aorta to cause AAP, usually traumatic pseudoaneurysm bleeds rapidly, patients appear shock in a short time, a considerable part of patients die in the process of out-of-hospital or referral, some patients who arrive at hospital through emergency are also in very dangerous condition, after clear diagnosis should After a clear diagnosis, surgery should be performed as soon as possible, and rapid and effective control of bleeding is the key to saving patients’ lives. With the widespread development of endovascular techniques, the number of AAPs caused by medical vascular injury has increased. In most cases, aneurysms occur during endovascular luminal treatment, where long rods from guidewires, catheters, or other interventional devices may penetrate the aortic wall causing vascular injury and subsequently cause pseudoaneurysms. In addition, pseudoaneurysms caused by aortic injury during other procedures near the abdominal aorta and iliac artery, such as urologic surgery, obstetrical and gynecological surgery, and orthopedic surgery, have also been reported. The author’s vascular surgery center once treated a huge internal iliac artery aneurysm caused by accidental injury to the internal iliac artery branch during obstetrical and gynecological reduction surgery and AAP caused by lumbar fracture fixation in spinal surgery, using spring coil embolization and overlapping stent isolation methods respectively, and the treatment was successful. 2. Autoimmune diseases: Autoimmune diseases can involve arteries in the pathogenesis and cause aneurysms. Giant cell arteritis can cause inflammatory necrosis of the vessel wall, resulting in aneurysmal degeneration; leukoaraiosis, which occurs in Mongolian populations, invades the connective tissue system and causes destruction of the skin, digestive tract mucosa, and arterial wall tissue, and approximately 15.8% to 27.7% of patients have vascular involvement, mainly manifesting as arterial wall Structural destruction, aneurysm formation and penetrating ulcers. A very high percentage of our AP is due to leukoaraiosis, which adversely affects surgical and endoluminal treatment because the lesions can involve the entire aorta and reduce the strength of the vessel wall to varying degrees. Other autoimmune diseases such as Wegener’s granulomatosis, polyarteritis nodosa, and Kawasaki disease can also present as aneurysms. 3. Infection: Infection is another important cause of AAP. Infection can lead to activation of serine proteases either directly through bacterial enzymes or indirectly through neutrophil infiltration, causing the vascular wall to progress from localized damage to a total lesion, which then leads to rupture of the vessel to form an aneurysm. The common causative agents of infectious aneurysms are Salmonella, Escherichia coli, Staphylococcus aureus and anaerobic bacteria, and fungal infections may occur in cases of immunocompromise. The route of infection in the vessel wall can be formed by infection through the trophoblastic vessels of the arterial wall during sepsis or by direct invasion of infection from adjacent organs. Second, examination methods 1. Color ultrasound Doppler examination: Among various imaging examinations, ultrasound is the most commonly used, non-invasive and cheapest examination means, often used as screening of aneurysm and follow-up of small aneurysm. CDU allows a clear diagnosis of APP and the observation and measurement of the location and size of the aneurysm rupture and the morphology of the aneurysm. Studies have shown that measurement data from different operators may have a 5
The error of 5 mm in the measurement data of different operators and the underestimation of the aneurysm neck diameter by 2~4 mm are necessary for more accurate imaging before intracavitary treatment. 2.Computed tomography angiography: This is an important examination before surgery. In addition to cross-sectional images, it can also achieve three-dimensional reconstruction of the blood vessels and display the aortic morphology in a more intuitive and multi-angle manner. CTA allows observation of the location and course of important vascular branches near the aneurysm and assessment of the relationship between adjacent organs and the aneurysm. The measurement of vascular-related data in the anchorage area before endoluminal treatment is also achieved by CTA. At present, CTA can be considered as the most important examination and evaluation method before abdominal aortic aneurysm surgery. 3.Magnetic resonance angiography: MRA can show aortic and aneurysm morphology, but it cannot reach the level of CTA in terms of spatial resolution, and is generally not used as the preferred examination method. 4.Digital subtraction angiography: With the advancement of CTA and magnetic resonance angiography, DSA is no longer used as a purely diagnostic test and is generally used only in surgery. Its advantage is that the dynamic blood flow changes of the aneurysm can be observed. If the condition is complicated, DSA can be performed preoperatively if necessary to provide assistance in developing treatment plans. 5.Immune function examination and bacteriological examination: For non-traumatic and medically induced pseudoaneurysm, routine immunological examination and bacteriological examination are required. At present, the etiology and pathogenesis of immune aneurysms are still unclear, and there are no specific laboratory indicators and examination methods for this type of aneurysm. In the case of leukoaraiosis, for example, the diagnosis is still established by combining the patient’s medical history, physical examination, family history, and other clinical information. There are also no specific diagnostic indicators for polyarteritis major, and the diagnosis is more often based on the patient’s age, gender, clinical symptoms and characteristic vascular images. However, the examination of C-reactive protein, blood sedimentation and other indexes is helpful in determining the activity of the disease, adjusting the dose of immunosuppressive drugs, and providing assistance in the selection of clinical treatment timing. In cases of suspected infected aneurysm, blood bacteriological examination should be routinely and repeatedly performed. Different literature reports the positive rate of blood culture for infected aneurysm to be 66%-100%. In patients undergoing open surgery, intraoperative pus, angioma wall, and peri-infected tissue should be routinely retained for bacterial culture. At the same time, the possibility of anaerobic bacterial infection should not be ignored, and fungal examination should be performed in cases of long-term antibiotic application or immunodeficiency. Treatment 1. Open surgical treatment: For non-infectious AAP, open surgery is an important method, and its status is still irreplaceable even today with the rapid development of endoluminal technology. Open surgery can firmly repair the diseased segment vessels, and its long-term efficacy is reliable with low re-intervention rate. Therefore, open surgery should be considered first for aneurysms that are well tolerated by surgery and whose necks can be easily controlled. During surgery, the bleeding proximal and distal arteries should first be controlled, the diseased segment vessels should be replaced, the hematoma and pseudoaneurysm aneurysm wall should be removed, and if the rupture is small, repair can be considered. However, in most cases, pseudoaneurysms with huge aneurysms, especially those near the renal artery area, cause great difficulties in revealing the proximal neck of the aneurysm, and sometimes require revealing and controlling the suprarenal abdominal aorta or even the thoracic segment aorta to complete the vascular block, which increases the risk of surgery. Pseudoaneurysms in the area of visceral artery branches can be treated by the “hybridization technique”. The “hybrid technique,” also known as “compound surgery,” involves translocating or diverting the visceral artery in the area of the aneurysm through open surgery, and then isolating the aneurysm with an overmolded stent. The “hybrid technique” reduces the surgical risk of completely open thoracoabdominal aortic aneurysms and allows for the treatment of patients with poor surgical tolerance and advanced age. In addition, in cases of immune aneurysms, the condition of the autologous vessels at the anastomosis site should be observed during surgical treatment. In some patients, the strength of the vessel wall is extremely poor, causing difficulties for the anastomosis. Attention should be paid to the preparation of suture reinforcement materials, and even the need to raise the position of the anastomosis to avoid the extremely poor area of the vessel wall, and the formation of pseudoaneurysm with re-rupture of the proximal anastomosis after surgery is also a common problem. 2.Endoluminal treatment: Non-infected pseudoaneurysms are now mostly treated endoluminally, especially traumatic and medically induced pseudoaneurysms. The strength of the vessel wall in the anchorage area is good, and the perioperative mortality and complication rates of endoluminal treatment are significantly lower than those of open surgical procedures. Endoluminal treatment can avoid the huge trauma of open surgery, which is undoubtedly beneficial to patients. Endoluminal treatment can quickly and effectively control active bleeding, which is helpful to improve the success rate of resuscitation, and endoluminal stent implantation can also be chosen to control bleeding before surgical treatment for ruptured infected aneurysm, as a bridging procedure to second-stage open debulking surgery. There are many approaches that can be taken in APP endoluminal repair, and the most common method is endoluminal repair using an overlapping stent graft, which can quickly and effectively cover the ruptured aorta, seal the rupture, and restore the integrity of the aorta. In cases where the rupture is located in the middle segment of the abdominal aorta, there are good anchorage zones in the distal and proximal parts of the abdominal aorta, which can be repaired using straight overlapping stents; in the rupture of the lower segment of the abdominal aorta, it is usually necessary to use a bifurcated stent graft with the distal anchorage zone placed in the iliac artery; the rupture of the upper segment of the abdominal aorta is more difficult to deal with, especially in cases of immune vascular disease, where the strength of the vessels is poor and a certain area around the rupture is The vessel wall is even worse, therefore, anchoring away from the rupture is required. The upper segment of the rupture often needs to cover the renal artery or even the mesenteric artery to have a satisfactory anchoring distance. At this time, branch artery revascularization is needed, and in the past, hybridization surgery was mostly used to reconstruct the visceral artery with good results; however, assisted open surgery is required, which is still relatively traumatic and has a high surgical mortality rate; at present, the technique of intracavitary reconstruction of the visceral artery is becoming mature, and there are chimney technique, open window technique, branch stent technique, sandwich technique and other methods available. The chimney technique has a higher incidence of internal fistula, and should be chosen with caution in pseudoaneurysms especially when there is active bleeding. The open-window technique to reconstruct the blood supply to the visceral artery is a better choice and can effectively extend the proximal anchorage zone with a lower incidence of endovascular fistula. Customized open-window stent grafts are generally difficult to apply to pseudoaneurysms due to the long waiting time, and the on-stage open-window method can be used when necessary, but the technique is difficult and requires experienced units to perform. Sandwich or octopus technique is not applicable in endoluminal surgery for pseudoaneurysms because the aortic lumen of pseudoaneurysms is generally not dilated and does not have as wide a space as a true aneurysm to pass multiple stent vessel grafts; therefore, this technical method should be chosen with caution. In some special cases, such as small ruptures, ruptures near important visceral branches, and patients in poor condition who cannot tolerate complex surgery, the multilayer bare stent technique, blocker technique, spring-ring embolization technique, or a combination of several methods can be used to achieve hemostasis. The use of these methods relies on careful preoperative evaluation, which includes the morphology of the tumor, the size and location of the breach, the relative position of the vessels in the visceral area to the breach, and the experience of the operator is also a factor that must be considered. Regarding the application of these methods, only a few case reports or case reports have been seen, and their near and long-term efficacy still needs to be summarized and studied in more cases, and the super-indication application should be carefully selected. 3, treatment of infected pseudoaneurysm: The incidence of infected aortic aneurysm is low, and MAA accounts for about 0.65%-2% of all aortic aneurysms in Europe and the United States, and no relevant statistics are available in China. Infected aneurysms are aggressive and have a high mortality rate, with 44% mortality associated with aneurysm rupture and sepsis reported in the literature [4], and their treatment is challenging, and the choice of treatment method is still more controversial. The rational use of antibiotics is the basis for the treatment of infected aneurysms. The use of broad-spectrum antibiotics should be started as early as possible in clinical cases suspected to be infected aneurysms, without waiting for the results of bacterial culture and drug sensitivity tests. The drug of choice should be a broad-spectrum antibiotic that is effective against Gram-negative bacilli, positive cocci, and anaerobic bacteria, with a switch to targeted antibiotics after the results of the drug sensitivity test are available. Some patients with small tumors and stable status can be treated with antibiotics for 2~4 weeks first.
This can increase the perioperative safety. The time frame for antibiotic use is more controversial, with the literature reporting periods ranging from 4 weeks to lifelong dosing. The author believes that the time frame for antibiotic administration should be individualized to develop a protocol. Factors to consider include the type of bacteria, the extent of lesion clearance during surgery, the patient’s systemic status, the presence of immune dysfunctional disease, and the need for subsequent immunosuppressive drugs. Bacterial cultures and abdominal CT should be repeated several times before discontinuing the drug to observe the control of periaortic infection, the clinical presence of fever, elevated white blood cells and neutrophils, and the return of normal blood sedimentation and C-reactive protein. Antibiotics should be administered for as long as possible when the situation is uncertain. Open surgery and endoluminal surgery for infected aneurysms are more controversial. It is difficult to avoid infection of the artificial material by implanting an artificial vessel in the infected area, and although bleeding can be controlled in the near term, secondary infection in the distant future is still difficult to avoid completely. The preferred treatment is generally considered to be local debridement and dissection of the external bypass to restore blood supply to the lower extremity. The patency rate after axillary-bifemoral bypass is low, and there is still a high rate of amputation in the long term. Most of the postoperative patient deaths are due to re-rupture of the closed stump of the aorta or complications from systemic infection. With the development of highly potent antibiotics, the control of clinically serious infections has been significantly improved, and some experts at home and abroad advocate in situ aortic reconstruction, and the literature reports better postoperative outcomes. Xiao Zhanxiang [5] reported the treatment of infected abdominal aortic aneurysm by using a relatively clean area of retroperitoneum with primary-bilateral external iliac artery bypass, closing the end of abdominal aorta and common iliac artery, followed by incision and drainage of the aneurysm and filling the aneurysm cavity with tipped large omentum, and four patients survived in good health with satisfactory results at 5 years of follow-up, and this method deserves attention and further study. Endoluminal repair surgery is another option for infected aneurysms.In 2014, Sorelius et al [6] in Cardiovascular
Surgery published data on the largest group of cases of infected abdominal aortic aneurysms treated with endoluminal therapy to date. The study was a multicenter retrospective study involving 16 European vascular surgery centers that enrolled 130 infected aneurysms in 123 patients, all of whom were treated with endoluminal isolation techniques. Of these, 78 were abdominal aortic aneurysms with a mean follow-up of 35 months and survival rates of 75%, 55% and 41% at 1, 5 and 10 years, respectively. The study concluded that the endovascular luminal technique is feasible for the treatment of abdominal aortic aneurysms, with long-term survival and complication rates within acceptable limits, and that postoperative deaths are mainly infectious events, with long-term antimicrobial agents and lifelong follow-up recommended. Our opinion is that the endoluminal technique greatly reduces the trauma and risk of open surgery, but does not address the removal of infected lesions, which is the main reason for the poor long-term prognosis of uncontrolled infection. Endoluminal treatment of infected aneurysms should be selective. Endoluminal repair treatment can be chosen for cases where the infection is limited and can be drained by puncture or small incision, while endoluminal treatment alone is not appropriate for extensive peripheral tissue infection, especially if it invades the spine, gastrointestinal tract or even forms a gastrointestinal fistula or vena cava fistula. In case of poor general status or acute blood loss, endoluminal repair can first stop the bleeding and gain time for subsequent open surgery. In conclusion, AP is more difficult to treat, has higher mortality and complication rates than true aneurysms, and treatment options need to be carefully considered, both individually tailored and in relation to the physician’s technical condition. Infected aneurysms require even more individualized selection of treatment options according to principles to avoid catastrophic consequences. For AAP, surgical treatment remains an option and is the basic treatment; endoluminal treatment, with the advantages of less trauma and low perioperative mortality and complication rates, is currently the main treatment modality with reliable results and rapid progress. However, careful treatment planning is needed to avoid complications arising from some special unfavorable factors of pseudoaneurysm, and reasonable selection of indications is the basis of successful treatment, and reducing the incidence of long-term complications is a key issue for the future development of intracavitary therapy for AP.