白色的箭头指示肾静脉血栓，肾静脉血栓形成有很多原因：创伤、受肿瘤压迫、肾细胞癌侵犯肾静脉、膜性肾小球肾炎引起的肾病综合征等。
The white arrow marks a renal vein thrombus. There are a host of etiologies for renal vein thrombosis, including trauma, compression by neoplasms, renal vein invasion by renal cell carcinoma, and nephrotic syndrome with membranous glomerulonephritis.
