Clostridium septicum: a usual suspect? Aortic rupture following right hemicolectomy.

Abstract

BACKGROUND Mycotic Aneurysm (MA) is a rare, severe variant of aortic aneurysm accounting for 0.7%-3.3% of all aortic aneurysms, proving fatal in all cases without treatment. Diagnosis can prove difficult, with the mainstay being CT imaging, as clinical signs and symptoms are often vague or not present. There is a known association between Clostridium Speticum, mycotic aneurysm and colonic malognancy. We report the case of a a lethal mycotic aneurysm, identified 7 days after a right hemicolectomy for perforated caecal adenocarcinoma.

CASE REPORT A 90 year old female was admitted for lower abdominal pain. CT scan on admission demonstrated a thick walled caecum and pericaecal inflammation suspicious for a perforated carcinoma. This was confirmed at subsequent colonoscopy. Biopsy demonstrated a poorly differentiated adenocarcinoma. A laparoscopic right hemicolectomy was completed the following week after perioperative workup and intravenous antibiotic therapy. On the 9th postoperative day fever and rising inflammatory markers prompted repeat abdominal CT scan which demonstrated a mycotic aneurysm of the upper abdominal aorta. No organism was isolated on blood culture. The aneurysm was not stentable due to anatomic location across major visceral arteries, and major surgery for open repair deemed inappropriate. The decision was made to palliate, and the patient died at home from presumed spontaneous rupture two weeks after discharge.

DISCUSSION The aetiology of mycotic aneurysm involves primarily bacterial seeding, either into a previous defect in the intimal wall or via septic emboli in the vasa vasorum. Contiguous spread of infection or direct inoculation via trauma such penetrating injury have also been documented but are rare . Causative organisms include staphlyococcus, salmonella and some streptococcus species (A to C). Clostridium Septicum is causative rarely, occurring almost exclusively in association with colonic malignancy. A review article by Alimi et al in 2017 reported 51 cases of clostridium septicum aortitis. In 71% of cases colonic malignancy or premalignant lesions were found. In the case of our patient no organism was ever isolated, blood cultures remained naegative and an autopsy was not performed, precluding organism isolation from the tissue.

CONCLUSION Mycotic Aneurysm is a rare and often lethal complication, closely associated with colonic malignancy. Clostridium Septicum is the causative organism in over 70% of patients with concomitant gastrointestinal malignancy.