Tx and Followup:
Laparoscopic left partial nephrectomy preformed along with follow-up imaging.
Renal cell carcinoma, the most common primary tumor of the kidney, is found incidentally in many patients with the widespread use of cross-sectional imaging. In fact, as many as one-half of renal cell carcinomas are discovered incidentally at early stages when they are asymptomatic. CT has also played an essential role in staging renal cell carcinoma in order to guide prognosis and surgical planning. The patient in this case underwent partial nephrectomy for his renal cell carcinoma. As a result, this case generates several interesting questions. What is the standard protocol for staging renal cell carcinoma with CT? What staging systems exist for renal cell carcinoma and what are their differences? Finally, what factors determine the use of radical nephrectomy versus nephron-sparing surgical techniques?
Once a renal cell carcinoma is suspected incidentally, there is a standard protocol for work-up using CT. First, an unenhanced CT is preformed to use as a baseline once intravenous contrast material is administered. Due to a significant vascular supply, renal cell carcinomas enhance following administration of contrast. 12 HU of enhancement suggest possible malignancy. Following the administration of contrast, images are obtained during the corticomedullary phase, nephrographic phase, and excretory phase.
The corticomedullary phase occurs between 25 and 70 seconds after injection and primarily enhances the renal cortex. While not perfect for detecting small lesions, this phase can aid in diagnosing venous extension of the tumor. The nephrographic phase, which occurs between 80 and 180 seconds following injection, is best for detecting renal masses and analyzing indeterminate lesions. Finally, the excretory phase begins 180 seconds following injection and helps evaluate the collecting system, as well as the calices and renal pelvis.
Renal cell carcinoma has two potential staging systems: the Robson classification and the TMN classification. CT is reported to be 91% accurate in staging renal cell carcinoma. The TMN classification is considered more precise because of its clear definition of the anatomic extent of the tumor. With respect to the TMN classification, T1 is reserved for tumors less than 7 cm and T2 for tumors greater than 7 cm. T3 is broken down into three groups based on tumor position. T3a indicates spread to the perinephric fat. T3b indicates that the tumor is present in the renal vein only. T3c describes a tumor in the infradiaphragmatic IVC. T4a and T4b describe tumors with direct invasion of adjacent organs and presence in the supradiaphragmatic IVC, respectively. N1-3 are reserved for regional lymph node metastases and M1a-d for distant metastases.
The Robson classification is staged I-IV. I is given to a tumor confined within the renal capsule. II indicates spread to the perinephric fat. IIIA describes the presence of a venous thrombus, whereas IIIB describes regional lymph node metastases. IVA indicates direct invasion of adjacent organs and IVB indicates distant metastases. An important downfall of the Robson classification is that it uses stage III to describe both patients with venous extension alone and patients with regional lymph node metastases. The treatment for these two groups of patients varies significantly. Venous extension of the tumor can be treated surgically, whereas lymph node metastases indicate a need for palliative therapy.
Due to the rapid increase in incidental discovery of renal cell carcinoma, many tumors are small in size and early-stage. Therefore, nephron-sparing surgery is often an option. The procedure consists of excision of the renal tumor and obtaining 0.5 cm margins of normal renal tissue and preserving the largest amount of functioning renal parenchyma. This procedure is particularly desirable when radical nephrectomy would lead to dialysis. Therefore, it is indicated in patients with a solitary functioning kidney, compromised renal function, or bilateral tumors. In addition, data indicates that small <4 cm in diameter lesions, which are polar, cortical, and a safe distance away from the renal hilum and collecting systems, have similar survival rates for the nephron-sparing procedure and radical nephrectomy. The size and position of the patientâ€™s tumor in this case made him a good candidate for the nephron-sparing procedure.