Findings typical of COVID-19 pneumonia have previously been well-described: peripheral-predominant ground-glass opacities (GGO) with and without reticular pattern, consolidation, vacuolar sign, fibrous streaks, vascular dilation, and air bronchogram [11, 12]. In these patients, acute pulmonary thromboembolism occurs with high incidence, particularly in severely ill, hypoxic patients admitted to the ICU. .
Subsegmental vascular enlargement (more than 3 mm diameter) in areas of lung opacity was observed in 89% of patients with confirmed COVID-19 pneumonia . Pulmonary embolism (PE) is more commonly found in the segmental and lobar branches and less commonly in the central pulmonary arteries. Medium to small vessel dilatation is highly prevalent in COVID-19 pneumonia, is not confined to areas of diseased lung, and often involves subpleural vessels, suggesting a diffuse vascular process. Perfusion abnormalities are common features of COVID-19 pneumonia, including mosaic perfusion, focal hyperemia in a subset of pulmonary opacities, focal oligemia associated with a subset of peripheral opacities, and rim of increased perfusion around an area of low perfusion (“hyperemic halo” sign). .
In our review, 12 studies found an incidence of PE ranging from 2.8 to 57%, with patients admitted to the ICU experiencing PE at significantly higher rates [3, 5, 15,16,17,18,19,20,21,22,23,24]. Though isolated COVID-19 infection represented the most common indication for CTPA imaging request, clinically apparent dyspnea, hypoxia or increasing oxygen requirement, chest pain, hemoptysis, and tachycardia, as well as elevated D-dimer, were the most common indications for additional imaging . Cau et al. found that COVID-19 patients with radiographically confirmed PE had concomitant increased pulmonary findings of GGO and consolidation, with a worse CT chest severity score and greater extent of lung lobar involvement. Furthermore, most pulmonary emboli (80%) were found in parenchyma with opacities relating to COVID-19 pneumonia . A majority of PEs occurred in proximal vessels (e.g., lobar or segmental) relative to distal ones (e.g., subsegmental) [17, 21, 25]. Concomitant involvement of other large systemic arteries occurred in a minority of patients . We present several cases of PE associated with aortic thrombus and splenic infarcts (Fig. 3), mycotic pseudoaneurysms of pulmonary artery (Fig. 5), ruptured left renal artery aneurysm (Fig. 6), and central venous line–related DVT of lower extremity veins and psoas hematoma (Fig. 10), as discussed below.
Mycotic (infected) aneurysms, i.e., aneurysmal degeneration of the arterial wall secondary to bacteremia or septic embolization, are classified as true aneurysms (involving intima, media, and adventitia) or pseudoaneurysms (blind saccular outpouching contiguous with the arterial lumen). Mycotic pseudoaneurysms secondary to COVID-19 infection are exceedingly rare but have been associated with high morbidity and mortality [26, 27]. Imaging findings include multilobulated or saccular aneurysm with or without intraluminal thrombus, intramural air or perivascular presence of fluid, soft tissue stranding, and/or air (Fig. 5). These pseudoaneurysms may be complicated by rupture and hemorrhage if not diagnosed and treated promptly. We present a case of bilateral central PE complicated by pseudoaneurysm formation and hemorrhage in the left lobar pulmonary artery. This patient was managed with pulmonary artery stents and Amplatzer plug placement which ultimately achieved stasis and subsequent thrombosis of pseudoaneurysm. In another case (Fig. 5d), a young male who was admitted with COVD-19 pneumonia complicated by necrotizing pneumonia with associated small lung parenchymal pseudoaneurysm likely arising from the subsegmental branch of left lower lobe pulmonary artery. This patient was managed with left lower lobectomy.
Aortic thrombosis is a rare complication of COVID-19 infection and can present asymptomatically or with a consequence of ischemic events. A number of case reports and series have discussed free-floating aortic thrombi in the setting of COVID-19 infection without associated atherosclerosis. In one case, CTA demonstrated an aortic thrombus at the aortic arch without definitive aortic atherosclerosis and associated with splenic infarcts and pulmonary embolism (Fig. 3). In another case, a COVID-19 patient presented with significantly enlarged size of known atherosclerotic plaques in the infrarenal abdominal aorta as compared to prior CT scan 1 year ago suggestive of accelerated process of intimal injury and atherosclerotic soft plaque deposition causing mild aortic stenosis (Fig. 4). These patients are usually managed with anticoagulation therapy as a standard of care unless vascular intervention such as thromboembolectomy is required for larger occlusive thrombus in order to prevent emboli shower [1, 28, 29]. Although rare, these aortic thromboses have also been associated with occlusion of distal end arteries affecting organs such as the kidney and spleen [29,30,31] (Fig. 3).
CTA abdomen and pelvis
The most common indication for acquisition of CTA was abdominal pain, followed distantly by complaint of vomiting and fever. Over half of patients who underwent CT have positive findings, most commonly nonspecific intestinal distension, colorectal and small bowel mural thickening, gallbladder wall thickening, and ascites [32, 33]. By comparison, vascular findings are relatively uncommon as compared to non-vascular findings. COVID-19 patients present with both thrombotic and hemorrhagic adverse events with hemorrhagic events being more common . Hematomas involving the retroperitoneum, abdominal wall, gluteal regions, or upper thigh are the most commonly reported hemorrhagic complication [34,35,36]. Thrombotic events demonstrated on CTA include both occlusion of major arteries and solid organ infarct including, but not limited to, the intestinal tract, kidneys, pancreas, and liver. [32, 34, 37].
Bowel ischemia/infarcts have been described as a rare complication overall in COVID-19 patients but is a more common vascular consequence in the abdomen and pelvis . CTA may demonstrate pneumatosis intestinalis, pneumobilia, pneumatosis portalis, pneumoperitoneum, and variable reactive peritoneal free fluid. Very rarely, vascular occlusion or vasculitis of mesenteric arteries such as branches of celiac axis or superior mesenteric artery (SMA) may be detected. An abdominal-pelvic findings study by Goldberg-Stein demonstrated 15% bowel wall thickening, out of which 6.2% were found in the colon; although mural wall thickening is a non-specific finding, it is suggestive of enteritis or colitis inclusive of microvascular ischemic changes. .
Solid organ infarction and bleeding
Hepatic, renal, and splenic ischemia have been described in association with patients critically ill with COVID-19 . A CT abdomen-pelvis study conducted by Goldberg-Stein found 5% incidence each of splenic and renal infracts out of 141 patients . CTA demonstrates hypoenhancement and wedge-shaped cortical hypodensity of variable sizes (Fig. 3). Infarcts may be large and diffuse, involving the entire organ, or multifocal within a single organ. These are typically acute infarcts and hence might present with organ swelling with hypoenhancement in the early phase of microinfarction and then later might progress to loss of organ volume in the subacute to chronic infarction phase.
Intrapenchymal bleeding within solid organs is less common than infarct and is a rare presentation. We present a case of active bleeding from a ruptured aneurysm of arcuate branch of left renal artery causing large hematoma at upper pole of left kidney extending into retroperitoneum (Fig. 6). There was a concurrent non-occlusive pulmonary embolism in left lower lobar pulmonary artery. Active bleeding was managed with coil placement during superselective left renal artery angiogram.
Gastrointestinal hemorrhage has commonly been described in association with acute COVID-19 infection. We present one such case of active arterial bleeding involving rectum and associated large sigmoid colonic hematoma; the arterial bleeder was arising from inferior rectal branch of internal iliac artery (Fig. 7). While data is limited on which risk factors, patient characteristics, and clinical courses are associated with increased risk of gastrointestinal hemorrhage in COVID-19 patients, some information has been reported. In a meta-analysis of 663 COVID-19 patients, of which 34% presented with gastrointestinal bleeding, Chen et al. found that history of gastrointestinal bleeding was moderately to highly correlated with history of oral anticoagulation .COVID-19 patients who presented with gastrointestinal bleeding had higher mortality rates and had higher risk of gastrointestinal ulcers versus esophagitis on upper GI endoscopy . Goyal et al. further demonstrated that most COVID-19 patients with gastrointestinal bleeding were conservatively managed with therapeutic endoscopy required in only 12.2% of cases and blood transfusion required in approximately 50% of patients . Notwithstanding, some acute gastrointestinal bleeding in unstable patients do require vascular intervention.
Intramuscular and retroperitoneal hematoma
COVID-19-associated small-vessel hemorrhage resulting in musculoskeletal system involvement, notably intra- and peri-muscular hematoma, has been well-described. The most common hematoma site is the iliopsoas involving the retroperitoneum, followed by rectus sheath involving the anterior abdominal wall, pelvic hematoma, hemoperitoneum, and subcapsular organ hematomas [32, 34,35,36, 40,41,42] (Figs. 7–10). Imaging findings include variable size hyperdense mass like hematoma often with blood-fluid hematocrit level depending on the timing of bleed, causing displacement and compression of surrounding structures. If the hematoma is huge, there is also risk of compartment syndrome, more commonly in tighter spaces like extremities and less likely within the abdominal cavity. A subacute hematoma might appear hypodense due to evolution of blood products accumulated over a period of time.
Deep venous thrombosis
Deep vein thrombosis is a prevalent finding in patients with severe COVID-19, with ultrasonography as a primary method of diagnosis. Though true incidence is unknown, Pieralli et al. detected DVT in 13.7% of COVID-19 pneumonia patients screened on ultrasound surveillance protocol; most of these patients were asymptomatic at time of screening. An ultrasound study conducted by Gawande et al. found that out of a total 196 US studies, extremity venous doppler US was the most commonly requested study (51%), and the most common finding was deep vein thrombosis in 18.1% of studies. .
Though bedside ultrasonography (or Doppler) remains a mainstay of initial diagnosis of DVT in the extremities, and has been shown to be diagnostically equivalent to CT venography (CTV), CTV can be performed in patients for whom there is a high clinical suspicion for DVT with simultaneous PE in concert with CTPA without requiring additional contrast material . This provides both direct visualization of thrombi and increased sensitivity in detecting occlusion of thoracic and proximal abdominopelvic veins typically undetectable by US. Chen et al. found significantly lower incidence of DVT on US (4.3%) compared to CTV (82.6%) in patients with mild or moderate COVID-19 pneumonia . The increased sensitivity of CTV compared to doppler US provides validation for the implementation of CTV as an effective and sensible diagnostic modality.
On CTV, typical features of DVT include contrast filling defect with hypodense thrombus, venous distension, rim enhancement of the vein, and perivenous edema or fat stranding (Figs. 8 and 10). Often times DVT in extremities is accompanied by intramuscular hematomas. This combination of thrombosis and hemorrhage is challenging to manage and hematology experts are consulted for titration of anticoagulants and blood transfusion as indicated.
Peripheral arterial thrombosis
Acute thrombosis of peripheral arteries is a rare but critical finding in hospitalized COVID-19 patients. The odds are higher due to hypercoagulable state, relative immobility, and increased vascular access requirement in hospitalized COVID-19 patients. Ogawa et al. first illustrated large vessel peripheral extremity occlusion in association with findings of COVID-19 pneumonia in a case series of 9 patients, even in absence of preexisting hypercoagulable state or calcific atherosclerotic disease . The authors found that there was no correlation between the length of arterial occlusion and the severity of COVID-19 pneumonia. A longer length of about 10 cm arterial occlusion was seen in patients with lower extremity involvement. They also found that a pre-existing calcified atherosclerotic plaque within the vessel wall was not necessarily contributing to increased risk of thrombotic arterial occlusion. Both Ogawa et al. and Goldman et al. showed that due to great thrombus burden in extremity arteries there is increased likelihood of open thrombectomy, amputation, or death in patients with COVID-19.  We present a case of acute non-occlusive arterial thrombus in the proximal right common femoral artery with associated similar characteristic thrombus in the abdominal aorta. This patient underwent right iliofemoral thromboendarterectomy with bovine pericardial patch angioplasty during initial admission which was complicated by a large postoperative pseudoaneurysm (Fig. 9). This patient also had an acute thrombus formed in the abdominal aorta, which might have been the source of embolism to the right lower extremity.
Vascular access–related complications
Due to immediate viral- and cytokine-mediated vascular changes, COVID-19 patients are at particularly high risk of complications from otherwise low-risk interventions. Though uncommon, vascular access–related complications represent an underrecognized source of morbidity in these vulnerable patients.
In a large-scale retrospective study of vascular access in COVID-19 patients, Gidaro et al. found catheter-related thrombosis (CRT) occurred in 42 (1.9%) of cases . In other studies, most identified cases occurred in peripheral veins and in the context of hemodialysis [49,50,51,52,53,54]; rare cases of CRT secondary to central venous catheter thrombosis have also been described [55, 56]. Though vascular access devices are especially prone to thrombosis, patients with a requirement for long-term vascular access may benefit from a low-dose heparinized saline protocol. .
We illustrate a case of venous line-related thrombus in the right common femoral vein and infrarenal IVC; note inhomogeneous thrombus adhering to the central venous line partially occluding the veins involved (Fig. 10). This same patient had concurrent left psoas hematoma and segmental PE. The patient was initiated on anticoagulation but unfortunately passed away a week after the scan.
Pseudoaneurysm related to intervention
Iatrogenic pseudoaneurysm is an exceedingly rare complication; Al-Thani et al. presented one case of subclavian artery pseudoaneurysm induced by central venous catheter insertion . The vessel wall weakness due to underlying endotheliitis secondary to both the COVID-19 virus itself in addition to vascular intervention/procedures might be the causative factor. We present a rare case of a large pseudoaneurysm of the right common femoral artery secondary to thrombectomy (Fig. 9). A careful scrutiny of vasculature should be performed on CTA to look for vessel wall irregularities and small outpouchings as these can lead to catastrophic bleeding events.