Mongi Slim La Marsa Hospital; Faculty of Medicine, ¹University of Sfax, Tunisia and ²University of Tunis El-Manar, Tunis, Tunisia.

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Infective endocarditis (IE) is associated with high mortality and severe complications. Infectious aneurysms, a rare complication, result from septic arterial embolism to the intra-luminal space or vasa vasorum or from subsequent spread of infection through the intimal vessels. Aneurysms of the superior mesenteric artery (SMA) and its branches are uncommon and have a high rate of rupture and mortality. We describe the presentation and management of a case of infective endocarditis and ruptured SMA branch aneurysm. 

A 50-year-old female, diagnosed with mitral insufficiency 15 years ago presented with fever associated with systemic symptoms of chills, poor appetite and weight loss. Physical examination showed a systolic murmur at mitral region. Transthoracic echocardiography showed valvular vegetation (15×10 mm) associated with mild mitral insufficiency. The patient was treated with probabilistic antibiotic therapy (oxacillin, ampicillin and gentamycin) with good initial evolution. During pre-surgery evaluation, the patient developed abdominal pain, and hemorrhagic shock. Computed tomography angiogram revealed hemoperitoneum, and contrast extravasations due to aneurysms rupture originating from an SMA’s branch  [Fig.1]. The patient was transferred for urgent surgery. On laparotomy large, inflamed, pulsatile mesenteric mass with free blood in the pelvis was found. The transverse mesocolon was retracted and proximal control of the SMA obtained at the base of the mesentery. The aneurysm was adherent to the retroperitoneum. Evidence of necrotic small bowel was detected and resection of 25 cm with ileostomy was performed [Fig.2]. The entire bowel was inspected and showed no evidence of further ischemia. On 6th postoperative day (POD), the patient was extubated and transferred out of the intensive care. Although cultures of the mesenteric aneurysm were sterile, urine culture drawn after the surgery revealed Klebsiella pneumonia BLSE (bêta-lactamases à spectre étendu). After a 49-day hospital stay, the patient was discharged and a surgery for restoring bowel continuity after ileostomy was programmed three months later with good results.

SMA aneurysms are a rare complication of infective endocarditis. In fact, the true incidence of main trunk SMA aneurysms is unknown but they are estimated to number between 5.5-8.6% of all splanchnic artery aneurysms. Side branch aneurysms are even rarer, as did our patient [1-8]. Incidence and rupture risk are as much as two-fold higher in men and 19% of patients will have synchronous aneurysmal disease at other sites [5,6]. The number of SMA aneurysms discovered incidentally, with the utilization of cross-sectional imaging, has risen from 10% to 50% in some studies [4,6,9-11]. Reported size for main SMA trunk aneurysms varies from 2 to 9 cm, with side branch aneurysms usually less than 1 cm [12,13]. Historically, infection has been the major etiology of SMA aneurysms, accounting for 31 to 63% of them [13,14]. The microorganisms mostly implicated are Streptococcal and Staphylococcal species; however blood cultures are negative in 18 to 50% of cases and failure to isolate specific microbes from excised tissue is not uncommon [6,15]. This was the case in our patient. Nevertheless, a germ was identified in his urine culture which causality can’t be assured. 

The most common symptom associated with SMA aneurysms is abdominal or back pain, with a frequency of 60 to 70% of patients [5-8,11]. Rupture risk is higher than other splanchnic aneurysms (38% to 50%). It can manifest either by intra-peritoneal hemorrhage, mesenteric hematoma, or intra-luminal rupture with gastrointestinal bleeding [5,6,8]. The correlation between aneurysm size and rupture risk has not been completely established. Conventional arteriography was used to diagnose up to 75% of SMA aneurysms. It has now been supplanted by cross-sectional imaging [5]. 

Endovascular techniques, ranging from trans-catheter embolization to stent grafting, have been used to treat SMA aneurysms, even in the setting of rupture with hemodynamic instability [1,4,6,7,9]. These techniques offer advantages by virtue of their minimally invasive nature and potential for preservation of in-line flow. However, there are obvious concerns surrounding their adoption for the management of mycotic aneurysms. In fact, when endovascular strategies were used at other anatomic sites, the rate of persistent infection was as high as 25%, and 1-year survival was as low as 39% in reported series [15]. Concomitant bowel resection has been required in more than one-third of cases in some of the larger series of SMA aneurysms, thus, attentive evaluation to rule out potential bowel ischemia is imperative before the decision of an endovascular approach [6]. Endovascular treatment for mycotic SMA and branch aneurysms, may have retain a place in patients with high operative risk and limited life expectancy. Open surgical repair remains the preferred option for management of infected SMA aneurysms. The typical approach is trans-peritoneal. Given well-developed collateral flow, resection without reconstruction usually suffices [6,12] and branch aneurysms can frequently be treated with simple ligation. Per and post-operative vigilance for proof of intestinal ischemia is mandatory, and reconstruction is more likely to be necessary for proximal main trunk aneurysms [3,8]. 

Endovascular options may be suitable in some cases, but open surgical resection with or without reconstruction remains the standard treatment for infected aneurysms.

Contributors: HR: manuscript writing, patient management; TR, AF, ZF: manuscript editing, patient management; ZS, BRR, BAY: critical inputs into the manuscript. HR will act as a study guarantor. All authors approved the final version of this manuscript.

Funding: None; Competing interests: None stated.