Uretero-hydronephrosis caused by an internal iliac artery aneurysm

Clinical History

A 54-year old male presented to our institution's emergency department with right abdominal and lumbar pain. He carried a recent ultrasound exam showing a right uretero-hydronephrosis. A computed tomography (CT) was performed.

Imaging Findings

The CT confirmed the right uretero-hydronephrosis with an anteroposterior diameter of the renal pelvis of 30 mm (figure 1). There were no renal or ureteric stones.
A right internal iliac artery aneurysm measuring 85 mm x 80 mm was depicted (figure 2), and the right ureter was dilated to the level of the right internal iliac aneurysm (figure 3), which was assumed to be the cause of the obstruction.
A smaller left internal iliac artery aneurysm was also shown, as well as an abdominal aortic aneurysm.

Discussion

A. Background
Internal iliac artery aneurysms (IIAA) are rare and are usually associated with aortic aneurysms. When in conjunction with an aneurysm of the abdominal aorta the incidence is approximately 10% [1].
An isolated IIAA is defined as an at least two-fold increase in the artery's diameter without a coexisting aneurysm in other location [2]. It has an incidence of 0.4%, being more common in elderly males aged 65-70 [3]. They are bilateral in up to 50% of the cases [1].
IIAAs are more frequently caused by degenerative changes associated with atherosclerosis [4], however, there are other possible causes such as infection, trauma, pregnancy/delivery, connective tissue disorders, and arterial wall diseases [3].

B. Clinical Perspective
IIAA are usually asymptomatic, due to the deep location of the internal iliac artery. However, as they increase in size, they can rupture or compress adjacent structures, triggering urological, gastroenterological and neurological symptoms [1, 5].
Urological complications may include hematuria, bladder outlet obstruction [1] and ureter obstruction with subsequent hydronephrosis, which may result in pyelonephritis or renal failure [2].
Rupture is the most severe complication, as it is associated with a high mortality rate ranging from 50% to 100% [2, 3].

C. Imaging Perspective
Angio-CT is the gold standard for the diagnosis of an aneurysm, showing its location, size, signs of complication and relation with adjacent organs [4].
Contrast- or non-contrast enhanced Angio-MRI may be used in selected patients, especially those who have iodine contrast administration contraindication [4].
Plain radiographs of the abdomen and pelvis may show the calcified wall of an aneurysm, but their usefulness is limited [3].
Ultrasound is useful in an initial investigation as it depicts the uretero-hydronephrosis and other renal complications. With colour-flow Doppler, the blood flow within an aneurysm can be confirmed [3].

D. Outcome
Surgery is indicated when the patient is symptomatic, or an aneurysm is expanding or is greater than 3 cm, providing that the patient has a reasonable clinical condition [1, 4].
For patients without clinical conditions for open surgery, the options are embolization and stent-graft placement [1].
This patient had surgery of embolization of the right external iliac artery, which retrogradely fed the internal iliac artery aneurysm. Ureteral stent was placed on the right ureter.

E. Take Home Message, Teaching Points
- Isolated internal iliac artery aneurysms are rare and usually asymptomatic.
- As they increase in size, they can rupture or cause compression in adjacent structures.
- One of the possible complications is ureter obstruction with subsequent uretero-hydronephrosis.

Written informed patient consent for publication has been obtained.

Differential Diagnosis List

Final Diagnosis

Uretero-hydronephrosis caused by internal iliac artery aneurysm.

URL:	https://eurorad.org/case/16361
DOI:	10.1594/EURORAD/CASE.16361
ISSN:	1563-4086