What is the management of infrarenal aortic thrombus (blood clot in the lower part of the aorta) affecting kidney function?

Management of Infrarenal Aortic Thrombus Affecting Kidney Function

Immediate Anticoagulation and Hemodynamic Assessment

Initiate immediate anticoagulation with intravenous unfractionated heparin (bolus 5000 IU or 70-100 IU/kg, followed by continuous infusion adjusted to maintain aPTT in therapeutic range) or subcutaneous low molecular weight heparin (enoxaparin 1 mg/kg twice daily) to prevent thrombus propagation and further embolization. 1

Initial Stabilization

• Administer analgesia and intravenous fluids immediately upon clinical diagnosis 1
• Address acidosis and hyperkalaemia if present, as these may indicate significant tissue ischemia 1
• Monitor creatinine kinase (CK) and myoglobin levels, as elevations indicate rhabdomyolysis and predict risk of kidney failure and mortality 1

Hemodynamic Classification and Treatment Algorithm

Hemodynamically Stable Patients

For hemodynamically stable patients with infrarenal aortic thrombus and renal involvement, proceed with urgent imaging (CTA, MRA, or DSA) followed by endovascular intervention as first-line therapy. 1

• Perform diagnostic imaging (CTA, DUS, or contrast-enhanced MRA) to assess thrombus burden, renal artery involvement, and anatomical suitability for intervention 1
• Consider catheter-directed thrombolysis (CDT) or mechanical thrombectomy for acute presentations with preserved renal function 1
• Angiography with super-selective angioembolization should be considered for active bleeding complications, though this is less relevant for primary thrombotic occlusion 1

Hemodynamically Unstable Patients

Hemodynamically unstable patients (WSES Class IV) require immediate surgical intervention with open thrombectomy or bypass grafting. 1

• Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) may serve as a bridge to definitive surgical intervention in unstable patients 1
• Fogarty catheter thrombectomy alone is frequently ineffective for infrarenal aortic thrombosis; axillobifemoral bypass may be necessary in high-risk patients 2
• Surgical treatment should ideally be performed in a hybrid operating room with angiographic capability to assess completion and initiate local lysis if residual thrombus is visualized 1

Renal Protection Considerations

Monitoring Renal Function

• Baseline and serial creatinine measurements are essential, as infrarenal aortic occlusion can threaten renal perfusion through proximal thrombus propagation 3
• However, historical data suggests that infrarenal aortic occlusion does not uniformly lead to suprarenal thrombus propagation or renal dysfunction in all cases 3

Bilateral Renal Artery Involvement

When bilateral renal artery thrombosis complicates infrarenal aortic thrombus, thrombolysis and/or thrombectomy are indicated regardless of hemodynamic status. 1

• This represents an organ-threatening condition requiring aggressive intervention 1
• Unilateral renal artery thrombosis also warrants antithrombotic treatment, though with slightly less urgency 1

Anticoagulation Strategy

Acute Phase Management

• Unfractionated heparin is preferred initially due to its rapid reversibility and ease of monitoring via aPTT or anti-Xa activity (therapeutic range 0.30-0.70 IU/ml) 4
• LMWH is an acceptable alternative with expected anti-Xa activities of 0.5-1.1 IU/ml at 4 hours post-dose for twice-daily dosing 4
• Monitor for heparin-induced thrombocytopenia (HIT), though risk is ten-fold lower with LMWH compared to unfractionated heparin 4

Long-Term Anticoagulation

Continue therapeutic anticoagulation for a minimum of 3 months following successful revascularization, with consideration for extended duration based on underlying etiology and residual thrombus burden. 1

• Transition to oral anticoagulation (warfarin with INR target 2.0-3.0, or direct oral anticoagulants) after acute phase 1
• A case report demonstrated complete resolution of a 10-cm aortic thrombus after 10 weeks of therapeutic anticoagulation (IV heparin followed by warfarin with INR 3.0-4.0), suggesting medical management may be viable in select poor surgical candidates 5

Follow-Up and Surveillance

Post-Intervention Monitoring

• Investigate the etiology of thrombosis: perform Holter-ECG, echocardiogram, and aortic imaging to identify cardioembolic sources or prothrombotic conditions 1
• Consider evaluation for antiphospholipid syndrome and vasculitis if clinically suspected 1
• Ensure optimal medical therapy including statin therapy, which improves outcomes after revascularization 1

Long-Term Surveillance

• Clinical and radiologic follow-up is recommended to assess for recurrent thrombosis or progression of underlying atherosclerotic disease 1
• Serial renal function monitoring (creatinine) should continue, as delayed deterioration can occur even without immediate suprarenal propagation 3

Critical Pitfalls to Avoid

• Do not delay anticoagulation while awaiting imaging in stable patients, as thrombus propagation can rapidly compromise renal perfusion 1
• Avoid Fogarty thrombectomy as sole intervention in infrarenal aortic thrombosis, as it has poor efficacy; definitive bypass or endovascular therapy is usually required 2
• Do not assume renal function is safe simply because thrombus is infrarenal; proximal propagation and embolic complications can still occur 3
• Recognize that advanced age and severe cardiopulmonary comorbidities significantly increase mortality risk (up to 60% in some series), necessitating careful risk-benefit assessment for surgical intervention 2