Case No. :	80
Month :	August
Year :	2005
Contributor :	Dr. Vinay Kumar

Other Cases

A seven-year-old boy with a bicuspid aortic valve had been diagnosed to have infective endocarditis. A 2-D echocardiogram had shown multiple vegetations involving the aortic valve and the anterior leaflet of the mitral valve. The child now presented abdominal pain and breathlessness since 10 days. The abdominal pain was dull aching ,vague and intermittent in the left lumbar region associated with nausea. There were 2-3 episodes of vomiting per day since 10 days. There was history of breathlessness since 10days with history of fatigue, lethargy and decreased food intake. Bilateral inguina and cervical lymph node enlargement was noted

Ultrasonography of the abdomen showed left renal artery thrombosis for which patient was put on warfarin and heparin. Serial follow up duplex examinations of abdomen was performed. This showed development of a left renal artery aneurym

Fig. 1	Fig. 2

A CT angiogram of the abdomen confirmed the left renal artery aneurym with a small scarred, hypoperfused left kidney ( image 3,4,). Splenomegaly was also noted.

Fig.3	Fig. 4

RADIOLOGICAL Examination:

In the course of treatment, the INR was raised to 3.5. Warfarin was omitted and the patient was given Vitamin K and FFP. PT/INR become normal; however, the patient developed headache and altered sensorium. Routine blood investigations were normal except a platelet count - 80,000/cmm. A CT scan of the brain showed intracranial bleed with intraventricular extension.

Fig. 5	Fig. 6

DISCUSSION:

Mycotic aneurysm, first described over a century ago, is a serious clinical condition with significant morbidity and mortality. A mycotic aneurysm can develop either when a new aneurysm is produced by infection of the arterial wall or when a preexisting aneurysm becomes secondarily infected. The majority of mycotic aneurysms are caused by bacteria, despite the name which was coined by Osler to denote an appearance like "fresh fungus vegetations".

A mycotic aneurysm is defined as a localized, irreversible dilatation of an artery to at least one and one-half times its normal diameter - due to destruction of the vessel wall by an infection. It may be a true or false aneurysm, involving all layers or only a portion of the arterial wall.

A number of routes account for infection of an arterial wall including:

• Septic emboli to the vasa vasorum
• Contiguous infective focus extending to the arterial wall
• Direct bacterial inoculation at the time of trauma, such as a penetrating injury
• Bacteremic seeding of an existing intimal injury or atherosclerotic plaque.
  

Mycotic aneurysms can occur anywhere in the body. In one series, 31 percent were abdominal aortic, 38 percent femoral, 8 percent superior mesenteric, 5 percent carotid, 6 percent iliac, and 7 percent brachial. Mycotic aneurysm involving renal arteries are very rare.

The organisms implicated vary according to location. The most likely organisms involved in cases of suprarenal aneurysms are gram-negative rods, especially Salmonella spp. Overall, gram-positive organisms account for 60% of mycotic aneurysms, Staphylococcus aureus and Streptococcus spp. occurring in 46% and 8% of cases respectively. In the pre-antibiotic era, Streptococcus pneumoniae was often implicated in subacute bacterial endocarditis.7 Today, mycotic aortic aneurysms due to this organism are rare.

Predisposition - Risk factors for mycotic aneurysms have been described. In two retrospective reviews, the common risk factors were:

• Arterial trauma - Self-induced, iatrogenic, or accidental trauma to the artery resulted in 29 to 42 percent of cases. Injection drug use (IDU) was frequent, and infection usually involved the femoral vessels in these patients. Bacteria can be introduced directly into the arterial wall or into a surrounding hematoma at the time of the initial or subsequent injection, resulting in a mycotic aneurysm. A mycotic aneurysm has also been a complication of percutaneous coronary and femoral arterial angiography.
• Bacterial endocarditis - The majority of mycotic aneurysms occurred in patients with endocarditis in the preantibiotic era.
• Local or concurrent infection was present in five and 17 percent of patients.
• Impaired immunity - In one series, diabetes, alcoholism, corticosteroids, chemotherapy, and malignancy were identified as possible risk factors in 24 percent of patients. · Age - Salmonella septicemia is most likely to result in salmonella aortitis in the elderly who have a higher incidence of atheromatous plaques.
  
  

A mycotic aneurysm usually has a saccular, irregular contour, and it contains little or no mural calcification. It enhances to a degree similar to the adjacent normal appearing aorta. The diagnosis can be confidently made based on CT findings if gas is seen within the wall of the aorta. Additional features that often aid in the diagnosis include splenic infarcts, lack of atherosclerotic changes in the other vessels, and the rapidity of its appearance. A nonenhancing periaortic mass representing inflammatory tissue and blood from a contained aortic rupture may be present. In chronic forms, erosion of the adjacent vertebral body and a paravertebral soft-tissue mass may be identified. Intracranially they occur usually in the distal branches at branching points.

The general principles of management involve both antimicrobial therapy and surgery. Drainage and wide débridement of all devitalized tissues with thorough revascularization in situ or extra-anatomic bypass grafting are necessary. Life threating haemorrhage is the most dreaded complication with a 67 % mortality rate. The results after treatment of infected aneurysms have improved over the years because of prompt diagnosis, improved surgical techniques and advances in antimicrobial therapy. Today, the death rate related to suprarenal mycotic aneurysms is estimated to be 13%.

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