Teaching Case

A 51-year-old male presented to the Emergency Department with a painful swelling on the thoracic wall in the right infraclavicular region. He had undergone cardiopulmonary bypass eight months earlier as part of a supra-coronary ascending aortic repair to address a type A aortic dissection. The postoperative course was uneventful.

Ultrasound examination revealed a thick-walled heterogeneous fluid collection and no blood flow on colour-Doppler evaluation (Figures 1a and 1b). Computed tomography angiography (CTA) showed a small tubular outpouching arising from the anterior aspect of the distal segment of the right subclavian artery without contrast material extravasation (Figures 2a, 2b and 2c). Additionally, a non-enhancing hypoattenuating collection was observed in the infraclavicular region surrounding this tubular arterial outpouching. The collection extends to the subcutaneous tissue coinciding with the clinically detected lump (Figures 2a, 2b and 2c). Retrospectively, a CTA scan obtained after surgery revealed a small haematoma in the same area (Figures 3a and 3b). In the follow-up surveillance CTA, the collection had completely resolved, but a tubular protrusion arising from the right subclavian artery with a spontaneous hyperattenuating rectangular edge persisted. This tubular protrusion represents the residual surgical side-graft material (Figures 4a and 4b).

In patients who have undergone cardiopulmonary bypass, the evaluation of vascular structures can be particularly challenging due to the presence of surgical material/postsurgical changes. The evaluation of the patient's clinical and surgical history is essential to differentiate normal postprocedural changes from subclavian artery abnormalities [1]. Computed tomography angiography (CTA) plays a crucial role in assessing the subclavian artery as it helps delineate the extent of the vascular lesion and evaluate the surrounding structures [3,4].

Postsurgical changes resulting from subclavian artery bypass can mimic pseudoaneurysms or contrast material extravasation, which are imaging indicators of vascular injury [1]. Pseudoaneurysms of the subclavian artery can result from iatrogenic traumatic punctures, penetrating or blunt trauma often associated with clavicle or first rib fractures [3,4]. CTA findings of subclavian artery pseudoaneurysms include eccentric outpouching of the artery wall, irregular wall contour, partial or complete thrombosis, and haemorrhage with contrast extravasation adjacent to the damaged artery [1]. Patients may present with pain, swelling, or a pulsatile mass in the infraclavicular or supraclavicular area. Compression of adjacent structures, such as the brachial plexus or the subclavian vein, can result in neurological deficits or venous congestion, respectively [3,4].

In surgical procedures requiring temporary arterial access, side grafts (arterial conduits) are commonly utilised, particularly during cardiopulmonary bypass for ascending or aortic arch repairs [1,2]. After the side graft procedure, the arterial conduit is sealed, and it is not removed. Residual side grafts seen on unenhanced CT imaging exhibit distinct features, including a square shape with sharp margins and hyperattenuating suture material or pledgets to support the vessel closure [1,2].

In this patient, the infraclavicular lump was surgically explored and confirmed to be a purulent collection that likely developed from a postoperative haematoma. The subclavian artery’s wall tubular outpouching, first interpreted as a pseudoaneurysm, was, in fact, a short segment of the side graft from the previous ascending aortic surgery and was not mentioned during the abscess drainage procedure as it was a normal postoperative finding.

In conclusion, typical findings on postoperative CT scans after subclavian artery side graft cannulation include the presence of a large metallic clip at the base of the side graft and a residual spontaneously hyperattenuating stump. Radiologists should be aware of post-surgical changes in the subclavian artery to avoid erroneous diagnosis of potential mimics, and for that, obtaining non-contrast images is mandatory.

All patient data have been completely anonymised throughout the entire manuscript and related files.