Ruptured internal iliac artery aneurysm

Clinical History

The patient was admitted in the emergency department due to sudden onset severe abdominal pain, especially in the left flank.

Imaging Findings

As a ureteral calculus was suspected an unenhanced CT of the abdomen was performed first. A large retroperitoneal heterogeneous mass was seen in the pelvis and both flanks (Figure 1a-d). Furthermore, left-sided hydronephrosis was present due to distal ureteral compression from the large mass (Figure 1e). A ruptured iliac artery aneurysm with large retroperitoneal haematoma was suspected and dual-phase CT angiography (CTA) was performed (Figures 2-4). CTA showed a 10 cm ruptured left-sided internal iliac artery aneurysm. Active bleeding was present with contrast extravasation anterior to the aneurysm (Figure 3a). Extensive retroperitoneal haematomas were present mostly on the left side. There were only minimal amounts of free fluid (Figure 3b). The aorta showed elongation and kinking (Figure 4) but no aneurysm.
The case had a fatal outcome as the patient died from hypovolemic shock before surgery or endovascular repair could be performed.

Discussion

Isolated internal iliac artery aneurysm (IIIAA) is a rare condition. Most of the patients are aged between 65-70 years at presentation. There is a strong male predominance with the male female ratio of 7:1 [1]. Like abdominal aortic aneurysm the most common cause of IIIAA is atherosclerosis [2]. Other causes are trauma, infection, pregnancy, traumatic childbirth or Caesarean section, Marfan and Ehlers-Danlos syndromes, fibromuscular dysplasia, and other connective tissue diseases [3].

The majority of patients with IIIAA are asymptomatic until aneurysm rupture [1]. In aortic aneurysms signs and symptoms of rupture are abdominal pain and haemodynamic instability [4].
However, IIIAA may also cause symptoms due to compression of adjacent structures or fistulation [5]. Urological symptoms due to ureteral and/or bladder compression are common and can result in hydronephrosis, urinary retention, pulsatile micturition, ureteric colic, pyelonephritis, and renal failure [3]. Compression of the colorectal region may cause pain on defecation or constipation [6].

CTA is the method of choice for detection and characterization of abdominal aneurysms including IIIAA. With CTA aneurysm site, size, and relation to other structures can be evaluated [7]. CTA also shows extra-vascular injuries and haematomas. Multiplanar and 3D reconstructions from CTA are important in pre-treatment planning before surgery or endovascular repair of IIIAA. Extravasation of contrast media is present during active bleeding.
Contrast-enhanced MR angiography (CE-MRA) performs well in detection of IIIAA [3]. However, CE-MRA has only a minor role in the acute setting.
Doppler ultrasound can also be used to detect IIIAA. The main advantage of ultrasound is the wide availability and flexibility of this imaging procedure. Disadvantages include large operator-dependency, limited views of the internal iliac artery due to deep location in the pelvis or overlying bowel gas. Vessel tortuosity may also be problematic [8].

Treatment options for IIIAA are open surgery or endovascular repair. In patients with comorbidities endovascular repair is often preferred, as this procedure is less invasive than open surgery.
IIIAA with compressive symptoms should be treated with open surgery because this can rapidly reduce the aneurysm size [5].

Differential Diagnosis List

Final Diagnosis

Ruptured internal iliac artery aneurysm

URL:	https://www.eurorad.org/case/11413
DOI:	10.1594/EURORAD/CASE.11413
ISSN:	1563-4086