Silent Culprit Revealed: Renal Infarction Unmasking Atrial Fibrillation.

Renal infarction is an uncommon yet clinically significant cause of acute flank pain that is frequently misdiagnosed due to its non-specific presentation. Delayed recognition can result in permanent renal damage and missed identification of underlying cardioembolic sources, increasing the risk of recurrent systemic embolization. We report the case of a 73-year-old man who presented with acute-onset flank pain and intermittent dizziness. Early imaging with contrast-enhanced computed tomography revealed multiple infarcts in the left kidney, confirming the diagnosis of renal infarction. Initial electrocardiography did not demonstrate atrial fibrillation. However, given the absence of an obvious precipitating cause, the patient was admitted for further evaluation and continuous cardiac telemetry monitoring. Subsequent inpatient monitoring revealed paroxysmal atrial fibrillation (PAF), establishing a cardioembolic etiology. Laboratory evaluation initially suggested a hypercoagulable state, which was later attributed to heparin initiation rather than a primary thrombophilic disorder. Anticoagulation therapy with heparin was continued to reduce the risk of further thromboembolic events. This case underscores the importance of early recognition of renal infarction symptoms and prompt diagnostic imaging. It also highlights the limitations of a single electrocardiographic assessment, as PAF may remain undetected without continuous telemonitoring. Identifying atrial fibrillation as the underlying cause is critical to prevent recurrent embolic complications, including additional renal infarcts or cerebrovascular events. Early hospital presentation, timely imaging, and prolonged cardiac monitoring are essential in unexplained renal infarction to diagnose occult atrial fibrillation and initiate appropriate anticoagulation, thereby preventing further systemic complications.