Acute Renal Artery Thrombosis Following Delayed Postoperative Anticoagulation in Atrial Fibrillation: A Case Report Supporting Apixaban Monotherapy.

Renal artery thrombosis is a rare but potentially devastating vascular emergency, often misdiagnosed due to its nonspecific symptoms. Atrial fibrillation (AF) is a well-known cause of systemic thromboembolism, yet embolisation to the renal arteries remains uncommon. Timely recognition and appropriate anticoagulation are essential to minimise irreversible renal injury. We report the case of an 84-year-old woman with a history of AF (CHA2DS2-VASc score of 5) who developed acute unilateral renal artery thrombosis shortly after undergoing a unilateral mastectomy with sentinel lymph node biopsy. Anticoagulation with apixaban had been appropriately held preoperatively due to bleeding risk, but its resumption was delayed until five days postoperatively. The patient presented with acute flank pain, hypertension, and an acute kidney injury on postoperative day five. A CT abdomen pelvis confirmed a left renal artery thrombosis. Remarkably, a CT angiogram of the whole aorta, performed within 24 hours of restarting apixaban, showed resolution of the thrombus, although renal function did not improve by discharge. This case contributes to the limited but growing body of literature suggesting that direct oral anticoagulant (DOAC) monotherapy, specifically apixaban, is effective in managing renal artery thrombosis. It also reinforces the need for clinicians to consider the timely resumption of anticoagulation and to carefully reassess perioperative management in high-risk AF patients to prevent irreversible thromboembolic complications.