We present a case of a patient with supranumerary kidney diagnosed after laparoscopic radical nephrectomy. Urinary leakage, an unusual complication that appeared postoperatively, led to complementary examination and making the right diagnosis. The reevaluation of the preoperative CT (computed tomography) in enhancement phase and the new CT scan confirmed the presence of a real accessory organ connected to the main unit with a small bridge of tissue. The latter right nephrectomy was performed. Despite the scarceness of this anomaly, a thorough interpretation of images obtained during investigative procedures can provide a clue about the presence of this rare entity.