Giant Dorsalis Pedis Pseudoaneurysm Following Cannulation for Arterial Line in a Patient with Systemic Lupus Erythematosus

Abstract

Dorsalis pedis artery (DPA) aneurysms are very rare and fewer than 60 cases have been reported in the literature. Most affected patients present with false aneurysms after orthopedic surgery or trauma. Here we report an unusual case of a giant DPA pseudoaneurysm after cannulation for arterial line placement in a patient newly diagnosed with systemic lupus erythematosus (SLE). A diagnostic delay resulted in necrosis of the overlying skin. Excision of the pseudoaneurysm, ligation of the DPA, and debridement of the foot dorsum were performed, followed by a second flap coverage surgery. Although a DPA false aneurysm is rare after arterial line removal, it can cause the serious complications of skin necrosis, rupture and toe necrosis. Arterial puncture sites should be carefully monitored, especially in patients with SLE or other vasculitis.

INTRODUCTION

Dorsalis pedis arter y (DPA) aneurysms represent a small proportion of peripheral artery aneurysms, with an estimated incidence of 0.5% [1]. An extensive literature review revealed fewer than 60 cases published to date [2]. However, its actual incidence may be underestimated because smaller aneurysms treated conservatively are rarely reported. The causes of pseudoaneurysms are usually iatrogenic or community trauma. However, in some perplexing cases, connective tissue disease or vasculitis can cause peripheral pseudoaneurysms. A detailed recording of the patient’s medical history and a careful physical examination are needed to reveal the underlying cause. Marfan syndrome and Ehlers–Danlos syndrome frequently accompany arterial aneurysms, especially those within the aorta [3]. In some studies, one third of these patients also present with peripheral artery aneurysms [3,4]. An association between peripheral artery aneurysm and vasculitis has also been suggested although data regarding systemic lupus erythematosus (SLE) remain sparse [5]. The treatment of foot pseudoaneurysms traditionally includes observation or open surgery since there is an adequate collateral network in most cases. Thrombin injection and endovascular procedures have been added to the panel of therapeutic approaches during the past few decades [1,5,6].

Aims of this report are to investigate the proper management of a giant pseudoaneurysm and evaluate a possible correlation between SLE and peripheral artery aneurysm formation.

CASE

A 51-year-old female patient was admitted to the neurology department with ischemic stroke. The primary cause, a spontaneous left vertebral artery dissection, was the first clinical manifestation of SLE in this patient. She presented with a gradually enlarging mass on the dorsum of her left foot, which was detected 1 week after the removal of an arterial line (A-line). She had a history of bilateral mastectomy and radiotherapy for breast cancer 4 years prior. To treat the dissection, she was administered aspirin 100 mg daily and bemiparin sodium 3,500 IU/0.2 mL daily. A physical examination revealed a large pulsatile mass with necrosis of the overlying skin (Fig. 1), but no signs of infection, peripheral ischemia (normal Doppler signals in all digital arteries), or palpable thrill. The color duplex scan showed the typical “yin-yang” sign (bi-directional flow due to the swirling of blood within the collection, confirming the diagnosis of a false aneurysm (4.0×4.0×8.0 cm) with a wide neck (6 mm) originating from the left DPA (Fig. 2). The posterior tibial and plantar arteries were patent with normal velocities (60–80 cm/sec), without any sign of atherosclerosis.

Fig. 1.

Preoperative clinical evaluation revealed a giant mass on the dorsum with skin necrosis.

Fig. 2.

Duplex ultrasonography performed with a Philips Affiniti 30. (A) B-mode image shows an anechoic, longitudinal mass with blood elements flowing and swirling within a collection. (B) Color Doppler image shows blood spreading from the dorsalis pedis artery to the surrounding tissue with a wide neck.

Open surgical repair was selected as the most appropriate approach due to the skin necrosis. Under local anesthesia, a longitudinal incision was made over the proximal DPA. After proximal control, the aneurysm was exposed and the clots were removed. An anterior wall defect of the DPA was confirmed as the cause of the pseudoaneurysm. Because the back-bleeding from the distal DPA was active, ligation of the proximal and distal DPA was performed safely, followed by debridement of the necrotic foot dorsum (Fig. 3). A second operation was performed a few days later by plastic surgeons to cover the skin defect with a cutaneous flap. The postoperative course was uneventful, and no complications such as flap inflammation or toe gangrene were noted. After the 6-month follow-up, she recovered well with no signs of forefoot ischemia. Informed consent was obtained from the patient for publication of this case report and accompanying images.

Fig. 3.

Postoperative image shows the skin deficit after ligation of the dorsalis pedis artery and debridement of the dorsum.

DISCUSSION

A DPA aneurysm remains a rare condition, even in patients suffering from autoimmune diseases such as SLE or systemic vasculitis [6]. Clinical manifestations include a painful mass, acute foot ischemia, edema or rupture [7]. In cases of arteriovenous fistula formation, subcutaneous venous dilation may be evident. The differential diagnosis includes other vascular (e.g., arteriovenous malformations) or orthopedic (e.g., ganglion cyst) abnormalities [8,9]. In the present case, the mass was initially considered a hematoma by the treating physicians, and the pseudoaneurysm was neglected until it reached a very large size and caused a skin necrosis.

For the diagnosis, clinical suspicion is important for a growing pulsating mass after A-line removal. A duplex ultrasound scan, computed tomography angiography (CTA), magnetic resonance angiography (MRA) and digital subtraction angiography can confirm the diagnosis and evaluate the collateral circulation [9]. Duplex ultrasonography is a cost-effective and time-saving diagnostic modality with high accuracy provided the operator is experienced [10,11] and it is the recommended first-line approach. The typical ultrasound appearance is a swirling flow pattern within an echolucent sac (yin-yang sign). CTA and MRA are less invasive techniques that facilitate accurate aneurysm localization and provide accurate dimensions before the planning of a definite treatment. Another advantage of CT/magnetic resonance imaging is that it is not operator-dependent. Digital subtraction angiography is not recommended due to its invasive nature; thus, it is only considered for therapeutic purposes.

Concerning treatment, several strategies have been reported such as ligation, resection and end-to-end anastomosis, reconstruction with venous graft, compression, percutaneous embolization and thrombin injection [1,9]. To determine the proper treatment strategy, perfusion of the distal foot, the presence of underlying peripheral artery, and pseudoaneurysm size and location (possible nerve compression) should be considered [12]. Simple ligation can be performed in cases of good distal perfusion, while patients with inadequate distal perfusion should be treated with arterial reconstruction [6,13]. Small aneurysms could be treated with compression or thrombin injection whereas large aneurysms should be resected to prevent the compression of an adjacent nerve and further neurapraxia [14]. An endovascular strategy was recently introduced in small aneurysms without the risk of compression symptoms [15]. The treatment should be performed without delay to minimize the risk of complications such as rupture or distal embolism.

While the cause of true DPA aneurysms could be related to atherosclerosis, infection, or connective tissue disease, pseudoaneurysms usually occur secondary to trauma [9,16]. Penetrating injuries, fractures, sprains, iatrogenic injuries (ankle arthroscopy, A-line cannulation or endovascular procedures) and infection can cause false aneurysms [12]. In SLE patients, ruptured aneurysms and pseudoaneurysms were mainly reported in splanchnic arteries [17,18]. SLE is an autoimmune disease that can affect any vessel throughout the body, resulting in vessel wall weakening and vasculitis, in up to 56% of the cases [17]. Appel et al. reported a classification of SLE vasculopathy that included non-complicated vascular deposits of immune complexes, non-inflammatory necrotic vasculopathy, thrombotic microangiopathy and true lupus vasculitis [19]. Thus, the assumption that SLE is correlated with true/false aneurysm development has been discussed but not yet elucidated.

In the present case, the primary mechanism of injury was DPA cannulation (with a 22-gauge needle) despite the fact that A-line placement in our hospital is performed only by highly experienced anesthesiologists or intensivists. Moreover, compression of the puncture site for 24 hours after removal is the routine protocol, and false aneurysm formation due to arterial line placement is rarely observed. Given that the possibility of an improper technique or inadequate hemostasis is excluded, we suspect that SLE could have played an important role in this case. A histologic examination may reveal hidden vasculitis in the affected artery; unfortunately, we did not perform a pathologic examination. Therefore, we suggest routine histologic examinations of rare lesions in unusual locations, particularly in patients with autoimmune diseases.

CONCLUSION

A DPA false aneurysm after A-line placement is very rare. However, hidden vasculitis in SLE patients may contribute to the development of pseudoaneurysm. Therefore, physicians should be careful to place an A-line in SLE patients, and the compression after removal should be performed carefully, and serial follow-up is mandatory. In the case of a growing pulsating mass, duplex ultrasonography should be performed to rule out pseudoaneurysm. Prompt surgical treatment is mandatory to prevent serious complications including skin necrosis, distal ischemia, or rupture.