Aortic pseudoaneurysms (PAs) are abnormal outpouchings or dilatations of the aorta without all three layers of the arterial wall and typically occur as complications of endovascular intervention, surgery, or trauma. Although rare, some cases have reported non-traumatic pathologies, such as infection and penetrating atherosclerotic ulcers. The rupture of such PAs has morbid consequences, potentially causing massive bleeding. The rates of rupture were correlated with the increasing PA size.

Here, we present a case of a PA detected incidentally in a male patient who experienced blunt abdominal trauma 30 years before presentation. The study was approved by the Institutional Review Board of the Seoul National University Hospital (IRB no. 2102-107-1197).

An 83-year-old male presented to our hospital with incidental findings on an abdominal computed tomography (CT) scan, conducted for the evaluation of a right-sided inguinal hernia for a few months. The scan revealed a 9.2 cm heterogeneously attenuating mass just below the aortic bifurcation level, extending into the pelvis and situated adjacent to the aorta, small bowel, and sigmoid colon. The initial suspicion centered around a mesenteric tumor, gastrointestinal stromal tumor, or sarcoma (Fig. 1).

Figure 1. The mass lesion was initially considered a mesenchymal tumor of small bowel origin.

He had a history of blunt abdominal injury caused by a steering wheel during a car crash 30 years prior. This incident led to signs of peritonitis, a diagnosis of bowel perforation, and subsequent bowel resection. Postoperatively, the patient was not informed of any abnormalities in the aorta or other vasculature. The patient recovered well without any postoperative complications. He was a nonsmoker and was currently taking medications for hypertension, diabetes, and dyslipidemia.

On initial examination, the patient was hemodynamically stable and afebrile. A large, fixed, round mass was palpable in the suprapubic area, but it was neither tender nor pulsatile. Laboratory tests revealed no abnormalities. The patient denied having obstructive gastrointestinal symptoms. The formal CT reading indicated a likelihood of aortic PA, as the mass was observed communicating with the aortic bifurcation, connected by a neck-like structure (Fig. 2).

Figure 2. A short communication between the aortic bifurcation and the thrombus-filled aortic pseudoaneurysm was displayed.

We planned surgical repair using an interposition graft because sac excision or thrombus evacuation appeared beneficial for reducing the size of the mass. This approach aimed to prevent potential infectious or obstructive complications in cases the mass remains. The patient was in good general condition, had no severe comorbidities, and was fit for surgery. Additionally, the patient required surgical repair for a right inguinal hernia.

A midline transperitoneal approach was used to assess the retroperitoneum and visualize the aortic bifurcation. Significant adhesion of the lesion to the small bowel mesentery, ascending colon, and sigmoid colon was observed (Fig. 3), which required extensive dissection and adhesiolysis. Upon full visualization, the lesion communicated through the aortic bifurcation. Moreover, it was non-pulsatile, exhibited very hard texture, had a very thick wall, and showed no signs of infection or rupture.

Figure 3. The operative picture showed the pseudoaneurysm with severe adhesion to the ventral sigmoid colon.

We then exposed the proximal aorta and iliac vessels, which were clamped after systemic heparinization, before opening the PA and removing the thrombus. A Dacron 16-8 mm graft was used as an aorto-biiliac interposition graft, proximally anastomosed to the infrarenal aorta and distally to the right internal iliac artery (with the external iliac artery reimplanted to the side of the graft) and the left common iliac artery (CIA). The PA was not fully excised because the adhesion of the PA to the sigmoid colon and retroperitoneal venous plexus was too severe to cause bowel injury or uncontrolled bleeding upon further dissection. The PA sac was closed using continuous Vicryl sutures and reperitonealized. The right inguinal hernia was repaired, and the abdominal wall was closed. Pathological reports confirmed the presence of a PA wall with dystrophic calcification, myxoid degeneration, and a mural thrombus. Tissue cultures revealed no microorganisms.

The patient was started on an oral diet on the 2nd postoperative day and was discharged without any complications on the 8th day. Postoperative follow-up CT revealed a residual collapsed sac (Fig. 4) and patent interposition graft (Fig. 5).

Figure 4. Postoperative computed tomography scan displayed the bifurcation site and residual aortic pseudoaneurysm sac.

Figure 5. Postoperative computed tomography scan displayed the maximum intensity projection image of the reconstructed aortoiliac bifurcation.

Abdominal aortic PAs are very rare in incidence but pose a serious threat with potentially fatal outcomes. They typically results from injury to the aortic wall, commonly post-surgical (trocar injuries or surgeries of structures adjacent to the aorta, such as the vertebral body) or traumatic. Other pathophysiologies such as severe pancreatitis, infection, or systemic conditions like Bechet disease, can also contribute to their formation [1]. Blunt trauma to the aorta may cause intimal disruption, intramural hematoma, or PA formation [2]. Two mechanisms of blunt aortic injury have been proposed: retroperitoneal hematoma formation resulting from avulsion of the aortic branches and secondary aortic thrombosis from intimal tearing [3], with the latter being more common, as noted in a review of 60 patients with blunt aortic injuries [4,5].

PAs originating from major intra-abdominal vessels may remain asymptomatic until symptoms arise from the mass effect (due to the extrinsic compression of adjacent structures) or rupture. Symptoms may include back pain, abdominal pain, a palpable pulsatile abdominal mass, gastrointestinal bleeding, and thromboembolism [6]. Compressive symptoms such as biliary obstruction [6], acute aortic or iliac occlusion [7], renovascular hypertension [8], and compression of the vena cava may also arise [9].

The time interval between PA formation and vascular insult (such as arterial puncture or surgery) has varied in previous case reports, ranging from immediate to a maximum of 42 years [10]. In this case, the precise time required for PA formation was unclear.

Abdominal aortic injuries from blunt trauma are rare, probably because of the retroperitoneal location just anterior to the vertebrae and surrounding visceral organs. However, they are more commonly associated with penetrating abdominal trauma, while thoracic aortic injuries are frequently seen in cases of blunt trauma [11]. Two studies evaluating the autopsy results of blunt trauma patients reported an abdominal aortic injury rate of 4.6% [12,13]. Our patient experienced blunt trauma and underwent abdominal surgery 30 years ago without any mention of injury to the aortic bifurcation, and also had moderate atherosclerosis of the infrarenal aorta. Upon surgical exploration, the PA wall was thick, calcified, and surrounded by adjacent bowels. As a cause of PA in our patient, a minor traumatic dissection occurred, and the PA grew slowly due to the relatively thick fibrous tissue around; however, we also suspected that a recently ruptured ulcerated atherosclerotic plaque may have been the cause. The patient had multiple vascular risk factors and a profuse atheroma near the lesion. Previous studies have reported PAs caused by ruptured atherosclerotic plaques in the abdominal and thoracic aorta [14,15]. The likelihood of a 9 cm PA at such a high-pressure site of the aortic bifurcation growing gradually over the last 30 years without rupture seems unlikely. Nonetheless, the patient had minimal insight into his previous medical condition and could not provide any previous imaging studies, limiting the discussion in this area.

As aortic PAs are rarely diagnosed, the initial diagnosis may be difficult and dependent on imaging studies, such as contrast-enhanced CT scans. Furthermore, CT can identify the precise location and anatomy of a lesion and its relationship with adjacent structures, thereby guiding treatment planning, such as surgery or endovascular intervention. Additionally, CT is also less invasive than aortography and is readily available in most healthcare institutions. With its high sensitivity, most cases of aortic PAs are diagnosed using CT alone [10]. In our case, the PA had heterogeneously attenuated contents and abutted the small bowel, initially mimicking a mass of bowel origin, resulting in a difficult diagnosis. When the diagnosis of PA is uncertain, a duplex ultrasonographic scan may prove useful for determining the presence of arterial flow within the sac. However, our patient’s PA was completely thrombosed and filled with thick paste-like thrombi and dense atheroma; therefore, the lesion was likely to be negative on a duplex scan.

In a typical scenario, this patient could be referred to the gastroenterology or oncology department if the initial diagnosis of a mesenteric tumor was suspected. This is crucial because a gastroenterologist or oncologist will perform an endoscopy or biopsy to diagnose the patient. This results in a delay in diagnosis and may cause complications, such as hemorrhage, following a biopsy. Therefore, a high index of suspicion is important.

The treatment of PAs aims to minimize the risk of rupture and relieve symptoms if present. Surgeries such as primary aortorrhaphy [11], patch aortoplasty [2], resection and graft interposition may be performed. In previous reports, resection and graft interposition were preferred for young patients with tolerable PAs [16]. In this case, excision of the PA and primary closure or patch angioplasty were impossible due to heavy calcification at the aortic bifurcation, which may have been the cause of the PA.

On the other hand, patients with a high perioperative risk, such as old age, severe comorbidities, and a history of multiple abdominal surgeries, may benefit from the endovascular approach with less complication risk [17]. First described by Parodi in his review in 1996, endovascular interventions have been increasingly performed using stent grafts (endovascular aneurysm repair [EVAR]) to exclude PAs of the infrarenal aorta or embolize the PA itself [18]. Looking back upon this case, this 83-year-old patient may have been a good candidate for EVAR. In addition, a case of ruptured aortic PA near the aortic bifurcation that was treated successfully with EVAR has been reported [19]. However, we could not completely dismiss the possibility of a mass lesion originating from bowel or mesentery; thus, open surgery with graft interposition was performed after exploration. Moreover, the diameters of aortic bifurcation, right CIA, and left CIA were 16, 9.5, and 9 mm, respectively. Implantation of a stent graft was considered to be risky or impossible because of a narrow aorta. In addition, surgical treatment of the hernia was planned, and the patient could not avoid the procedure. Another hybrid option is EVAR with an aorto-uni-iliac device, femoral-femoral bypass, and embolization of the contralateral CIA because of the possibility of a hostile abdomen resulting from a previous operation. However, the long-term patency of the extra-anatomical bypass was not sufficient, and the patient had an inguinal hernia to be repaired; therefore, we opted for open repair. The preoperative evaluation demonstrated that the patient was not at high risk for surgery.

Whether this patient was indicated for treatment remains unclear. If chronic, a completely thrombosed PA may not have had a high risk of rupture. However, the large size (9.2 cm) and high-pressure location of the lesion, along with the possibility of a delayed rupture, which would have proven fatal in a patient of this age, led us to believe that aggressive management was indicated. A similar case of aortic PA at the aortic bifurcation reported a delayed rupture after 14 years, although this seemed to be due to a lack of imaging evidence of PA immediately after traumatic injury [20].

In conclusion, masses with atypical characteristics near the aortic bifurcation should be approached carefully. Although scarcely reported, the possibility of aortic PA should be considered if related imaging findings or histories are suspected, underscoring a high index of suspicion. Such PAs can be safely managed by surgical repair or EVAR.

None.

Seung-Kee Min have been the editorial board member of the VSI since 2019. He was not involved in the review process. Otherwise, no potential conflict of interest relevant to this article was reported.

Concept and design: SKM. Analysis and interpretation: JHP, HYW. Data collection: JHP. Writing the article: JHP, SKM. Critical revision of the article: HYW. Final approval of the article: all authors. Statistical analysis: none. Obtained funding: none. Overall responsibility: SKM.