Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3723_Библиотеки_им_академика_М_И_Перельмана

generally less susceptible to infection due to their microcirculation. Dacron grafts were found in in­vitro studies to be more likely to harbor bacteria that can adhere to its surface and are therefore coated with collagen and antibiotics to prevent infections [1, 8]. In-vivo studies have not found actual differences in prevalence of VGI among the different graft materials [9].

Early VGI occur within the rst 4months after surgery, involve virulent organisms introduced at the time of surgery (such as S. aureus), and are usually easier to diagnose since the signs and symptoms of infection and inammation are more apparent. The patient may present with sys­temic signs of infection as well as local signs of infection, including erythema and tenderness of the skin overlying the graft, sinus tract drainage, abscess, and limb ischemia. Late VGI occur after 4months, are usually indolent, and can present with no evidence of systemic sepsis [1]. Intra­cavitary VGI may have no obvious physical nd­ings. Intra-abdominal VGI may present with abdominal pain and signs of sepsis. Aortic grafts can erode into the third or fourth portion of the duodenum, resulting in intermittent, polymi­crobial bacteremia of fecal ora or occasionally gastrointestinal tract bleeding (Fig. 15.1). Intra­thoracic VGI that involves the aortic root can present with signs and symptoms similar to those of infective endocarditis, including fever, chills, heart failure, and disruption of the anastomotic suture line of the aortic root, which can result in sudden massive hemorrhage. Septic emboli can occur in the central nervous system or peripher­ally [4]. While all vascular graft infections are associated with high morbidity and mortality, those involving the thoracic aorta are the most catastrophic, with reported mortality rates rang­ing from 25% to 75% [10] (Fig.15.2).

Imaging is essential in diagnosing VGI and its accompanying complications, including discon­tinuation of its structural integrity, perigraft gas or uid collections, anastomotic leak, pseudoan­eurysms, and graft-enteric erosion or stula. Imaging also contributes to guiding perigraft uid aspiration and to optimal surgical treatment planning [7]. The MAGIC classication includes major and minor radiological criteria. Major cri­teria for the diagnosis of VGI are considered to be perigraft uid more than 3months after inser­tion, perigraft gas more than 7weeks after inser­tion, and increase in perigraft gas volume in serial imaging tests. Minor radiological criteria include suspicious perigraft gas/uid, aneurysm expan­sion, pseudoaneurysm formation and signs of infection spreading to adjacent structures such as focal bowel wall thickening and discitis/osteo-

myelitis [5]. Imaging methods include radiologi­cal and nuclear medicine modalities.

moderate [9]. Reinders-Folmer’s meta-analyses published in 2018 showed an overall pooled sen­sitivity of 67% and specicity of 63% for detect­ing VGI.In addition, the authors demonstrated that isolated CTA usually does not provide enough information for establishing the diagno­sis of VGI [11]. CTA has higher false-negative rates and a sensitivity of only 55.5% in low-grade or early VGI, as the ndings are difcult to dif­ferentiate from postoperative changes. It is more accurate, with a sensitivity and specicity of about 85–94%, in late VGI or infections accom­panied by complications such as abscesses in adjacent structures or stula. Radiological fol­low- up with serial CTA can increase diagnostic accuracy by showing persistent or worsening ndings. Like US, CT can be used for guided aspiration of perigraft uid [7].

monly used in recent years due to preferable physical characteristics and less radiation expo­sure to the patient. The labeled granulocytes migrate to the infection site and accumulate there over time [7]. The European Society of Nuclear Medicine (EANM) guidelines published in 2018 recommend several (at least dual) time point image acquisitions of the investigated regions, with times corrected for isotope decay. Early post injection images (30min to 1h) and delayed images (2–4h) may be sufcient for the diagnosis of VGI, but the addition of late images (20–24h) is strongly recommended in equivocal cases, low grade or chronic infections, and in follow-up studies. The use of single-photon emission computed tomography (SPECT/CT) increases the diagnostic accuracy and helps in evaluating the infection’s extent and location [11, 12]. Interpretation is derived by comparing the uptake intensity in the suspected site of infection between the early and late images. Infection is characterized by increased intensity of uptake over time, while in a sterile inamma­tion site the labeled WBC uptake will decrease or be stable over time. A study by Puges etal. published in 2019 found WBC scintigraphy as the most accurate method of diagnosing VGI, with sensitivity and specicity of 89.5% and