動脈瘤の定義は，「正常血管の150％以上に拡張したもの」だから，図１の大動脈径は約1.5cmで，図３の↑病変は3cm以上あり，大動脈内腔外の造影剤を含み（△）大動脈瘤である．大動脈は直線的に下行しているから瘤は左側に突出し嚢状を呈し，ガス（▲）を含む．臨床的に熱があること，嚢状であることと，ガスを含むので感染性動脈瘤と診断する．血管造影で動脈瘤（図A：白矢印）が確認され手術となった．動脈瘤と膿瘍を摘出し，in situ（解剖学的経路）人工血管置換術を施行し，順調に経過している．膿からはsalmonella entericaが検出された．

参考症例（感染性腹部大動脈瘤）：脳出血後寝たきりの76歳男性．第3，第4胸椎の化膿性脊椎炎のため両下肢麻痺，胸部以下の痛覚消失が出現し，血液培養で黄色ブドウ球菌が検出された．図１〜図５はその時の腹部CT．12日後，抗生物質投与にもかかわらず発熱が続き，腹部に拍動性の腫瘤が触知されたので再度腹部のCT検査を行った．
12日前のCT（図１〜図５）では大動脈（A）瘤や周囲に異常所見を認めない．図８〜図１１の▲は動脈瘤で，図７〜図１２の↑は動脈瘤周囲の血腫，すなわち腹部大動脈瘤破裂と診断され手術となったが，膿瘍（↑）を伴う感染性動脈瘤と判明した．膿培養からはstaphylococcus aureus とbacteroides fragilis が検出された．発熱が続いている，急に発生した動脈瘤，大動脈（A）はまっすぐ下降し，動脈瘤（▲）は左側へ突出しているから嚢状動脈瘤であることを考え合わせると，感染性動脈瘤を疑うべきであった．

文献考察１）：感染性動脈瘤（infected（mycotic）Aortic Aneurysm）．死亡率は5%（infrarenal：0%），起因菌はSalmonella属が最も多く74％，次いでStreptococcus species が11%．in situ 置換が有効である．
J Vasc Surg. 2002 Oct;36(4):746-50.
Surgical treatment for primary infected aneurysm of the descending thoracic aorta, abdominal aorta, and iliac arteries.
Hsu RB, Tsay YG, Wang SS, Chu SH.

OBJECTIVE AND METHOD: In this retrospective review, we report the surgical results of infected aortic aneurysms treated at a single center over 5 years. RESULTS: From October 1996 to October 2001, 19 patients with infected aortic aneurysm were treated with surgery, nine with suprarenal infections (four proximal descending thoracic aortic aneurysms, two distal descending thoracic aortic aneurysms, and three suprarenal abdominal aortic aneurysms) and 10 with infrarenal infections (eight infrarenal abdominal aortic aneurysms and two iliac artery aneurysms). All had a positive blood or tissue culture; 89% were febrile, 89% had leukocytosis, and 32% were hemodynamically unstable. The most common responsible pathogens were Salmonella organisms (74%) followed by Streptococcus species (11%). Nine of 10 infrarenal infections were caused by Salmonella organisms. Both infrarenal and suprarenal infections were treated with wide debridement of infected aorta, in situ prosthetic graft or patch repair, and prolonged intravenous antibiotics. Hospital survival rate was 95%: 100% for infrarenal and 89% for suprarenal infections. There was no perioperative intestinal ischemia or perioperative limb loss. Acute renal failure occurred in two patients with suprarenal infection. Late deaths have occurred in three patients with one early graft infection (5%) resulting in the only one in-hospital death at 4 months. Sixteen patients remain alive at mean follow-up of 17.8 months (range, 4-47 months). There have been no late aortic or graft infections. During the same period, there were five unoperated patients, four of whom died of shock during hospitalization. CONCLUSIONS: Infected aortic aneurysm is common in Taiwan, and Salmonella species were the most common responsible microorganisms. With surgical intervention and prolonged intravenous antibiotics, in situ graft replacement provided a good outcome. The incidence of prosthetic graft infection was low, even in patients with infections due to Salmonella species and with in situ graft replacement.PMID: 12368720

文献考察２）：全大動脈瘤の0.7%，53％が破裂例，死亡率は21%，in situ置換が有効．
J Vasc Surg. 2001 Nov;34(5):900-8.
Infected aortic aneurysms: aggressive presentation, complicated early outcome, but durable results.
Oderich GS, Panneton JM, Bower TC, Cherry KJ Jr, Rowland CM, Noel AA, Hallett JW Jr, Gloviczki P.

OBJECTIVE: Infected aortic aneurysms are rare, difficult to treat, and associated with significant morbidity. The purpose of this study was to review the management and results of patients with infected aortic aneurysms and identify clinical variables associated with poor outcome. METHODS: The clinical data and early and late outcomes of 43 patients treated for infected aortic aneurysms during a 25-year period (1976-2000) were reviewed. Variables were correlated with risk of aneurysm-related death and vascular complications, defined as organ or limb ischemia, graft infection or occlusion, and anastomotic or recurrent aneurysm. RESULTS: Infected aneurysms were infrarenal in only 40% of cases. Seventy percent of patients were immunocompromised hosts. Ninety-three percent had symptoms, and 53% had ruptured aneurysms. Surgical treatment was in situ aortic grafting (35) and extra-anatomic bypass (6). Operative mortality was 21% (9/42). Early vascular complications included ischemic colitis (3), anastomotic disruption (1), peripheral embolism (1), paraplegia (1), and monoparesis (1). Late vascular complications included graft infection (2), recurrent aneurysm (2), limb ischemia (1), and limb occlusion (1). Mean follow-up was 4.3 years. Cumulative survival rates at 1 year and 5 years were 82% and 50%, respectively, significantly lower than survival rates for the general population (96% and 81%) and for the noninfected aortic aneurysm cohort (91% and 69%) at same intervals. Rate of survival free of late graft-related complications was 90% at 1 year and 5 years, similar to that reported for patients who had repair of noninfected abdominal aortic aneurysms (97% and 92%). Variables associated with increased risk of aneurysm-related death included extensive periaortic infection, female sex, Staphylococcus aureus infection, aneurysm rupture, and suprarenal aneurysm location (P <.05 for risk of vascular complications extensive periaortic infection female sex leukocytosis and hemodynamic instability were positively associated conclusion: infected aortic aneurysms have an aggressive presentation a complicated early outcome. however late outcome is surprisingly favorable with no aneurysm-related deaths low graft-related complication rate similar to standard aneurysm repair. in situ grafting safe durable option most patients.pmid:>