Mycotic aneurysm

Case contributed by Paul Simkin


Fever and previously infected renal transplant. New back pain.

Patient Data

Age: 70 years
Gender: Male

A 12 x 10 x 9 mm eccentric aneurysm is seen extending anterolaterally from the right side of the abdominal aorta, 1.5 cm distal to the superior mesenteric artery. This may be at the level of the right renal artery. There is significant surrounding fat stranding. The aneurysm was not present on CT.

Left iliac fossa transplant nephrectomy is noted. The previously identified well-defined collection in the surgical bed has resolved with residual fat stranding and thickening of the overlying anterior abdominal musculature. No new intra-abdominal collection is seen. No free fluid or gas.

There is progressive increased splenomegaly with a craniocaudal diameter of 13.6 cm ( previously measures 11.2 cm ). Several regions of peripheral hypoattenuation are identified, possibly still technical. No perisplenic hematoma or collection. There is normal attenuation of the splenic artery and vein.

Both kidneys are atrophic. The liver (partially imaged ) is enlarged. Pancreas and adrenals are unremarkable.

The bowel is within normal limits.

No inguinal or intra-abdominal lymphadenopathy.

Minor bibasal atelectasis/scarring.

Normal lumbar vertebral body height and alignment is maintained. Bones appear osteopenic. No acute fracture identified. The prevertebral and paravertebral soft tissues are unremarkable.


The appearances are concerning for a mycotic aneurysm, at the origin of the native right renal artery. Vascular referral recommended. Unit notified.

Bilateral fusiform dilatation of the common iliac arteries also noted.

Hepatosplenomegaly, non-specific, but a lymphoproliferative disorder including lymphoma needs to be considered.

No intra-abdominal collection identified.



Previous comparison study, showing absence of the now-suspected mycotic aneurysm. The complete report is included below for reference.

The well-defined collection at the surgical bed in the left iliac fossa, with a well-defined pseudocapsule is moderately smaller in size, measuring 6.2 x 5.8 x 3.7 cm. This is located in the retroperitoneum, adjacent to the uninvolved left iliac vessels and psoas muscle, with a small track into the overlying muscle and subcutaneous fat, but the subcutaneous component seen previously has resolved. This collection does not extend deeper into the pelvis or retroperitoneum.

Extensive vascular calcification seen throughout without major arterial stenosis. The liver, mild splenomegaly, pancreas, adrenal glands and severely atrophied kidneys are unremarkable. No ascites.


Significant remnant collection/mass in the old left renal graft pseudocapsule.


Case Discussion

The aneurysm at the origin of the previously thrombosed right renal artery has a saccular or eccentric morphology, which is unusual for aorta aneurysms. This, combined with the history or recently infected renal transplant, should raise the suspicious of mycotic aneurysm.

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