Renal Infarction in a Newly Diagnosed Atrial Fibrillation Patient.

Renal infarction is a rare but potentially serious condition, often misdiagnosed due to its non-specific presentation, which mimics conditions such as nephrolithiasis and pyelonephritis. Discussed in this case report is a 68-year-old woman who presented to an emergency department with two weeks of worsening left flank pain. She was found to have a new diagnosis of atrial fibrillation (AF) on electrocardiogram (ECG) and CT findings revealing renal infarction. The patient was effectively managed with anticoagulation, pain relief, and outpatient vascular surgery follow-up. Early identification was crucial to mitigating complications such as renovascular hypertension and chronic kidney disease. This case underscores the importance of maintaining clinical suspicion for renal infarction in patients presenting with unexplained flank pain in the setting of new-onset AF. Our report highlights the value of a thorough history, physical examination, and timely imaging. These factors ensure both optimal diagnostic accuracy and improved patient-centered outcomes with this rare pathology.