A rare case of ruptured infrarenal aortic aneurysm infected with Haemophilus influenzae type B

CASE PRESENTATION A 56-year old woman presented to the emergency department with a vague history of abdominal pain that had persisted for five days. A long-standing smoker, she was otherwise healthy with no previously diagnosed chronic medical conditions, and had no recent exposure to any sick contacts; she did admit to having a short episode of an upper respiratory tract infection two weeks previously that self-resolved. There was also no recent history of travel. On examination, she was tachycardic (110 beats/min to 115 beats/min), hypertensive (169/110 mmHg) and afebrile, and had a soft but tender abdomen. White blood cell count was in the 20×109/L range. Computed tomography (CT) angiography of the abdomen and pelvis revealed a 4 cm infrarenal aortic aneurysm extending to the aortic bifurcation with an associated 6.4 cm × 10 cm periaortic hematoma suggestive of rupture (Figure 1). The renal arteries and visceral vessels displayed mild atheromatous changes; other intra-abdominal structures were unremarkable. The patient’s relatively young age and female sex, coupled with the relatively small size and inflammatory appearance of the ruptured aneurysm on CT scan, were highly suggestive of a mycotic aneurysm. Blood cultures were drawn and ciprofloxacin and cefazolin were initiated. The patient was brought to the operating room for emergent open repair through a midline transperitoneal approach. Intraoperatively, note was made of an edematous retroperitoneum and an adherent duodenum. There were significant inflammatory changes in the aorta, extending distally into the iliac arteries. The periaortic fluid was noted to be nonpurulent; a sample of this was sent for Gram stain, and was reported as “moderate polymorphs with no organisms seen”. Given these nonspecific findings, the aneurysm was repaired with an in situ aorto-bi-iliac 12 mm × 7 mm Hemashield graft. The patient was then transferred to the intensive care unit (ICU) for postoperative care and continued on ciprofloxacin and cefazolin. Recovery was complicated, however, with acute occlusion of the graft. The patient underwent a second surgery with extensive thrombectomy of both limbs of the graft, as well as a left iliofemoral bypass due to consistently poor flow. The patient continued to decline, requiring increasing pressors to maintain hemodynamics. Antibiotics were broadened to include meropenem, vancomycin and fluconazole to treat her sepsis, despite negative blood cultures drawn at the time of the initial presentation. Additional complications included the need for hemodialysis for renal failure.