It has been proposed that four factors predispose to BAPs, namely increased flow, increased pressure, focal vessel wall weakening, vessel wall injury but the aetiology and pathogenesis are not well understood [4]. They can be classified according to location, divided into mediastinal, intrapulmonary or both [2].
The most comprehensive review to date by Noberto et al in 2018 [5] found 108 cases of bronchial artery aneurysm or pseudoaneurysm reported in the literature with the aetiology unknown in almost one half of cases (49.1% idiopathic). Underlying lung disease such as bronchiectasis (including cystic fibrosis), recurrent infection, silicosis, inflammatory lung diseases and lung cancer are frequently associated [6]. Trauma and iatrogenesis are other important considerations. Vascular risk factors are also important, including atherosclerosis, hypertension, vasculitis and vascular syndromes such as hereditary haemorrhagic telangiectasia (Osler-Weber-Rendu) [5,7]. Anticoagulation may also be contributory. Norberto et al reported a mean age at presentation of 57.9 years (range 15 to 89 years) [5].
Contained pseudoaneurysms without overt rupture tend to be indolent, either asymptomatic and found incidentally on CT with symptoms only elucidated retrospectively [8,9], but may present with dysphagia, discomfort, cough or vague symptoms that raise suspicion of occult malignancy. Ruptured pseudoaneurysms most frequently present with thoracodynia or haemoptysis but can also manifest with acute dyspnoea, compressive effects of mediastinal hematoma, haematemesis, haemothorax or shock depending on the site and extent of haemorrhage [1,10]. Importantly, BAP rupture can result in life-threatening haemorrhage. Rupture into the mediastinum can cause superior vena cava syndrome [11] or mimic aortic dissection [2,7,12]. Intrapulmonary BAPs are most likely to present with haemoptysis [4]. Massive haemoptysis, defined as greater than 300 mL within a 24-hour period, most commonly comes from a bronchial arterial source (>90%) and carries a mortality exceeding 50% [13,14]. The variable size of ruptured BAPs in the literature has led to the inference that diameter is not necessarily an incremental risk factor for rupture [12,15]. It should also be noted that the risk of rupture with false aneurysm is higher than with a true aneurysm, although making the distinction in diagnosis is not always possible [1]. For these reasons, timely diagnosis, early referral and urgent elective treatment is recommended whenever possible, regardless of size or symptomatology [16].
CECT tends to be the first line imaging modality to diagnose and characterise BAPs and guide subsequent treatment. Chest radiography has extremely low sensitivity even in the event of overt rupture. Digital subtraction angiography (DSA) is the gold standard and confirmatory of the diagnosis at the time of endovascular treatment. DSA has a reported sensitivity of 100% compared to CT which is 67% [17]. MRI is another consideration, especially in young patients or the subacute setting, but is limited by cost, availability, time and numerous artefacts [18]. It is recognised that thrombosis of the BAP limits flow and may result in delayed enhancement or non enhancement, thereby confounding the diagnosis [18,19]. The main differential diagnoses on imaging would be a saccular aneurysm arising from the aorta, ductus arteriosus, aberrant right subclavian artery or another aortic branch.
Up to 40% of patients with unilateral vocal cord palsy are asymptomatic at the time of diagnosis and this may be further masked by the presence of other symptoms or other cranial nerves involved with the underlying disease process [20].
The two main treatment options are endovascular repair or open surgery. Whilst they have a comparable success rate (93.1% vs 90.0% respectively), endovascular techniques are recognised as safer, less invasive, less painful, more selective, lower in cost and offer shorter hospital stays and improved quality of life [5,16]. Embolisation is generally accepted as first line, most commonly with coils alone or in combination with liquid embolics such as gelatin sponge, polyvinyl acetate (PVA), cynanoacrylate (glue) or onyx [5]. Placement of an aortic stent-graft is another endovascular option but limits access back into the bronchial arteries if retreatment is required, can be problematic in the setting of infection and is associated with increased cost, time and risk [21,22,23]. Surgery may be considered where there is a contraindication to angioembolisation (e.g. documented iodine anaphylaxis) or where the anatomical configuration makes definitive embolisation impossible [24]. Surgical techniques include pseudoaneurysm excision/resection or ligation (with or without vascular reconstruction depending on collaterals), lobectomy or pneumonectomy [25].
In our reported case, coil embolisation via a microcatheter successfully treated the BPA without the need for adjunctive liquid embolics and without complication.