An 87-year-old male, presenting with generalized malaise and weight loss of 10 kg over two months, was admitted to our hospital for further examination about his clinical conditions and improving his nutritional status. The patient had diabetes mellitus (DM) and hypertension. His DM condition was well controlled that the latest HbA1c value was 5.5%. On admission, he had a blood pressure of 146/84 mmHg and a pulse rate of 74 bpm. His body temperature was 36.0℃, and peripheral pulse was normally palpable. No abnormal findings were observed on physical examination. Abdominal computed tomography (CT) scan showed chronic pancreatitis. Laboratory studies demonstrated several inflammatory findings, such as C-reactive protein (CRP) of 9.3 mg/dL and white blood cell (WBC) of 9,480 /mm3. Eleven days after admission, the patient remained asymptomatic, but he had a decreased hemoglobin of 8.1 g/dL, elevated CRP of 14.1 mg/dL, and elevated WBC of 14,100 /mm3. Chest CT was performed to rule out aspiration pneumonia, and happened to reveal mediastinal emphysema. The wall structure of the esophagus was clearly maintained, and there seemed no involvement between esophagus and mediastinal emphysema (Fig. 1a, b Arrows). The thoracic aorta exhibited some atheromatous changes, but no aneurysmal formation was observed (Fig. 1c). After collecting two blood culture specimens, empirical intravenous antibiotics (Cefpirome 2 g/day) were administered. The patient responded favorably, and he regained his appetite on day 14. His laboratory results were also improved (CRP 5.7 mg/dL, WBC 7,340 /mm3). Thereafter, he fully recovered, and antibiotics administration was stopped on day 22.

a, b A chest computed tomography (CT) showing mediastinal emphysema (Arrows). c The thoracic aorta exhibited some atheromatous changes but no aneurysmal formation. d, e A contrast-enhanced chest CT showed peri-aortic emphysema (Arrows). f Three-dimensional CT angiography demonstrated marked pseudo aneurysmal formation around the aortic arch

On admission day 25, the patient complained of severe chest pain. He developed sudden respiratory failure and shock. Laboratory studies showed several inflammatory findings, such as CRP of 9.3 mg/dL and WBC of 9,480 /mm3. D-dimer was measured 3.6 µg/mL. Bed side transthoracic echocardiography showed no remarkable findings of wall motion abnormality and valvular disfunction. Contrast-enhanced chest CT showed peri-aortic emphysema (Fig. 1d, e Arrows) Moreover, three-dimensional CT angiography demonstrated aortic rupture and marked pseudo aneurysmal formation around the aortic arch (Fig. 1f). The patient was referred to the unit of cardiovascular surgery in other hospital. Emergency surgery was performed, and showed ruptured aortic arch and pseudo aneurysm was filled with hematoma. Abscess formation was also found around the aneurysm. After removing infectious lesions, total arch replacement was performed. Klebsiella pneumoniae was detected in both sputum and blood cultures. The species was susceptible to cephem antibiotic. Based on this, the appropriate antibiotics were administered post operative days. The patient had an uneventful hospital course and was eventually discharged.

An 82-year-old male who had comorbidities of hypertension and dyslipidemia was admitted to our hospital for general malaise and anorexia. About 15 years ago, the patient underwent Y-graft replacement in the abdominal aorta for an abdominal aortic aneurysm. On admission, he had a blood pressure of 132/76 mmHg and a pulse rate of 80 bpm. The body temperature was 36.7℃, and laboratory data showed several inflammatory findings, such as CRP of 3.9 mg/dL and WBC of 8,320 /mm3, and deteriorated renal function (Cre 2.91 mg/dL, eGFR 17.1 mL/min/1.73m2). Abdominal CT on admission day 6 revealed emphysematous changes, adjacent to the abdominal aorta (Fig. 2a Arrow), but the patient reported no abdominal symptoms. During this time, the focus of the inflammatory findings was not identified. However, the empirical intravenous antibiotics (Ceftriaxone 2 g/day) were still administered until the discharge. The patient gradually recovered, and the laboratory results normalized. The patient was discharged 19 days after admission.

a An abdominal CT showed emphysematous changes adjacent to the abdominal aorta (Arrow). b, c Plain CT images on re-admission (asterisk; stomach, Arrowhead; duodenum, Arrow; emphysematous changes). No remarkable change compared to the CT findings of Day 6. d, e An abdominal CT revealed an enlarged stomach (Fig. d Asterisk) and duodenum (Fig. e Arrowhead), filled with high-density massive contents proximal to the area adjacent to the abdominal aorta

Four days after his discharge, he returned to our emergency room for epigastric pain, occurring in the morning. Abdominal CT showed no remarkable change compared with the findings 18 days earlier. The emphysematous changes adjacent to the abdominal aorta was also detected (Fig. 2b, c Arrow). He was admitted again, but he went into a state of shock 5 h after admission. The patient eventually went into cardiopulmonary arrest immediately after an episode of hematemesis. Abdominal CT revealed an enlarged stomach and duodenum, filled with high-density massive contents, proximal to the area adjacent to the abdominal aorta (Fig. 2d Asterisk, E Arrowhead). He died of hemorrhagic shock despite cardiopulmonary resuscitation.