Calyceal diverticulum simulating a renal tumor

Calyceal diverticulum (CD) is a rare anatomic anomaly with an incidence of 0.2% to 0.6% in the patients undergoing renal imaging. They are considered benign lesions and malignancy is exceedingly rare. For diagnosis it is suggested to perform a multiphasic contrast-enhanced computed tomography (CT) evidencing a diverticulum of the pelvicalyceal system with thin-walled cavities communicating with the central collecting system. However, they can be usually mistaken as kidney cancers leading to unjustified nephrectomy. Here, we present a case of a 34-year-old patient who underwent surgery in 2022 due to suspected kidney cancer and histopathological analysis surprisingly reported a CD.