Seeming Retroperitoneal tumor (Simple Renal Cyst)

tuab_22a_n.jpg to tuab_22d_n.jpg: 13.9-year-old girl in whom an IVU was performed for work-up of recurrent urinary tract infection. tuab_22a_n.jpg: Enlargement of the upper pole of the right kidney with amputation of the upper calix group in comparison to the left kidney. tuab_22b_n.jpg: Operative findings: Semispheric protrusion of the renal parenchyma laterally to the right upper pole. tuab_22c_n.jpg: It is possible to shell out the cystic structure of the right renal upper pole. tuab_22d_n.jpg: The cystic structure after enucleation. tuab_22a_n.jpg to tuab_22d_n.jpg: The diagnosis is not a Wilms' tumor, but a simple renal cyst which may be reminiscent during work-up (displacement and disconfiguration of the calicopelvic system analogously to a localized nephroblastoma) as well as during surgery (tumorous protrusion of the renal parenchyma) of a Wilms' tumor. The knowledge of this disease entity avoids an unnecessary ephrectomy. In case of recurrent urinary tract infections without another cause and/or of continuous increase of the size of the cyst, and exceeding a critical size with embarassment of the calicopelvic system, an enucleation is indicated. There is no connection with the calicopelvic system, but the latter may be opened during surgery. Simple renal cysts of this type are an example of congenital malformations which may simulate a nephroblastoma and are, therefore, a possible differential diagnosis.