A 59-year-old man presented to our clinic with severe left flank pain after vigorous golfing. The patient exhibited tenderness at the left costovertebral angle. He had a history of hypertension and diabetes, both of which were well-controlled with medication. No recent trauma or endovascular procedures were reported. Laboratory tests showed elevated C-reactive protein (5.3 mg/dL) levels, but complete blood cell counts, creatinine levels, and urinalysis were unremarkable. A serum cholesterol test showed total cholesterol levels of 129 mg/dL, low-density lipoprotein cholesterol levels of 58 mg/dL, and triglyceride levels of 141 mg/dL. Computed tomography (CT) revealed a left renal infarction and the presence of dual left renal arteries with narrowing and irregularity in the left upper renal artery with an intraluminal hematoma, suggesting renal artery dissection. A 1.5-cm aneurysmal dilatation was also noted (Fig. 1A). CT angiography excluded other underlying arteriopathies, such as atherosclerosis, fibromuscular dysplasia, or connective tissue disorders (Fig. 2). Electrocardiogram and 24-hour Holter monitoring revealed normal sinus rhythm without arrhythmias. Echocardiography revealed the absence of intracardiac masses or thrombi. Laboratory tests revealed no abnormalities in coagulation. We suspected that spontaneous renal artery dissection (SRAD) caused the acute infarction in the left kidney. To prevent thrombosis at the site of endothelial damage and propagation of the dissection, anticoagulation was initiated with enoxaparin (1 mg/kg every 12 hours) and switched to oral warfarin. Oral warfarin therapy was continued for 6 months, aiming for an international normalized ratio range of 2 to 3. A follow-up CT scan revealed segmental atrophy of the left kidney, recovery of luminal flow in the dissected left upper renal artery, disappearance of the intraluminal thrombus, and regression of the aneurysm (Fig. 1B). Oral warfarin was discontinued and switched to low-dose aspirin as no thromboembolic risk factors were identified. No recurrence was noted during the 3-month follow-up period. Written informed consent was obtained from the patient for the publication of this report including all clinical images.