Mycotic aneurysm with aortoduodenal fistula

Abstract

Firstly described in the 19th century by Sir William Osler, the mycotic aneurysm (MA) is a rare entity characterized by an abnormal arterial dilation, which is potentially fatal, and is associated with the infection of the vascular wall. Elderly patients are mostly involved, especially when risk factors like chronic diseases, immunosuppression, neoplasia, and arterial manipulation are associated. The authors report the case of a young male patient diagnosed with an aortic aneurysm of infectious origin in the presence of repeated negative blood cultures. The diagnostic hypothesis was raised when the patient was hospitalized for an inguinal hernia surgery. The diagnosis was confirmed based on imaging findings consistent with mycotic aneurism. The patient was treated with an endovascular prosthesis associated with a long-lasting antibiotic therapy. Five months later, the patient attended the emergency unit presenting an upper digestive hemorrhage and shock, from which he died. The autopsy revealed a huge aneurysm of the abdominal aorta with an aortoduodenal fistula. The histological examination of the arterial wall revealed a marked inflammatory process, extensive destruction of the arterial wall, and the presence of Gram-positive bacteria. This case highlights the atypical presentation of a MA associated with an aortoduodenal fistula. Besides the early age of the patient, no primary arterial disease could be found, and no source of infection was detected.

Keywords: Aneurysm, Infected; Aortic Aneurysm; Fistula.

Figure 1. Aortic angiogram CT revealed an infrarenal aortic saccular aneurysm measuring 6.7 × 5.2 cm (arrow).

Figure 2. Abdominal CT. A (sagittal plane) - Infrarenal aortic saccular aneurysm presenting irregular contours, ulceration, surrounded by irregular dense tissue (arrow); B (axial plane) - The anterior displacement of the duodenum (arrow).

Figure 3. Abdominal CT prior to death. A - (axial plane) Gaseous focus within the endoprosthesis (arrow) indicating aortoenteric fistula; B - (sagittal plane) The presence of thrombi throughout the aortoiliac endoprosthesis (arrow).

Figure 4. Macroscopic view. A - Segment of abdominal aorta with an aneurysm of 7.0 × 5.0 cm with the lumen filled in by an aortoiliac prosthesis. Note extensive mural thrombosis; B - Third duodenal portion in close relation to the abdominal aneurysm presenting an aorto-enteric fistula covered by blood clots.

Figure 5. A - Panoramic view of the aorta with the fistula track showing the destruction of arterial wall (H&E 0.45X); B - Periaortic soft tissues infiltrated by inflammatory cells presenting suppurative areas and the fistulous track with hemorrhagic evidence remaining in its light (H&E 9.84X); C - Photomicrography of the aorta showing a segment of the aorta close to the perforation area without pathological alterations (H&E 3.29X); D - Verhoeff staining showing the area of destruction of the aorta wall, which was replaced with fibrosis (Verhoeff 1.61X).

Figure 6. A & B - Photomicrographs of the aneurysm wall showing pleomorphic Gram-positive bacilli (Brown-Hopps, 1000X).