Introduction: Distinguishing renal oncocytoma from eosinophilic variant chromophobe renal cell carcinoma (ChRCC) is challenging in clinical practice, particularly when anatomical variants such as bilateral pelvic kidneys are present, as they may cause artifacts or misinterpretation on diuretic renography.
Case presentation: A 52-year-old woman with bilateral ectopic pelvic kidneys presented with a solid mass in the right pelvic kidney. CT angiography revealed a complex vascular pedicle with an accessory renal artery. Preoperative 99mTc-DTPA diuretic renography showed a split renal function of 75% for the right tumor-bearing pelvic kidney and 25% for the left pelvic kidney, without evidence of obstruction. Laparoscopic right radical nephrectomy was performed. Initial histopathology suggested oncocytoma; however, the immunohistochemical profile (CK7+, CD10+, RCC+) supported reclassification as eosinophilic variant ChRCC. One month after surgery, an initial postoperative renogram reported "no visualization" of the left kidney. As the patient was asymptomatic with serum creatinine of 1.5 mg/dL, imaging was reviewed and confirmed a retrovesical pelvic kidney overlapping the bladder in the standard projection. A second renogram in oblique projection with pelvic-centered field showed 72.8% split function, Tmax of 2.0 min and T½ of 13.8 min, without obstruction. eGFR by CKD-EPI 2021 was ~46 mL/min, consistent with CKD stage G3a.
Conclusion: This case highlights (1) the crucial role of immunohistochemistry in differentiating eosinophilic ChRCC from oncocytoma; (2) the importance of recognizing bilateral pelvic kidneys to avoid false-negative interpretation of diuretic renography; and (3) the need to adapt renographic technique (oblique projection, pelvic-centered acquisition or SPECT/CT) for accurate functional assessment of a solitary pelvic kidney.
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Revista Científica
Publicación oficial de investigación científica en urología.
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