ACRT Journal

Background

False aneurysm (pseudoaneurysm) is defined as a hematoma with pulsatile flow inside, which progresses into a pulsatile vascular mass. It subsequently forms an aneurysmal sac whose wall is composed of surrounding tissues and connective tissue adjacent to the hematoma. The walls of the aneurysm sac lack histological elements of an arterial wall. Its expansion often requires intervention. Direct thrombin injection is indicated for narrownecked aneurysmal sacs, minimizing the risk of embolization. Surgery is reserved for wide-necked pseudoaneurysm, in the absence of required materials and structure for thrombin injections, or in cases involving prosthetic grafts. The most common sites of pseudoaneurysm formation include the femoral, brachial, radial, and subclavian arteries, as well as distal anastomoses of an aortofemoral bypass. Pseudoaneurysms result from complete rupture of the arterial wall, creating direct communication between the arterial lumen and the pulsatile hematoma resulting from arterial injury [1]. Anastomotic pseudoaneurysms may occur in arterial grafts due to suture line dehiscence, often secondary to arterial wall weakening. In the presence of infection, they are also called infected pseudoaneurysms. The term pseudoaneurysm applies because the lesion is not lined by the three layers of the arterial wall, unlike true aneurysms, but rather by a fibrous capsule formed around the perianastomotic hematoma, which prevents immediate bleeding. Possible complications include pain, rupture, hypovolemic shock, distal embolization, neuropathy, and skin necrosis [1].

Unilateral axillofemoral bypass was first described by Louw in 1962 [2,3] as a treatment for occlusive arterial disease. Extraanatomic bypass routes should be reserved for patients whose poor general health or specific local conditions preclude the use of a traditional access route or aortofemoral bypass. Cardiac, renal, or pulmonary comorbidities may make abdominal surgery unacceptably risky. Axillobifemoral bypass, when performed with a ringed prosthesis, shows primary patency rates similar to those of aortofemoral grafts at five years [4]. The technique involves anastomosing the prosthesis to the subclavian artery, tunneling it beneath the pectoralis major, then subcutaneously along the midaxillary line, across the anterior superior iliac spine, and then to the femoral artery. The distal anastomosis is performed on the common femoral artery or, if it is occluded, directly on the deep femoral artery [1]. Extra-anatomical bypass is considered the revascularization method of choice for limb salvage in patients with infrarenal aortoiliac occlusion and severe comorbidities [5]. The primary objective of the report is to raise awareness among the medical community about the possibility of spontaneous pseudoaneurysm formation in synthetic materials. The secondary objectives are to demonstrate that open surgical techniques remain relevant, to identify the best management strategy for such cases, and to explore possible causes.

Case Report

This article reports on a case that was followed for fourteen months, involving pseudoaneurysm formation in a Dacron graft used for femorofemoral crossover bypass and a subsequent second pseudoaneurysm after endovascular reconstruction of the same bypass. An 81-year-old man, non-diabetic, presented to the emergency department at a private hospital in the city of João Pessoa, PB, Brazil, on November 16, 2023, with a sudden onset of a bulge in the suprapubic region and mild local pain. He denied a history of local trauma. There was no hypotension, skin lesions, signs of inflammation, or signs of lower limb ischemia. However, he reported undergoing abdominal aortic aneurysm repair approximately ten years earlier using a left-sided monoiliac Dacron graft (due to right iliac obstruction; Figure 2) and a femorofemoral crossover bypass using Dacron. Computed tomography (CT) angiography (November 16, 2023) revealed a contained rupture of the Dacron femorofemoral crossover bypass, forming a pseudoaneurysm and a suprapubic hematoma measuring 14.8 × 14.9 × 9.6 cm (Figure 1 and Table 1).

Table 1: CT angiography of the abdominal aorta.

Figure 1: Contained rupture of a pseudoaneurysm in a femorofemoral crossover bypass in the suprapubic region at admission (November 16, 2023). Yellow Arrow - Large Hematoma, Red Arrow - Dacron Bypass rupture. (Personal archive)

Figure 2: Occlusion of the right iliac arteries on the day of admission (November 16, 2023). Yellow Arrow – occlusion of the right iliac arteries (Personal archive)

Endovascular repair was performed using three Viabahn segments, as a single appropriately sized endoprosthesis was unavailable due to logistical limitations in the state of Paraíba. The hematoma was initially left in place for observation and potential drainage. A color Doppler ultrasound performed 24 hours postoperatively showed no abnormalities in the endoprostheses of the new femorofemoral bypass and normal perfusion of the lower limbs. On inspection, there were no signs of inflammation, and popliteal pulses were present. On November 20, 2023, percutaneous drainage was performed because the hematoma persisted. Complete drainage was not possible due to the presence of firm clots. To minimize the risk of endoprosthesis exposure, the incision was limited to 3 cm. On December 29, 2023, a repeat color Doppler ultrasound of the aorta, iliac arteries, and lower limbs revealed diffuse atheromatosis, hematoma persistence, right anterior tibial artery occlusion, and a patent bypass without endoleaks (Tables 2 and 3).

Table 2: Arterial Doppler ultrasound of the lower limbs

Table 3: Arterial color Doppler ultrasound of the aorta and iliac arteries

On February 14, 2024, pelvic CT angiography with contrast (Table 4) confirmed the absence of endoleaks, patency of the bypass, and persistence of the hematoma, resulting in a non-pulsatile suprapubic bulge. Physical examination revealed dark sanguinolent secretion from the percutaneous drain, with no signs of inflammation or fever. The drain remained in place until June 3, 2024, when a new rupture occurred in the femorofemoral bypass with endoprosthesis. Intraoperatively, there was no endoprosthesis disconnection, but an active bleeding site was identified and corrected. The tortuous segment of the endoprosthesis was resected, and end-to-end anastomosis was performed. The entire hematoma was excised, followed by thorough irrigation with 0.9% saline and primary closure of the surgical wound in deep and superficial layers. The patient was discharged seven days after the surgery. However, on July 20, 2024, he was readmitted with wound dehiscence and endoprosthesis exposure through the surgical wound (Figures 3 and 4).

Table 4: Contrast-enhanced pelvic CT.

Figure 3: CT scan showing exposure of the femorofemoral crossover bypass endoprosthesis. Yellow arrows – externalization of the endoprosthesis, Red arrows – endoprosthesis in the deep subcutaneous tissue. (Personal archive)

Figure 4: Externalization of the endoprosthesis through dehiscence of the surgical wound (suprapubic region). Red arrow – exteriorization of the endoprosthesis, the endoprosthesis stent mesh can be seen. (Personal archive).

The femorofemoral crossover bypass was explanted and replaced with a right axillofemoral bypass using a 6 mm × 70 cm ringed Polytetrafluoroethylene (PTFE) prosthesis. Intraoperatively, we identified the complete wear of the Dacron graft used in the first femorofemoral bypass. A segment of the exposed endoprosthesis was sent for culture and antibiogram (July 20, 2024), which isolated Morganella morganii subsp. morganii, a Gram-negative bacterium. On December 11, 2024, arterial color Doppler ultrasound of the right lower and upper limbs confirmed patent right axillofemoral bypass, diffuse atheromatosis in both limbs, and the right lower limb, and monophasic flow in the right anterior tibial and dorsalis pedis arteries. No endoleaks or pseudoaneurysms were detected (Table 5). At follow-up on January 9, 2025, the patient was afebrile, conscious, alert, and oriented, with good perfusion of the lower limbs and no evidence of flow steal from the right upper limb. No hematomas were observed.

Table 5: Arterial Doppler ultrasound of the right upper and lower limbs and right axillofemoral bypass.