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Paper text:
an infected thoracic aortic aneurysm ( itaa ) is a relatively rare disease , and its incidence has been reported to comprise about 1% of all aneurysms .
patients with itaa have a high incidence of aneurismal rupture due to the abrupt growth of the aneurysm .
therefore , itaa is associated with both high morbidity and mortality , and the mortality has been reported to range from 23 to 37% . regrettably , there are no standard guidelines for the medical or surgical treatment of itaa because it is a rare and frequently lethal disease .
the major concerns regarding surgical treatment of itaa are the control of infection , resection of the entire infected tissue , grafting via an aseptic route , and prevention of recurrent infection .
surgical intervention is principally indicated to prevent aneurysm rupture , and is only recommended when the maximum diameter of the aneurysm is over 55 mm or when rapid expansion of the aneurysm is observed . ideally , surgery is performed only in patients with a controlled infection , and for such patients in - situ reconstruction is also ideal .
however , emergency surgery is often required in patients with uncontrolled infection , due to the risk of aneurysmal rupture . in such cases , extra - anatomical bypass is useful for avoiding routing in the infected site and is better than using cardiopulmonary bypass , because cardiopulmonary bypass may reduce the immunologic competence following surgery .
infected aortic aneurysms have historically been classified into the following four types ; mycotic aneurysms , microbial arteritis with aneurysm , infected preexisting aneurysms , and post - traumatic infected false aneurysms .
mycotic aneurysms develop when septic emboli of cardiac origin lodge in the lumen or the vasa vasorum of the aorta .
mycotic aneurysms can occur in both normal and abnormal arteries and develop in virtually any named artery .
diseases of the intima with atherosclerosis allow blood - borne bacteria to inoculate the aortic wall . when an infection is established , suppurations , localized perforation and false aneurysm formation occur .
the predominant microorganisms involved in microbial arteritis are escherichia coli , and salmonella and staphylococcus species .
the abdominal aorta is the predominant site , and the most prevalent organisms are staphylococcus species.post-traumatic infected false aneurysms are the most prevalent type of infected aneurysms that develop in the peripheral arteries .
this type of infection may also occur in the thoracic aorta accompanied by endovascular stent grafting .
the clinical symptoms of itaa are fever , and chest / abdominal pain or discomfort .
infected aneurysms occur in all age groups , but the typical patient is older and has asthelosclerosis .   blood examination usually reveals leukocytosis and positive levels of blood c reactive protein , but these examinations are nonspecific .
several series of blood cultures are mandatory to confirm the causal bacterial species , however , negative blood cultures are common because that the majority of patients receive antibiotics before confirming the diagnosis of itaa .
the most frequent source of infection has not been identified ; however , gram - positive organisms such as staphylococcus aureus are predominant , in addition to salmonella species .
gram - negative organisms such as e. coli or bacteroides species are also frequently observed . 
 
the diagnosis of itaa is generally made comprehensively based on symptoms , laboratory data and ct findings .
itaa is generally suspected from results of ct findings in patients with symptoms of unknown fever and/or focal chest pain or discomfort .
a short - interval ct re - examination is also essential to confirm the correct diagnosis ( fig.1 - 3 ) . as with non - infectious aneurysmogenic processes ,
the ct scan commonly demonstrates rapid enlargement of the aneurysmal lumen and a soft tissue mass surrounding the aorta .
ct findings of itaa often reveal aortic nodularity , an irregular configuration , rupture of calcification , or air in an aortic wall .
one of the characteristics of itaa is the presence of several nodular or saccular aneurysms localized in different aortic portions , ( fig.4,5 ) .
indeed , infected aneurysms commonly develop as a result of bacteria invation into the aortic vessel wall ( microbial arteritis with aneurysm ) .
the presence of multiple aneurysms demonstrating either a saccular or nodular type , with a rapid expansion in size , are the most typical ct findings for itaa .
the utility of intravenous digital subtraction angiography ( dsa ) in the aorta and femoral artery has been established .
however , multi - detector computed tomography ( mdct ) is a more useful method for detecting the shapes and other aspects of aneurysms , ( fig.4,5 ) .
magnetic resonance imaging may also prove helpful when screening certain anatomic sites or when contrast media is contraindicated .
gallium scintigraphy has usually been used , but positron emission tomography ( pet ) can diagnose the precise site of inflammation . the following suv ( standardized uptake value ) is important for deciding positive findings .  
suv = uptake ( kbq / ml ) / injected dose ( kbq ) / patient weight ( g ) 
  infected aortic aneurysm occurred in thoracic aorta in 32% of cases , upper abdominal aorta in 26% of cases and lower abdominal aorta in 42% of cases , however , multiple aneurysms were detected in many cases . 
 
distal arch aorta revealed an ulcer - like protrusion with low density mass under thickened and enhanced adventitia at first ( fig.1 ) .
the ulcer - like protrusion expanded abruptly ( fig.2 ) , and the diameter of the aneurysm increased from 40 mm to 70 mm within 10 days ( fig.3 ) .
the aneurysm developed as a result of invasion of bacteria into the aortic vessel wall ( microbial arteritis with aneurysm ) .
this aneurysm expanded from 30 mm to 40 mm in diameter within the same period ( fig.5 ) .
patients with itaa have a high incidence of aneurysm rupture due to rapid growth of the aneurysm .
antibiotic therapy , using agents which are sensitive and effective against the specific causal bacterial species , is mandatory for treating the infection .
ampicillin or cepharosporin , which combat salmonella species , should be the first choice antibiotics .
bactericidal antibiotics must be given both before and after surgery , with continuous administration ranging from 4 to 8 weeks .
elective surgery is ideal for patients demonstrating a controlled infectious state . however , emergency surgery is often unavoidable due to the risk of aneurysmal rupture .
it is still difficult to determine the optimal timing of surgical intervention and the best surgical procedure .
short - interval ct re - examinations are helpful for determining the best timing for surgical intervention .
a maximum aneurysm diameter of more than 55 mm is the principle indication for surgical intervention .
in addition , a case with an abrupt aneurismal expansion of over 10 mm / week should be indicated for urgent surgery as an impending aneurysmal rupture .
the major concerns about surgical treatment for itaa are ensuring the resection of the entire infected tissue , reconstruction of the vessels via an aseptic route , and prevention of re - infection .
the exclusion or debridement of the infected aneurysm and surrounding tissues is essential , especially during the active infection phase .
however , when such patients are complicated with pyothorax , an in - situ reconstruction should be avoided to prevent re - infection , while an extra - anatomical bypass is feasible , an in - situ reconstruction can be performed and is ideal , when the entire infected tissue can be successfully excised from the patient , and the infectious state is under sufficient antibiotic therapy control .
the use of a woven dacron graft soaked with antibiotics has been reported to prevent graft infection even during in - situ replacement .
experimental studies demonstrated prolonged antistaphylococcal activity of rifampin - bonded , gelatin - impregnated dacron grafts after implantation in the arterial circulation .
a silver - coated polyester prosthesis is also available for management of aortic infections , and favorable outcomes have been reported .
a cryopreserved homograft is known to better resist bacterial colonization and to present better mechanical properties than prosthestic grafts . however
, in - situ aortic reconstruction with a cryopreserved homograft in an infected field still carries a high mortality rate . in order to reduce the risk of infection after resection of an itaa
, the defect is often filled with the omentum , or grafts are wrapped with the omentum ( omentpexy ) .
kam and colleagues reported that endovascular aortic repair ( tevar ) could be successfully carried out in an hiv positive immunocompromised host with itaa .
however , tevar for itaa is considered to be associated with a high risk of recurrence of infection , especially when aneurysms form a fistula with the gastroinstestinal tract or respiratory tract .
stellemes and collegues performed tevar as emergency therapy despite suspected aortic infection in 6 cases and reported 1 hospital mortality .
they concluded that tevar as emergency therapy is feasible , but life - long clinical and morphological surveillance remains mandatory as recurring infection can not be entirely excluded .
endovascular stenting may be indicated for high co - morbidity patients under a controlled infection state .
the bridge use of tevar can be considered to prevent an aneurismal rupture , but open surgery should be scheduled under cautious follow - up .
the surgical strategies for itaa should be determined on a case - by - case basis and include a careful ct follow - up .
specimens obtained from the itaa usually reveal the presence of lymphocytes and neutrophils , while plasma cells invade the aortic tissue with signs of an infected aneurysm .
although itaa is a relatively rare disease , it has a high morbidity and mortality rate .
the type , duration and dose of antibiotics should be determined according to the guidelines for infected endocarditis .
the mortality of itaa is much higher than for non - infected aneurysms because the prognosis of itaa is greatly influenced by the management of infection .
therefore , antibiotic therapy is the most essential part of the treatment for itaa .  
a clinical study of axillobifemoral bypass for infected infra - renal abdominal aortic aneurysm has been reported .
it showed that early and overall mortality were 24% and 42% , respectively . a higher rate of late complications was reported , including aortic stump rupture or graft infection .
several series have reported satisfactory outcomes with in - situ reconstruction , but results varied according to the graft materials .
reconstruction with in - situ cryopreserved allograft showed superior disease - related survival - free reoperation than that treated with prostatic graft . the u.s .
cryopreserved aortic allograft registry reported a 30-day mortality rate of 13% and an overall mortality rate of 25% during a mean follow - up period of 5.3 months .
it was associated with a high complication rate , including limb amputation , hemorrhage , graft occlusion and reinfection ( 3 to 14% ) . 
 
reconstruction with an antibiotic - soaked dacron graft has also been reported with better clinical outcomes .
oderich and coworkers reported an operative mortality of 21% in 43 cases and muller and coworkers reported an overall hospital mortality of 36% in 33 cases with infected aortic aneurysm .
hsu and coworkers reported a hospital mortality of 10% in 10 patients who underwent in - situ aortic arch replacement for infected aortic arch aneurysm .
they also reported that major complication including hypoxic encephalopathy occurred in 70% patients and late prosthetic graft infection occurred in 10% of patients .
extra - anatomic reconstruction was performed in 1 patient and in - situ reconstruction was performed in 7 other patients .
there were no hospital mortalities but a patient who underwent extra - anatomic reconstruction died suddenly 2 years after surgery . even when patients can survive the perioperative period , long - term reinfection can occur clinically .
indications for life - long antibiotic therapy are not well documented , however , cautious follow - up is essential for such patients .
the survival rate has been reported to be 6776% at 2 years and 47% at 5 years due to late aortic events . 

patients with itaa are associated with a high incidence of aneurismal rupture due to the abrupt growth of the aneurysms .
the major concerns regarding surgical treatment for itaa are control of infection , resection of whole infected tissue , grafting via an aseptic route and prevention of recrudescent infection .
it is essential to excise the whole infected aneurysm and to reconstruct in - situ grafting via an aseptic route .
however , urgent surgery is often required in patients with an uncontrolled infection due to impending aneurismal rupture . in such cases ,
an extra - anatomical bypass without cardiopulmonary bypass is applicable , because cardiopulmonary bypass may reduce the immunologic competence and thereby enhance septicemia .
surgical strategies should therefore be determined on a case - by - case basis because patients may present various clinical courses .
abstractinfected thoracic aortic aneurysm ( itaa ) is a relatively rare disease . 
 the diagnosis of itaa is generally made comprehensively based on symptoms , laboratory data and ct findings . 
 several series of blood cultures are mandatory to first detect the infecting organism . 
 itaa is usually suspected as a result of the ct findings . 
 a short - interval ct re - examination is essential to confirm the correct diagnosis . 
 a ct scan commonly demonstrates a rapid enlargement of the aneurismal lumen and soft tissue mass surrounding the aorta . 
 one of the characteristics of itaa is the presence of several nodular or saccular aneurysms localized in different aortic portions . 
 patients with itaa are associated with high incidences of aneurismal rupture due to the aneurysm s abrupt growth . 
 therefore , itaas are associated with both high morbidities and mortalities . 
 the major concerns regarding surgical treatment for itaa are the control of infection , the resection of whole infected tissue , grafting via an aseptic route and the prevention of recrudescent infection . 
 therefore , effectual antibiotic therapy is mandatory as the first choice of therapy . 
 ideally surgical intervention is indicated in patients with a controlled infection . 
 it is essential to excise the whole infected aneurysm and to reconstruct in - situ grafting via an aseptic route . 
 however , urgent surgery is often required in patients with an uncontrolled infection because they have an impending aneurismal rupture . in such cases , 
 an extra - anatomical bypass without cardiopulmonary bypass is applicable . 
 surgical strategies should therefore be determined on a case - by - case basis because these patients present various clinical courses .