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Renal cell carcinoma in horseshoe kidney with vena caval involvement.

CASE REPORT A 76-year-old man was referred after computerized tomography (CT) detected an 8.4 5.4 cm renal cell carcinoma involving the right moiety and isthmus of a sigmoid-shaped fused kidney during an unrelated sepsis evaluation. On physical examination the patient had a palpable right abdominal mass. No varicocele or lower extremity edema was noted. Seven days before surgery we obtained magnetic resonance angiography and venography (MRA/MRV) to identify the arterial anatomy of the kidney and tumor, as well as to assess the renal veins and inferior vena cava. MRA/MRV revealed a main right renal artery and multiple accessory right renal arteries supplying the right moiety and mass (see figure). Two left main arteries supplied the left moiety. No evidence of venous extension was noted. Chest CT showed no evidence of pulmonary or bony metastasis. We performed right radical nephrectomy and isthmusectomy. At surgery the arterial anatomy and its relationship to renal parenchyma and tumor corresponded precisely to those observed on MRA/MRV. Arteries to the isthmus and right moiety were ligated and divided. We encountered tumor thrombus within a renal isthmus vein that extended into the vena cava for approximately 4 cm. On circumscribing the renal isthmus vein os we found tumor thrombus inseparably adherent to the wall of the inferior vena cava. This finding necessitated replacement o fa5c msegment of the vena cava with polytetrafluoroethylene tube graft. The patient was discharged home on postoperative day 6 after an uneventful postoperative course. Final pathological evaluation demonstrated Fuhrman grade II renal cell carcinoma. Surgical margins were negative. Retrospective review of the MRV with a senior radiologist still failed to identify venous involvement. DISCUSSION Preoperative imaging is crucial in planning the surgical approach in such a case. MRA/MRV and CT angiography have been advocated for imaging arterial anatomy. Aslam Sohaib et al found that MRA/MRV has sensitivity, specificity and accuracy of 100%, 89% and 92%, respectively, in assessing tumor involvement of the vena cava in unfused kidneys.2 In renal donor studies helical CT angiography has been reported to be superior to MRA for renal arterial anatomy.3 While arterial anatomy was well demonstrated in our case, venous involvement was not appreciated preoperatively or in retrospective review of the MRA/MRV. We speculate that imaging for venous involvement may be less accurate in fused kidneys due to smaller caliber renal veins and variable venous anatomy. The surgeon should be prepared for unexpected vascular anatomy despite impressions gained from preoperative imaging.