Among the nine patients in this study, there were six males and three females. The average age is 56.6 years old and the average BMI is 23.4kg/m2. Five cases of primary renal tumors were located on the right side and four cases on the left. Preoperative assessment of the American Society of Anesthesiologists (ASA) was performed in four cases with grade Ⅱ and five cases with grade Ⅲ. IVC tumor thrombus was classified according to the Mayo classification(7), including zero case of Mayo 0, one case of Mayo I, five cases of Mayo II, two cases of Mayo Ⅲ and one case of Mayo Ⅳ.
According to the clinical manifestations of the patients, they were divided into those without obvious clinical symptoms, those with only local symptoms (such as hematuria, low back pain, abdominal mass, etc.), and those with only systemic symptoms (such as fatigue, weight loss, fever, etc.), and those with both local and systemic symptoms. All patients underwent enhanced computed tomography (CT) examination of the urinary system preoperatively to evaluate the side, size of the tumor, whether there were perirenal fat invasion, lymph node metastasis and distant metastasis, and enhanced magnetic resonance imaging (MRI) examination of IVC to identify the characteristics of tumor thrombus. (Fig. 1) The length and width of the IVC tumor thrombus were measured at the coronal position. The presence or absence of bland thrombus (non-neoplastic thrombus) was determined by the delayed phase of enhanced MRI(13). According to the imaging characteristics, whether the tumor thrombus invaded the vascular wall(14) and whether there was a tumor thrombus growing against the direction of venous return were judged.
All patients underwent open surgery. The procedure was as follows. Chevron incision was used when the primary renal tumor was located on the right side. From the xiphoid process to the mid-axillary line at 2cm below the right costal margin, it extended about 10cm below the left costal margin, forming a "herringbone" incision. If the primary renal lesion was located on the left side, the open surgical incision was symmetrical to the right renal tumor incision. Surgical methods for patients with different tumor thrombus grades were as follows. If the Mayo I tumor thrombus was short, IVC tumor thrombus could be squeezed into the renal vein by “milking” technique and downgraded to grade 0. Cut off the renal vein using Hem-o-lok clip at the proximal end. For patients with Mayo II tumor thrombus, the contralateral renal vein, caudal IVC, and cephalic IVC were dissociated and exposed. The caudal IVC, contralateral renal vein, and cephalic IVC were sequentially clamped using the vascular blocking tape. The IVC wall was cut, and the thrombus was removed. If the tumor thrombus was found to invade the IVC wall, it is necessary to segmental resect the invaded vena cava wall(15). For Mayo III patients, several short hepatic veins should be cut and a long enough IVC should be dissociated to provide surgical vision. The ligamentum teres hepatis, left and right triangular ligament, sagittal ligament and coronal ligament were cut off, and the liver was dissociated and turned left. The posterior IVC and hepatic vein were fully exposed. Intraoperative ultrasound can be used to explore the superior pole of tumor thrombus in vena cava. Fully dissociate and expose the liver and the first hepatic portal. The distal IVC of tumor thrombus was blocked first, then the contralateral renal vein, hepatic artery and portal vein were blocked in turn, and finally the proximal IVC was blocked. For Mayo IV patients, the technique of avoiding thoracotomy and cardiopulmonary bypass was selected. The diaphragm was cut longitudinally during operation. The “milking” technique was used to squeeze the atrial tumor thrombus into the IVC with fingers and block the pathway of upward displacement of the tumor thrombus.
According to the nature of tumor thrombus and the degree of vascular wall invasion, IVC surgery was divided into simple IVC thrombectomy, distal IVC transection (retaining the contralateral renal vein back into the IVC), and segmental IVC resection. After cutting the IVC wall during the operation, if the tumor thrombus was filled and completely blocked the IVC, considering the invasion of the IVC wall, a segmental resection of the inferior vena cava was required. For right primary renal tumors with recurrent tumor thrombus in the IVC, 4 − 0 Prolene suture can be used for continuous suture of the left renal vein, the distal end and the proximal end of the IVC during the operation, and the blood can be refluxed only by the branches of the left renal vein. For left primary renal tumor with recurrent tumor thrombus in the IVC, the blood reflux channel from the right renal vein to the distal end of the IVC can be retained, and the proximal end of the inferior vena cava can be sutured. If intraoperative adrenal invasion or metastasis is found, adrenalectomy is needed. Renal hilar lymph node dissection is required during the operation if renal hilar lymph node enlargement is found,
The pathological types of renal cell carcinoma, WHO / ISUP nuclear grading, and whether renal hilar lymph node metastasis were analyzed according to postoperative pathology. The preoperative serum creatinine and 1 week after operation were counted to reflect the changes of renal function before and after operation. The modified Clavien classification system was used to evaluate the postoperative complications(16), among which grades ≥ three were defined as severe complications(17).
The first follow-up was conducted within one month after the operation, focusing on postoperative complications. Then the patients were followed up every 3–6 months, every 6–12 months after 2 years, and every year after 5 years. Patients with residual tumor or postoperative recurrence or distant metastasis were treated with tyrosine kinase inhibitors.