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Paper text:
a 48-years - old male with recent prosthetic replacement of the mitral and aortic cardiac valves three months earlier , was hospitalized with clinical and laboratory evidence of sepsis .
transthoracic echocardiography detected a vegetation consistent with infectious endocarditis of the mitral prosthesis , but the fever persisted despite intensive antibiotic therapy .
total - body , contrast - enhanced , computed tomography ( ct ) requested to investigate possible sites of infectious dissemination detected a small metastatic brain abscess and maxillary sinusopathy , excluding lung septic emboli .
incidentally , a saccular aneurysm with a 3-cm maximum diameter and minimal peripheral thrombosis was detected , originating from the distal branches of the superior mesenteric artery [ figures 1a and b ] .
axial ( a ) and sagittal ( b ) maximum intensity projection ( mip ) algorithm ct - angiographic images from initial total - body ct , show a roundish 3-cm aneurysm , originating from the distal branches of the superior mesenteric artery ( arrowheads ) .
repeat ct shows a persistent mesenteric aneurysm , with internal hyperdensity , on an unenhanced image ( c ) and absent contrast perfusion during a vascular enhanced study ( d ) .
color - doppler ultrasound ( e ) confirms spontaneous aneurysmal thrombosis , with internal echogenicity and absent flow signals .
the lesion completely disappeared on the six - month ct follow - up ( f ) after blood cultures disclosed aspergillus flavus and nocardia spp systemic infection , sepsis was successfully treated with intravenous cotrimoxazole plus antimycotic drugs .
two weeks later , a repeat ct - angiography showed a persistent mesenteric aneurysm , with unchanged size , increased basal attenuation , and absent contrast medium perfusion [ figures 1c and d ]  findings consistent with its spontaneous thrombotic occlusion .
a color - doppler ultrasound confirmed a completely thrombosed aneurysm with internal echogenicity and absent flow signals [ figure 1e ] .
six months after hospital discharge , a follow - up ct showed complete disappearance of the visceral aneurysm [ figure 1f ] .
infected ( mycotic ) aneurysms represent one of the rarest extra - cardiac complications of septic endocarditis , compared to the more frequent involvement of the central nervous system , lungs , spleen , kidneys , and musculoskeletal system .
high - risk categories include patients with cardiac valvular abnormalities or prosthetic valves , history of intravenous drug use , diabetes , and immunosuppressive conditions , such as the human immunodeficiency virus infection .
the pathogenesis of mycotic aneurysms involves a hematogenous spread of septic emboli ( most , usually due to staphylococcus aureus ) into the vasa vasorum of the aorta , peripheral , cerebral or visceral arteries .
the resulting infectious arteritis causes damage and the subsequent contained rupture of the vessel wall , leading to the formation of a saccular luminal outpouching representing a pseudoaneurysm .
mycotic lesions represent only 10% of all visceral aneurysms , most commonly caused by atherosclerosis .
the superior mesenteric artery is the most frequently involved visceral vessel , with mycotic aneurysms usually located in the distal arterial bed . often , clinically unsuspected in patients with sepsis
, mycotic aneurysms may sometimes cause abdominal pain or be appreciated as pulsatile masses . despite advanced antibiotic therapies ,
these lesions are associated with significant morbidity and a 50% mortality rate , resulting from both disseminated sepsis and a propensity to rupture , therefore , prompt detection is imperative .
currently , multidetector ct represents the preferred modality to image patients with sepsis . allowing a fast panoramic exploration of the systemic arterial bed and production of a detailed multiplanar , and three - dimensional , ct - angiographic reconstructions ,
the volumetric contrast - enhanced ct allows confident identification , characterization , and vascular anatomy mapping of arterial lesions.[135 ] the usual imaging appearance of a mycotic aneurysm includes a saccular vascular dilatation , sometimes associated with edematous changes in the surrounding tissue planes .
the arterial walls may appear indistinct and irregular , whereas , mural calcifications are exceptional compared to uninfected atherosclerotic dilatations.[14 ] sometimes incidentally detected mycotic aneurysms may require open surgery , endovascular stent placement or angiographic embolization , medical treatment or a combination of these .
small , non - ruptured aneurysms are managed with intravenous antibiotics for four to six weeks , with imaging surveillance , best performed with repeated ct studies .
alternatively , a color - doppler ultrasound allows a non - invasive follow - up , although with limited reproducibility .
as demonstrated by this case , a characteristic feature of mycotic aneurysms is their rapid development and unpredictable behavior : these lesions may undergo partial or complete thrombosis as a response to medical treatment , decrease in size or otherwise enlarge . ct - angiography detection of signs of impending or frank rupture , such as , contrast extravasation , consistent with active bleeding , indicate the need for urgent interventional or surgical treatment .
one of the rarest complications of endocarditis , infected ( mycotic ) aneurysms result from haematogenous dissemination of septic emboli and occur more frequently in patients with cardiac valvular abnormalities or prosthetic valves , intravenous drug abuse , diabetes and immunosuppression conditions such as hiv infection . although often clinically unsuspected , mycotic aneurysms are potentially life - threatening because of disseminated sepsis and propensity to rupture . 
 contrast - enhanced multidetector ct provides prompt detection , characterization and vascular mapping of these lesions , allowing correct planning of surgical or interventional therapies and reproducible follow - up . 
 because of their characteristically unpredictable behaviour , mycotic aneurysms may undergo spontaneous thrombosis , size reduction , rapid enlargement or rupture , therefore strict imaging surveillance with ct and/or color doppler ultrasound is necessary .