A 38 year-old man presented with left upper quadrant (LUQ) pain radiating to the shoulder. Two weeks prior, he was evaluated for arthralgias, malaise, and intermittent “black spots” in his vision. Physical exam revealed a III/VI decrescendo murmur at the apex and severe LUQ tenderness with rebound and guarding. There was no ascites, palpable spleen tip, or abdominal bruit.
On transthoracic echocardiogram, there were no valvular vegetations but mild mitral regurgitation. CT angiogram revealed a large splenic infarct, and multiple arterially-enhancing foci consistent with pseudoaneurysms with extravasation of contrast concerning for rupture.
His medical record revealed a history of IV drug use and recent mitral valve infective endocarditis (IE), which was incompletely treated. Blood cultures from his clinic visit grew viridans streptococci. The day after admission, the patient underwent splenic artery embolization followed by open splenectomy. Pathology confirmed splenic artery mycotic aneurysm with abscess, infarct, and hemorrhage.
The splenic artery is the most frequent site for development of visceral artery aneurysms, accounting for 60% of all cases. Etiologies include atherosclerosis, fibrodysplasia, penetrating trauma, connective tissue diseases, pregnancy, and infection.
Embolic phenomena complicating IE are well described, occurring in up to 44% of cases. While up to 38% of asymptomatic patients with IE have splenic infarcts, less than 10 cases of mycotic splenic artery pseudoaneurysms have been reported. Causative organisms have included streptococcus, staphylococcus, actinomyces, and cases of sterile blood cultures.
In 1885, Sir William Osler first described a “mycotic aneurysm” associated with IE. Pathogenic mechanisms include septic embolization, hematogenous seeding, and direct inoculation. Infected aneurysms grow rapidly and have a high risk of rupture, which carries a 75% mortality. As such, early diagnosis and management is key to patient survival.
CT angiography is the recommended imaging modality to investigate infected aneurysms, which can be asymptomatic and multifocal. There should be a low threshold to investigate the integrity of the head.
Apart from antibiotics, treatment of mycotic splenic artery aneurysms is largely surgical. Options include ligation and excision, transcatheter embolization, and endovascular stent grafts. The latter are less favored due to retained septic foci. In this case, transcatheter embolization was performed for proximal control prior to definitive treatment with splenectomy.
Complications of IE in viscera such as the spleen include infarct, abscess formation, and mycotic aneurysms. Although uncommon, infected splenic artery aneurysms are important IE sequelae to consider given their proclivity for rapid expansion and rupture, carrying a high mortality rate. CT angiogram is the imaging modality of choice, and management is largely surgical.
To cite this abstract:Fung M, Ronan M. A Deep-Seated Time Bomb. Abstract published at Hospital Medicine 2015, March 29-April 1, National Harbor, Md. Abstract 519. Journal of Hospital Medicine. 2015; 10 (suppl 2). https://www.shmabstracts.com/abstract/a-deep-seated-time-bomb/. Accessed March 30, 2020.