ObjectiveTo summarize the diagnosis, surgical management, and outcomes of one case of complex unilateral renal artery aneurysm repaired by in situ open surgery. MethodTo retrospectively analyze the clinical data of a patient with complex renal artery aneurysm admitted to the author’s hospital department in December 2021 who underwent in situ open surgery. ResultsThe patient was a middle-aged female with a left renal artery aneurysm detected on physical examination. The renal artery three-dimensional CT imaging showed that the aneurysm was large in size and complex in anatomical structure; the aneurysm was located at the renal hilum, demonstrating multiple outflow tracts and close proximity to renal parenchyma and the ureter. Surgical management included in situ aneurysm resection combined with renal artery branch reconstruction and great saphenous vein bypass grafting. The operation duration was 5 hours with intraoperative urine output was 250 mL, and the intraoperative blood loss was about 400 mL. Four units of erythrocyte suspension, 200 mL of autologous recycled blood, and 400 mL of plasma were transfused during the operation. The results of the 36-month postoperative follow-up showed that the reconstructed renal arterial branches and the bridging vessel had satisfactory blood flow, and renal function was unaffected. ConclusionsThe results of this case suggest that in complex renal artery aneurysms involving multiple branches, in situ resection of the aneurysm followed by revascularization and main renal artery bypass grafting to restore flow is safe and feasible, and the long-term prognosis is good. However, it should be emphasized that the anatomy of renal artery aneurysms should be evaluated in detail preoperatively to determine the method of in situ revascularization. The results of the study also need to be further validated by larger samples and multicenter studies.