Chronic Contained Rupture of a Common Iliac Artery Aneurysm Presenting with Iliac Artery Occlusion: A Case Report

Abstract

Iliac artery aneurysm rupture usually causes acute hemorrhagic shock requiring urgent intervention, whereas chronic contained rupture is rare and seldom reported. An 86-year-old male with hypertension presented with sudden lower back and left lower limb pain causing difficulty in walking. Four weeks later, his back pain improved; however, intermittent claudication persisted. Computed tomography and magnetic resonance imaging revealed a large retroperitoneal hematoma due to rupture of the left iliac artery aneurysm and occlusion of the iliac arteries. Despite treatment recommendations, conservative management was selected in accordance with the patient’s preference. Five months later, with persistent claudication and aneurysm enlargement, endovascular treatment was performed. Using intravascular ultrasound, we crossed the true lumen and deployed a stent graft from the common to external iliac artery, achieving reperfusion without endoleak. This case report highlights the chronic course of a ruptured common iliac artery aneurysm associated with iliac artery occlusion and massive retroperitoneal hematoma.

INTRODUCTION

Rupture of iliac artery aneurysms typically presents with acute onset of lower back or abdominal pain and can be fatal because of hemorrhagic shock, necessitating urgent intervention through endovascular aneurysm repair or open surgery. Conversely, in some cases, ruptures may cause minimal symptoms and follow a more gradual course. It has been reported that approximately 4% of ruptured abdominal aortic aneurysms (AAAs) present as chronic ruptures [1]. Similar pathophysiology may apply to ruptured iliac artery aneurysms. However, differentiating retroperitoneal hematomas caused by aneurysm rupture from malignant tumors or infected aneurysms can be challenging [2].

This case involved a rare presentation of a ruptured common iliac artery aneurysm (CIAA), in which simultaneous thrombotic occlusion of both the iliac artery and the aneurysm sac led to a chronic clinical course. The complexity of this case underscores the importance of considering contained ruptures and their potential for chronic progression in patients with iliac artery aneurysms. Informed consent was given to the patient and the family for research and publication.

CASE

An 86-year-old male with a history of hypertension presented with sudden onset of lower back pain accompanied by left lower limb pain, resulting in difficulty walking. Despite the severity of symptoms, he did not seek emergency medical attention and instead managed his pain at home with analgesics. Prior to this episode, the patient had no history of intermittent claudication (IC) or other gait disturbances.

Approximately 34 days later, his lower back pain improved; however, he continued to experience IC in his left leg after walking approximately 200 m, prompting a visit to his primary care physician. Computed tomography (CT) revealed a mass in the left retroperitoneal space, leading to referral to our department 41 days after symptom onset for further evaluation of a potential vascular disorder. At the time of presentation, the patient was an active smoker, and smoking cessation was strongly encouraged.

Physical examination revealed palpable pulses in the right lower limb, including the femoral and popliteal arteries, and good pulsation in the posterior tibial artery. However, the left femoral pulse was barely palpable, and no pulses were detected below the popliteal artery. The ankle-brachial index (ABI) was 1.13 on the right and 0.51 on the left. CT imaging revealed an AAA with a maximum minor axis diameter of 33 mm and left CIAA dilated to 44 mm in minor axis diameter. Additionally, the left common and external iliac arteries (EIAs) were occluded, with a surrounding mass measuring 110×68 mm and exhibiting high CT attenuation. The left internal iliac artery (IIA) was occluded at its origin but was visualized through collateral circulation. The distal left common femoral artery (CFA) and beyond were well visualized (Fig. 1A, B).

Fig. 1.

Preoperative imaging findings. Non-contrast computed tomography (CT) showed a mass continuous with the left common iliac artery (A). Contrast-enhanced CT revealed occlusion of the left common iliac artery and a retroperitoneal mass with high CT values (B). T1-weighted magnetic resonance imaging (MRI) demonstrated a retroperitoneal mass with high signal intensity (C). T2-weighted MRI demonstrated the same mass with low signal intensity, located posterior to the distal left external iliac artery (arrowhead) (D).

The differential diagnoses included (1) left iliac artery occlusion due to retroperitoneal tumor invasion and (2) occlusion following rupture of a left iliac artery aneurysm with massive retroperitoneal hematoma. Given the sudden onset of symptoms, the latter was considered more likely.

Laboratory tests at presentation showed a hemoglobin level of 13.9 g/dL, white blood cell count of 6,130/μL, D-dimer of 1.93 U/dL, blood urea nitrogen of 12.8 mg/dL, creatinine of 0.89 mg/dL, and negative C-reactive protein, with no evidence of anemia or renal dysfunction. There was no laboratory findings strongly suggestive of infection or considerable inflammatory response, and IgG4 levels were within normal limits (12.6 mg/dL). The total prostate-specific antigen level was 232 ng/mL (free/total ratio: 0.09), whereas other tumor markers were negative.

Magnetic resonance imaging (MRI) was performed to differentiate between a tumor and hematoma, revealing a well-defined mass continuous with the left CIA; however, the left EIA was compressed and difficult to identify. T1-weighted MRI demonstrated that the retroperitoneal mass had high signal intensity. On T2-weighted MRI, the mass showed low signal intensity and was located posterior to the distal portion of the left EIA (Fig. 1C, D). Based on this assessment, further diagnostic procedures, such as positron emission tomography-CT or biopsy, were not performed.

While the diagnosis predominantly indicated a retroperitoneal hematoma following rupture of the left iliac artery aneurysm and subsequent iliac artery occlusion, the precise cause of the iliac artery occlusion remains unclear. The patient’s chief complaint was IC, and endovascular aneurysm repair was strongly recommended because of the suspicion of a ruptured CIAA. However, the patient opted for conservative management because of the minimal impact on his daily activities. He was also informed about the necessity of regular follow-ups to monitor changes in aneurysm diameter. It was emphasized that immediate intervention would be required if any significant changes were observed.

Five months after onset, the patient showed a slight improvement in claudication distance but continued to experience limitations in daily activities, prompting a desire for revascularization. Additionally, the mass, presumed to be a hematoma, had reduced in size, but the inflow from the aorta to the left CIA persisted, with an increase in the aneurysm diameter (Fig. 2A, B; maximum minor axis diameter 46 mm). Therefore, intervention for the left CIAA was planned.

Fig. 2.

Contrast-enhanced computed tomography (CT) and surgical findings 5 months post-onset. The left common iliac artery exhibited progressive expansion, with a maximum minor axis diameter of 46 mm (arrow; initially 43 mm) (A). Three-dimensional CT angiography demonstrated that the proximal 2 cm of the left common iliac artery (CIA) was normal (arrowhead), whereas the aneurysm sac was occluded by thrombus, and the distal segment of the external iliac artery (EIA) remained patent (B). An attempt to cross the occluded EIA retrogradely from the left common femoral artery (CFA) resulted in the guidewire entering the subintimal space (C). A sheath was inserted into the right CFA for an antegrade attempt, but crossing remained challenging. Consequently, a new sheath was inserted into the left CFA, and intravascular ultrasound (IVUS) guidance was employed to navigate the true lumen through the occluded EIA and aneurysmal sac in the CIA (D). IVUS-guided wire crossing was effective, allowing passage through the true lumen up to the origin of the left CIA (E), where docking with the antegrade sheath was achieved (arrowhead). Further aortography confirmed intraluminal positioning (F). Employing both antegrade and retrograde approaches, a wire was navigated through the occluded iliac artery, facilitating the placement of a stent graft (G). Completion angiography confirmed the absence of endoleak (H).

Endovascular treatment was performed under general anesthesia. A 6 Fr Brite Tip sheath (Cardinal Health) was inserted into the left CFA, and an attempt was made to retrogradely cross the occluded left iliac artery using a 0.035 Radifocus guidewire (Terumo). However, the guidewire entered the subintimal space, making the procedure challenging (Fig. 2C). A Parent Plus45 sheath (Medikit) was also inserted into the right CFA for a crossover antegrade approach, which was also challenging, with support from a 4 Fr angiographic catheter (TEMPO, Cordis Japan G.K.). A 5 Fr Super Sheath (Medikit) was inserted into the left CFA for intravascular ultrasound (IVUS) guidance (Visions PV.018, Philips). Using IVUS, the lumen of the occluded EIA was precisely identified, which was crucial given the challenging transition zone between the EIA and CIA (Fig. 2D). Determining whether the lumen within the aneurysmal sac was true or false proved challenging. However, careful attention was paid to ensure that the guidewire did not follow the subintimal space near the arterial wall margins. This careful maneuver allowed the wire to cross the CIA (Fig. 2E). After successfully crossing the left CIA, the guidewire used during IVUS was inserted into the abdominal aorta, while the crossing wire was guided into the antegrade catheter using the tip-in technique. These wires were then exchanged for catheters, and angiography was performed to confirm intraluminal positioning within the abdominal aorta (Fig. 2F, G).

The 6 Fr sheath in the left groin was replaced with a 12 Fr DRYSEAL Flex Introducer Sheath (W. L. Gore & Associates). A Gore Excluder Contralateral leg (PLC121400J, W. L. Gore & Associates) was inserted from the left CIA to the distal EIA. After post-stent graft dilation, no endoleaks were confirmed (Fig. 2H), and the left groin was closed using a Perclose ProGlide (Abbott). Postoperative ABI was 1.14 on the right and 1.06 on the left, with palpable pulses extending to the foot. Following the procedure, the patient’s IC symptoms completely resolved.

Follow-up CT 12 months postoperatively showed further reduction of the mass, which was suspected to be a hematoma, with the left CIAA clearly identified (Fig. 3A, B). The patient was lost to follow-up at his request but was admitted to another hospital for aspiration pneumonia and respiratory failure 63 months postoperatively. A contrast-enhanced CT scan at that time revealed only the remaining left CIAA, with a maximum minor axis diameter of 33 mm. The mass behind the EIA had disappeared (Fig. 3C), suggesting the possibility of a retroperitoneal hematoma due to rupture of the left CIAA. The cause of occlusion of the left EIA remains uncertain. External compression of the left iliac arteries by a massive retroperitoneal hematoma and migration of an intraluminal thrombus into the distal left iliac arteries were considered possible causes of left iliac artery occlusion at the time of rupture of the left CIAA.

Fig. 3.

Postoperative computed tomography (CT) findings. (A, B) At 12 months post-surgery, a non-contrast CT scan showed no migration of the stent graft, with a mild hematoma remaining. However, the left common iliac artery aneurysm was clearly depicted, with a maximum minor axis diameter of 36 mm (arrow). (C) At 63 months post-surgery, contrast-enhanced CT findings indicated a suspected endoleak within the left common iliac artery aneurysm, but the aneurysm sac diameter had reduced to 33 mm, and the hematoma had further decreased. The stent graft remained patent (arrow).

DISCUSSION

This is a rare presentation of a ruptured left CIAA with simultaneous occlusion of the iliac artery. The complexity of this case underscores the importance of considering contained ruptures and their potential for chronic progression in patients with iliac artery aneurysms. Chronic progression of the patient’s left CIAA was significantly influenced by occlusion of the outflow iliac artery, leading to thrombotic occlusion within the aneurysm sac. If the iliac artery had remained patent, arterial pressure within the aneurysm sac might have resulted in re-rupture [3]. The thrombotic occlusion prevents arterial pressure from affecting the rupture site and contributes to the observed chronic course. If the patient had experienced persistent lower back pain and hemorrhagic shock, emergency intervention would have been anticipated. However, the diagnosis of large retroperitoneal hematomas in the chronic phase is complex.

Sealed rupture, also known as contained rupture, is a condition in which a hematoma from a ruptured AAA is covered and stabilized by reactive changes in the surrounding tissues, as first reported in 1961 [4]. Chronic contained ruptures involve several factors: (1) known AAA, (2) previous symptoms of pain that may have resolved, (3) stable patient condition with a normal hematocrit, (4) CT showing retroperitoneal hematoma, and (5) pathological confirmation of organized hematoma [5]. This case met criteria 2-4, suggesting a high likelihood of chronic rupture.

When a retroperitoneal mass is encountered in the context of a suspected aneurysm rupture, the differential diagnoses include malignant lymphoma and bone metastases. Numerous cases of malignant tumors mimicking aneurysm rupture have been reported; therefore, malignancy should not be excluded from differential diagnoses, especially in cases involving retroperitoneal hematomas and chronically contained ruptures [2,6-8]. However, these conditions typically do not explain the sudden onset of lower limb pain, making acute arterial invasion by a tumor less likely.

As an intraoperative modality, IVUS findings do not possess sufficient diagnostic capability to differentiate between tumors and hematomas. The primary consideration for the patient’s sudden lower back and lower limb pain was iliac artery aneurysm rupture. Explaining the occlusion of the iliac artery is challenging. Although chronic AAA rupture leading to aortic occlusion has been reported, the exact cause remains unclear [9]. In this case, imaging showed a retroperitoneal hematoma compressing the EIA immediately after onset, and subsequent absorption of the hematoma revealed recanalization of the distal EIA. This suggests that the sudden formation of the retroperitoneal hematoma externally compressed and occluded the EIA. It is also possible that an intraluminal thrombus, upon rupture, migrates peripherally and forms an embolism.

The indications for revascularization in this case included the potential for aneurysm sac enlargement and the need to improve IC. As the retroperitoneal hematoma decreased in size, the left CIAA became more apparent, and arterial pressure from the aorta directly impacted the aneurysm sac, causing it to enlarge by 2-3 mm over 5 months. Consequently, a stent graft was placed between the CIA and EIA. As part of the endovascular treatment strategy, several options were considered, including bifurcated stent graft placement, use of an aorto-uni-iliac device in combination with femorofemoral bypass, and direct stent graft deployment from the CIA to EIA, which was ultimately selected. A significant anatomical limitation was the presence of bilateral inferior polar branches of the renal arteries, which arose approximately 4 cm proximal to the aortic bifurcation. Notably, the left inferior polar branch was similar in caliber to the main renal artery. Occlusion of these vessels carries a substantial risk for extensive renal infarction. Therefore, strategies involving bifurcated stent grafts or aorto-uni-iliac devices were avoided to prevent inadvertent occlusion of these critical branches, as their proximal landing zones would likely extend across them, posing a substantial risk of ischemic renal injury.

Although open surgical repair was also considered, endovascular treatment was selected according to the patient’s preference. Given the limited length of the proximal landing zone, informed consent was obtained after thoroughly explaining that the procedure would not be converted to an open surgery in the event of a type Ia endoleak.

Although a type II endoleak from the IIA was considered preoperatively, the IIA was occluded at onset, and the hematoma was reduced by the time of intervention, suggesting that clinically significant endoleaks would not occur. Therefore, wire crossing into the IIA was not attempted. At 63 months postoperatively, contrast-enhanced CT showed reduced aneurysm sac size, and only minimal contrast enhancement within the sac, indicating that long-term isolation of the aneurysm by the stent graft was maintained. Chronic contained ruptures are said to eventually cause re-rupture, although some cases remain stable over months to years, and it is better to treat regardless of the mass size [10].

In summary, a chronically contained rupture of a CIAA may present with nonspecific symptoms and remain stable because of thrombotic occlusion. However, the risks of sac expansion and re-rupture remain. This case emphasizes the importance of balancing conservative observation with timely intervention.

Funding Statement

FUNDING None.